[His Word 1st]

Hi everyone!

I've got a 2007 GMC c4500 TopKick box truck that's got batteries draining increasingly faster than before.

Liftgate (MBB 3300 lb capacity - it is the back of the box itself) was very slow to open and/or stalled completely and when fully closing back up. Noticed the liftgate light would come on even when it was turned off...the mechanic said it sounds like it could be a solenoid issue - he's the one medium truck mechanic here in town and has about a month lead time required to bring in my truck.

Got a maintainer/charger and hooked it up. During a trip the truck made a ding ding ding repeatedly warning noise and the battery indicator came on and it shut off the truck on the freeway repeatedly. I could start it back up and get down a bit further and it would just do it again and again. This happened after charging about one full day.

Then today I went to head out after having it on the maintainer for 3-4 days straight and it's back to the ding ding ding battery indicator light coming on and the truck shuts off. I have an appointment for it to be dealt with by a mechanic but now don't know that I'll be able to drive it there...

This trip today needs to happen. If you know what to do here and it isn't too complex to explain to a guy who doesn't know all that much about these trucks, please advise me as to how I can get this issue resolved.

Thank you all and God bless you in the name of the Lord Jesus Christ, King of kings.

 

[His Word 1st]

Also, the oil change light is on and it's time for an oil change which I'll be tackling today...if that's at all relevant? I've heard fuel injectors are often a big source of challenges for these trucks but I have no idea how to do anything related to them.

 

[Melonhead1102]

You have bad battery/batteries and possibly a bad alternator. Pull the batteries and go to Autozone/Advanced Auto Parts/O'Reilly etc and have them test the batteries for you.

If you need to replace them, replace both batteries. It's not a good idea to replace them individually because you'll always be capped at the performance of the one with the lowest charge.

 

[His Word 1st]

You have bad battery/batteries and possibly a bad alternator. Pull the batteries and go to Autozone/Advanced Auto Parts/O'Reilly etc and have them test the batteries for you.

If you need to replace them, replace both batteries. It's not a good idea to replace them individually because you'll always be capped at the performance of the one with the lowest charge.

I've got three Interstate batteries connected now and months ago when it was colder and the truck wouldn't start, they'd been tested and charged up from totally dead to full power then.

With the liftgate operating super slowly at the immediate opening and fully closing positions, along with the light for the liftgate coming on when it's in the off position, there isn't any wiring issue or solenoid issue at all then? It could all be due to the alternator? Is that correct?

Thank you for your help!

 

[Melonhead1102]

It does sound like you have a power draw somewhere, but if your batteries are draining while you're driving, you either have a problem with your batteries not taking a charge, or your alternator isn't putting out enough power to keep them charged.

That liftgate is also part of the problem, especially if it's turning on when it should be off, but I really think that you have an issue with the batteries and/or alternator. Once the truck is started you shouldn't be having problems keeping the truck running. Sitting for a little bit and not starting I would definitely think your problem is just with the liftgate and a big power draw. Losing charge while the truck is driving down the highway is a charging system problem.

Take this with a grain of salt; I am NOT anything more than an enthusiast and definitely not a trained mechanic.

 

[His Word 1st]

They told me they can test the alternator also but I guess I'll have to figure out how to remove it to get it there for testing - since the truck dies when I start it at this point, and then I can have both all of the batteries and the alternator tested.

Thank you for your help and God bless you in the name of the Lord Jesus Christ.

 

[jdwarren]

It does sound like you have a power draw somewhere, but if your batteries are draining while you're driving, you either have a problem with your batteries not taking a charge, or your alternator isn't putting out enough power to keep them charged.

That liftgate is also part of the problem, especially if it's turning on when it should be off, but I really think that you have an issue with the batteries and/or alternator. Once the truck is started you shouldn't be having problems keeping the truck running. Sitting for a little bit and not starting I would definitely think your problem is just with the liftgate and a big power draw. Losing charge while the truck is driving down the highway is a charging system problem.

Take this with a grain of salt; I am NOT anything more than an enthusiast and definitely not a trained mechanic.

They told me they can test the alternator also but I guess I'll have to figure out how to remove it to get it there for testing - since the truck dies when I start it at this point, and then I can have both all of the batteries and the alternator tested.

Thank you for your help and God bless you in the name of the Lord Jesus Christ.

I like @Melonhead1102's reasoning but I think we need to get down to just one variable in the equation first. Disconnect the liftgate as far upstream (at the battery or alternator or wherever the main supply is) as possible and see if the problems continue. Remember to disconnect the switch itself as well (presumably that switch flips a solenoid that opens/closes the main circuit, but the switch itself is likely powered from another location, like an accessory fuse panel). If the issues go away then the batteries and charging system are likely fine. If they persist, then deal with that first and see what happens.

One bit of information you could provide that would help is how the main power supply to the liftgate is wired. Is it an "always hot" connection upstream of the solenoid that controls the power to the liftgate? Or is it wired off an ignition-switched accessory circuit? If the latter, then what might be happening is that the solenoid is stuck closed (which would explain the liftgate light staying on), but it only drains the system when the ignition is on accessory or running (which would explain it being able to start after sitting for a while, which I'm assuming is the case because you didn't explicitly state that it won't start -- can you provide clarification on this?).

The above is pretty tough to believe though, because the amount of amperage that thing would have to be sucking to actually stall the truck out is so high that it would almost certainly blow a fuse.

*Edit: I'm not sure about that last point, now that I think of it. An older truck with a 150A alternator probably can't supply 100A (I'm assuming that's about what a liftgate circuit is fused for?) at idle, so it seems reasonable to me that a misbehaving 100A solenoid could potentially cause these problems, assuming it's supplied from a switched power supply (otherwise, it would just smoke the batteries after you shut off the truck and it would never start on its own).

 

[His Word 1st]

I like @Melonhead1102's reasoning but I think we need to get down to just one variable in the equation first. Disconnect the liftgate as far upstream (at the battery or alternator or wherever the main supply is) as possible and see if the problems continue. Remember to disconnect the switch itself as well (presumably that switch flips a solenoid that opens/closes the main circuit, but the switch itself is likely powered from another location, like an accessory fuse panel). If the issues go away then the batteries and charging system are likely fine. If they persist, then deal with that first and see what happens.

One bit of information you could provide that would help is how the main power supply to the liftgate is wired. Is it an "always hot" connection upstream of the solenoid that controls the power to the liftgate? Or is it wired off an ignition-switched accessory circuit? If the latter, then what might be happening is that the solenoid is stuck closed (which would explain the liftgate light staying on), but it only drains the system when the ignition is on accessory or running (which would explain it being able to start after sitting for a while, which I'm assuming is the case because you didn't explicitly state that it won't start -- can you provide clarification on this?).

The above is pretty tough to believe though, because the amount of amperage that thing would have to be sucking to actually stall the truck out is so high that it would almost certainly blow a fuse.

*Edit: I'm not sure about that last point, now that I think of it. An older truck with a 150A alternator probably can't supply 100A (I'm assuming that's about what a liftgate circuit is fused for?) at idle, so it seems reasonable to me that a misbehaving 100A solenoid could potentially cause these problems, assuming it's supplied from a switched power supply (otherwise, it would just smoke the batteries after you shut off the truck and it would never start on its own).

I'm not sure of where the switch is that connects the liftgate to the battery or alternator or elsewhere so I just got under the truck and took some pictures that could help you in helping me find the power draw...one detail that is unusual about my truck (from what I understand) is that the truck must be running in order for the liftgate to operate...so it may be wired into the ignition? Also the light that is supposed to turn on when the liftgate is switched on does not stay lit - it seems that after I'm able to use the liftgate and then close it, the switch will be then turned off but the light will turn on and off and so on intermittently.

I had it powered up fully after three days (according to the maintainer) and drove two hours or so and left it running for a little over an hour loading the box and then a short drive later and the battery light came on and ding ding ding repeatedly until the truck stopped working on the freeway. Then I restarted it probably five times in order to get to my next stop and was able to plug in the maintainer around two hours and then praise God I was able to make it another near two hours without the indicator light or ding ding ding shutdown happening! Hopefully restarting consecutively after repeated shutdowns does not damage/destroy the batteries...

I was also wondering if the function of the liftgate can be made independent from the truck running...? That's obviously later though!

 

[His Word 1st]

I like @Melonhead1102's reasoning but I think we need to get down to just one variable in the equation first. Disconnect the liftgate as far upstream (at the battery or alternator or wherever the main supply is) as possible and see if the problems continue. Remember to disconnect the switch itself as well (presumably that switch flips a solenoid that opens/closes the main circuit, but the switch itself is likely powered from another location, like an accessory fuse panel). If the issues go away then the batteries and charging system are likely fine. If they persist, then deal with that first and see what happens.

One bit of information you could provide that would help is how the main power supply to the liftgate is wired. Is it an "always hot" connection upstream of the solenoid that controls the power to the liftgate? Or is it wired off an ignition-switched accessory circuit? If the latter, then what might be happening is that the solenoid is stuck closed (which would explain the liftgate light staying on), but it only drains the system when the ignition is on accessory or running (which would explain it being able to start after sitting for a while, which I'm assuming is the case because you didn't explicitly state that it won't start -- can you provide clarification on this?).

The above is pretty tough to believe though, because the amount of amperage that thing would have to be sucking to actually stall the truck out is so high that it would almost certainly blow a fuse.

*Edit: I'm not sure about that last point, now that I think of it. An older truck with a 150A alternator probably can't supply 100A (I'm assuming that's about what a liftgate circuit is fused for?) at idle, so it seems reasonable to me that a misbehaving 100A solenoid could potentially cause these problems, assuming it's supplied from a switched power supply (otherwise, it would just smoke the batteries after you shut off the truck and it would never start on its own).

I'm not sure of where the switch is that connects the liftgate to the battery or alternator or elsewhere so I just got under the truck and took some pictures that could help you help me to find the power draw...one detail that is unusual about my truck (from what I understand) is that the truck must be running in order for the liftgate to operate.

I was also wondering if the function of the liftgate can be made independent from the truck running...? That's obviously later though!

 

[His Word 1st]

I like @Melonhead1102's reasoning but I think we need to get down to just one variable in the equation first. Disconnect the liftgate as far upstream (at the battery or alternator or wherever the main supply is) as possible and see if the problems continue. Remember to disconnect the switch itself as well (presumably that switch flips a solenoid that opens/closes the main circuit, but the switch itself is likely powered from another location, like an accessory fuse panel). If the issues go away then the batteries and charging system are likely fine. If they persist, then deal with that first and see what happens.

One bit of information you could provide that would help is how the main power supply to the liftgate is wired. Is it an "always hot" connection upstream of the solenoid that controls the power to the liftgate? Or is it wired off an ignition-switched accessory circuit? If the latter, then what might be happening is that the solenoid is stuck closed (which would explain the liftgate light staying on), but it only drains the system when the ignition is on accessory or running (which would explain it being able to start after sitting for a while, which I'm assuming is the case because you didn't explicitly state that it won't start -- can you provide clarification on this?).

The above is pretty tough to believe though, because the amount of amperage that thing would have to be sucking to actually stall the truck out is so high that it would almost certainly blow a fuse.

*Edit: I'm not sure about that last point, now that I think of it. An older truck with a 150A alternator probably can't supply 100A (I'm assuming that's about what a liftgate circuit is fused for?) at idle, so it seems reasonable to me that a misbehaving 100A solenoid could potentially cause these problems, assuming it's supplied from a switched power supply (otherwise, it would just smoke the batteries after you shut off the truck and it would never start on its own).

Is it the metal rectangular piece attached at the positive pole of the first battery, shown left to right or bottom to top because of picture orientation? I think the yellow and black smallest wires on the negative pole of that same lowest left battery are the lights inside the box - at least it's what I'd assumed anyhow.

 

[jdwarren]

Is it the metal rectangular piece attached at the positive pole of the first battery, shown left to right or bottom to top because of picture orientation? I think the yellow and black smallest wires on the negative pole of that same lowest left battery are the lights inside the box - at least it's what I'd assumed anyhow.

Based on your earlier post (in which you specified that the liftgate only runs when the truck is running) it sounds like there may be something to my hypothesis of the solenoid draining power while the engine is running, but not when it's turned off. I can't make out which of those wires is supplying power to the liftgate, but if you can find it, try disconnecting it (and tucking it away and/or insulating it to make sure it doesn't make intermittent contact or short anything else out) or, better yet, just remove the fuse. Then see if your issues subside and let us know the outcome.

 

[His Word 1st]

Based on your earlier post (in which you specified that the liftgate only runs when the truck is running) it sounds like there may be something to my hypothesis of the solenoid draining power while the engine is running, but not when it's turned off. I can't make out which of those wires is supplying power to the liftgate, but if you can find it, try disconnecting it (and tucking it away and/or insulating it to make sure it doesn't make intermittent contact or short anything else out) or, better yet, just remove the fuse. Then see if your issues subside and let us know the outcome.

So I can simply remove the fuse to the liftgate and remove it and that will test if the batteries are being drained by it or something else, is that right? Is it labeled? Is there a way to know easily which fuse (or wire) is the correct one?

 

[jdwarren]

So I can simply remove the fuse to the liftgate and remove it and that will test if the batteries are being drained by it or something else, is that right? Is it labeled? Is there a way to know easily which fuse (or wire) is the correct one?

Yes to the first question. The fuse to the liftgate is probably not in any actual fuse panel since it's an aftermarket/upfitter device. However, it should be relatively easy to find because it's probably a high amperage circuit; I estimate it has to be 100A or greater. That is not a little ATC style fuse, but rather an ANL or Megafuse or something along those lines. There will probably be a large fuse block near the batteries. Here's an example of what to look for; this is an ANL fuse holder with a 300A fuse I installed for my inverter.

I recommend disconnecting the negative cable from the battery bank before you remove this fuse, because if you don't, then if your ratchet or wrench touches the body of the truck as you're removing it, you'll create a massive short circuit.

 

[His Word 1st]

Yes to the first question. The fuse to the liftgate is probably not in any actual fuse panel since it's an aftermarket/upfitter device. However, it should be relatively easy to find because it's probably a high amperage circuit; I estimate it has to be 100A or greater. That is not a little ATC style fuse, but rather an ANL or Megafuse or something along those lines. There will probably be a large fuse block near the batteries. Here's an example of what to look for; this is an ANL fuse holder with a 300A fuse I installed for my inverter.

I recommend disconnecting the negative cable from the battery bank before you remove this fuse, because if you don't, then if your ratchet or wrench touches the body of the truck as you're removing it, you'll create a massive short circuit.

Okay, so disconnect the negative from the batteries and tuck out of the way/insulate them.
Find something like this and remove the centerpiece, which is the fuse block and tuck those mega wires out of the way and insulate them, then reconnect the negatives on the batteries and power up with the maintainer...and then wait a number of days to see if the truck's battery light comes on and the ding ding ding shutdown - is this correct?

 

[His Word 1st]

Okay, so disconnect the negative from the batteries and tuck out of the way/insulate them.
Find something like this and remove the centerpiece, which is the fuse block and tuck those mega wires out of the way and insulate them, then reconnect the negatives on the batteries and power up with the maintainer...and then wait a number of days to see if the truck's battery light comes on and the ding ding ding shutdown - is this correct?

And then if all's well and the shutdown issue isn't happening or the batteries seem good, drive the truck to have the batteries and alternator tested and potentially to be repaired if it's too much for me.

If it is the fuse block then I would just need to replace that itself and the power draw would stop, right? Is that costly?

Thank you so much for your time and effort. God bless you!

 

[jdwarren]

Okay, so disconnect the negative from the batteries and tuck out of the way/insulate them.
Find something like this and remove the centerpiece, which is the fuse block and tuck those mega wires out of the way and insulate them, then reconnect the negatives on the batteries and power up with the maintainer...and then wait a number of days to see if the truck's battery light comes on and the ding ding ding shutdown - is this correct?

1) Disconnect the master negative cable from the battery bank; not the interconnections between the (parallel) batteries, but the one that actually goes to the block, starter, etc.

2) Find main power connection for liftgate and disconnect it. The easiest and most preferable way to do this is to find the fuse for that circuit and simply remove it; you can just put it in your glovebox for now. However, there exists a possibility that whoever installed the liftgate did a half-assed job and either put it somewhere inaccessible, not obvious, or just didn't fuse it at all (!!!), in which case you'll have to either disconnect the supply cable itself. Since it's apparently fed from an ignition-switched source, it's anyone's guess where it's tied in. You may have to consult some wiring diagrams for your particular truck and figure out which power posts are ignition-switched and then go look there for anything that looks like an aftermarket connection. Alternatively, you may be able to just disconnect the power supply at the liftgate itself. In that case, you absolutely must insulate and tie off that cable because if it's flopping around it could short circuit against the frame/body of the truck. The downside to this is that if there's a relay or solenoid upstream of the power connection at the liftgate itself, then disconnecting power at the liftgate won't eliminate this potential source of trouble.

3) Reconnect negative cable to battery bank.

4) This may be obvious, but verify that the liftgate does not function after you've disconnected what you believe to be its power supply. Ensure that the liftgate power indicator light does not ever illuminate.

5) Charge up the batteries with your charger.

6) Test truck's operation. Be patient and run it through a long enough duty cycle that you're almost 100% certain the issue is gone, or until the problem reoccurs. If everything is normal, we've isolated the issue to the liftgate. If issues persist, describe them and we'll take it from there.

 

[jdwarren]

And then if all's well and the shutdown issue isn't happening or the batteries seem good, drive the truck to have the batteries and alternator tested and potentially to be repaired if it's too much for me.

If it is the fuse block then I would just need to replace that itself and the power draw would stop, right? Is that costly?

Thank you so much for your time and effort. God bless you!

It's almost certainly not the fuse block itself; a fuse block is literally just a piece of insulating material with two battery terminals run through it. I suspect it's something in the circuitry that switches the power to the liftgate, i.e. a solenoid or relay. But those parts are not expensive either. More than a fuse block but very manageable and probably not difficult to install unless they're in a bad location.

 

[His Word 1st]

 

[His Word 1st]

1) Disconnect the master negative cable from the battery bank; not the interconnections between the (parallel) batteries, but the one that actually goes to the block, starter, etc.

2) Find main power connection for liftgate and disconnect it. The easiest and most preferable way to do this is to find the fuse for that circuit and simply remove it; you can just put it in your glovebox for now. However, there exists a possibility that whoever installed the liftgate did a half-assed job and either put it somewhere inaccessible, not obvious, or just didn't fuse it at all (!!!), in which case you'll have to either disconnect the supply cable itself. Since it's apparently fed from an ignition-switched source, it's anyone's guess where it's tied in. You may have to consult some wiring diagrams for your particular truck and figure out which power posts are ignition-switched and then go look there for anything that looks like an aftermarket connection. Alternatively, you may be able to just disconnect the power supply at the liftgate itself. In that case, you absolutely must insulate and tie off that cable because if it's flopping around it could short circuit against the frame/body of the truck. The downside to this is that if there's a relay or solenoid upstream of the power connection at the liftgate itself, then disconnecting power at the liftgate won't eliminate this potential source of trouble.

3) Reconnect negative cable to battery bank.

4) This may be obvious, but verify that the liftgate does not function after you've disconnected what you believe to be its power supply. Ensure that the liftgate power indicator light does not ever illuminate.

5) Charge up the batteries with your charger.

6) Test truck's operation. Be patient and run it through a long enough duty cycle that you're almost 100% certain the issue is gone, or until the problem reoccurs. If everything is normal, we've isolated the issue to the liftgate. If issues persist, describe them and we'll take it from there.

Thank you for the detailed write-up here - that's very useful for me!

I just uploaded two more pictures of what looks to me like it's wiring from the liftgate to the battery; could that rectangular box be what I'm looking for? I'll take those off and then flip the liftgate switch when the truck's running to see if that's them then. Thanks again!

 

[jdwarren]

Thank you for the detailed write-up here - that's very useful for me!

I just uploaded two more pictures of what looks to me like it's wiring from the liftgate to the battery; could that rectangular box be what I'm looking for? I'll take those off and then flip the liftgate switch when the truck's running to see if that's them then. Thanks again!

Yes, that actually looks like it may be a DC circuit breaker. If so, it takes the place if the fuse and holder. There should be a switch on it that allows you to open (disconnect) that circuit, which has the same effect as removing a fuse. If that's a circuit breaker you can safely open it without disconnecting the negative battery cable like I mentioned in my instructions; just ignore those parts of the procedure.

Edit: If that breaker is what controls power to the liftgate, then it doesn't look like the power supply itself is ignition-switched. Instead, the switch in the cab may be connected to an ignition-switched supply. But let's just take it one step at a time and see what happens. Make sure that after opening that breaker the liftgate doesn't function; if it does, then that's not its power supply.