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Heat Only Works When Going Fast
jipioneer07
post Jan 17 2018, 08:25 PM
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So my Tahoe is running great, engine heats up normally and stays around operating temps, but the AC will only blow hot air when the car is going above 55. Other than that it blows cold air. Actuators were replaced a few months ago.


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carguru
post Jan 17 2018, 08:38 PM
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So, once the temp gauge registers temp above 160 degree, what is the temperature of the hvac box on the passenger side? How long between time you start up to the time you get to highway speed?


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jipioneer07
post Jan 18 2018, 07:47 AM
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QUOTE (carguru @ Jan 17 2018, 09:38 PM) *
So, once the temp gauge registers temp above 160 degree, what is the temperature of the hvac box on the passenger side? How long between time you start up to the time you get to highway speed?

Temp gauge registers above 160 in less than a minute, takes about ~10 minutes to get to highway speeds. Not sure what you mean by temp. of HVAC box, but both passenger and driver side climate control are typically turned all the way to 90 in the morning.


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carguru
post Jan 18 2018, 08:40 AM
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Once you reach temperature, stop feel whether the air box on the passenger side is warm or cold. This will diagnose whether coolant is flowing to the heater core or not. Something doesn’t sound right with it reaching 160 that quickly. From memory, gassers take about 5 minutes or so for the coolant to warm up (around 10 for the diesels) when it is really cold out.


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jipioneer07
post Jan 19 2018, 08:11 AM
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Ill take a look on the way home. Ill time how long it takes to reach temperature too.

EDIT: My first thought was something to do with coolant, but since the engine isn't overheating and hovers around 210 I figured that couldn't be it.

This post has been edited by jipioneer07: Jan 19 2018, 08:12 AM


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carguru
post Jan 19 2018, 02:12 PM
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Have you flushed your coolant at all? My thought is that either you have blockage to your heater core or your thermostat is acting up and not heating the coolant as quickly as you think it is happening.


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jipioneer07
post Jan 23 2018, 01:08 PM
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I was wrong, it takes ~5 minutes of idling for the engine to reach temperature. Now that its been a little warmer the heat hasn't been a problem. I'll have my coolant flushed this week when I get an oil change and see if that fixes it.


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kidphc
post Jan 25 2018, 08:02 AM
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QUOTE (jipioneer07 @ Jan 23 2018, 02:08 PM) *
I was wrong, it takes ~5 minutes of idling for the engine to reach temperature. Now that its been a little warmer the heat hasn't been a problem. I'll have my coolant flushed this week when I get an oil change and see if that fixes it.


Try getting the heater core flushed. If you been mixing colors of antifreeze then can create a jello clogging the heater core. Do you get heat from the back unit all the time or is it intermittent. It is usually or the other that is clogging.

Generally, if you only get heat when the rpms are over 2000, it is because the heater core is getting clogged and the increased rpms are allowing enough flow of coolant to get past the blockage. Sometimes its just a tired water pump.
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