Ď05 Tahoe Heater Acting Funny - Chevy and GMC Duramax Diesel Forum
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post #1 of 10 (permalink) Old 04-05-2018, 08:49 PM Thread Starter
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Ď05 Tahoe Heater Acting Funny

The heater in my wifeís Tahoe has started acting up the last few days and it has me baffled. When I start it up in the morning to let the engine warm, the heater will blow warm air. After getting out on the highway, the dang thing starts blowing cold air. I took it out for a spin this evening in 70 degree weather and it did the same thing. The heater core isnít plugged because both the feed and return lines going through the firewall are hot. The engine gets to operating temperature so I know the thermostat is working correctly. The coolant level is fine. Iím stumped at this point. Could it be the blend door actuator?


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post #2 of 10 (permalink) Old 04-05-2018, 09:51 PM
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Most likely, my Sierra does that from time to time as well. There is a reset procedure to fix it but itís a hit or miss on it actually working.
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post #3 of 10 (permalink) Old 04-06-2018, 05:04 AM Thread Starter
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Thank you, sir. Iíll give it a try.


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post #4 of 10 (permalink) Old 04-25-2018, 10:08 PM
 
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Hate to say it but head gaskets. Check the resivor tank in the morning before u start it. If there is still pressure itís definitely head gaskets.
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post #5 of 10 (permalink) Old 04-26-2018, 07:23 AM
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Originally Posted by Dieselcessna65 View Post
Hate to say it but head gaskets. Check the resivor tank in the morning before u start it. If there is still pressure itís definitely head gaskets.
What makes you think this problem is due to a blown head gasket? How would that explain the HVAC temperature dropping? With a blown head gasket the engine will consume coolant, and he said his coolant level is fine.

I had a similar problem with a 2002 Grand Cherokee, which was known to have issues with the blend doors. That sounds like the most likely explanation to me. Although I'm not sure this is good news as compared to a blown head gasket -- the repair costs can be exorbitant due to the amount of crap that has to come out of the vehicle to access the doors. I heard of repair costs for this problem with my Jeep getting damn near $2,000.

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post #6 of 10 (permalink) Old 04-26-2018, 08:16 AM Thread Starter
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Thanks for all the replies guys. Iím pretty sure itís the blend door actuator because the rear will still blow warm when the front gets cool. Itís pretty intermittent too. It hasnít done it in about 2 weeks.


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post #7 of 10 (permalink) Old 04-26-2018, 08:47 AM
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Does sound like the Blend Door Actuator- that is the one over the trans hump, and the easiest to replace.

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post #8 of 10 (permalink) Old 04-26-2018, 01:49 PM Thread Starter
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Does sound like the Blend Door Actuator- that is the one over the trans hump, and the easiest to replace.


Thatís good to hear. Thank you, sir.


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post #9 of 10 (permalink) Old 04-26-2018, 02:07 PM
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Low on coolant, air pocket, or head gasket can cause the same symptoms. What does the temp gauge read when it does this?

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post #10 of 10 (permalink) Old 04-26-2018, 07:39 PM Thread Starter
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Low on coolant, air pocket, or head gasket can cause the same symptoms. What does the temp gauge read when it does this?


Itís done it at operating temp on down to just warm enough to heat the air. No rhyme or reason as far as that goes. Iím fairly certain itís the actuator at this point since the rear stays warm when the front cools.


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