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Heater Blowing Cool air.

Heater Blowing Cool air.

Postby Galen [OP] » Oct 15 2012, 1:37pm

I have a 2001 Silverado 1500 with the 4.8L engine. The AC works fine but the heater only blows cool air. We just replaced the thermostat and it still doesn't work right. In the process of replacing the T-stat we flushed the whole system but not the heater core directly. You can get luke warm air on say the vent setting but if you move the knob to another setting and then back to the vent we seem to loose what little warmth we get. My next steps are to add some radioator flush and possibly flush the heater itself. Any ideas what could be causing this?

THanks

Galen
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Re: Heater Blowing Cool air.

Postby ASTE25 » Oct 15 2012, 8:13pm

It sounds like you may have a problem with the blend door actuator and not the actual heater core (since you state you do get heat at times). Do a search on this forum or Google to see how to test and replace it.
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Re: Heater Blowing Cool air.

Postby red16 » Oct 16 2012, 11:42am

I had the same problem.It was an air lock in the heater core.It needed to be "burped".You can try overfilling the reservoir,sometimes it will fill.Make sure both of your heater hoses are the same temp.If 1 is warmer than the other,it is not flowing thru the heater core.
In my case,it was not flowing thru the heater core.Unhooked one hose,and was going to flush the core.When I turned the water on,it went gurgle,gurgle,gasp,gasp,and spit a couple times,and flowed freely.It was airlocked.
Filled it to proper level,and it was hot air,just like that.
poor baby just needed burping.
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Re: Heater Blowing Cool air.

Postby Galen [OP] » Oct 16 2012, 5:32pm

We drained the system and flushed it when we replaced the Tstat. Then refilled the system as the Haynes manual said to. Do you think there would still be air in the system?

Thanks again.
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Re: Heater Blowing Cool air.

Postby red16 » Oct 16 2012, 11:11pm

It is quite possible. common problem,after draining system.The heater core is almost the highest point in the system,thus the problem.Look at it,you will see.Like I said,check both hoses,should be the same temp,and feel full.If they are not the same,flush the core.if it gurgles,it was air locked.Have seen it a few times.
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Re: Heater Blowing Cool air.

Postby Machster69 » Oct 16 2012, 11:17pm

Galen wrote:We drained the system and flushed it when we replaced the Tstat. Then refilled the system as the Haynes manual said to. Do you think there would still be air in the system?

Thanks again.

You saying this makes it even more likely air is trapped in the core... easy fix... pop the "quick connects" and flush it from that high point...
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Re: Heater Blowing Cool air.

Postby Galen [OP] » Oct 17 2012, 11:07pm

Update:

I back flushed the heater core and it appears to have fixed the problem. I will know a little more in the morning when it is colder out.

Thanks for the help.
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Re: Heater Blowing Cool air.

Postby Machster69 » Oct 18 2012, 12:56am

WOOT WOOTT!
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Re: Heater Blowing Cool air.

Postby MrMega » Nov 02 2012, 1:35am

Had same problem and just needed "burped". Had noticed last year that the heater seemed a little less 'hot' than the year before... but, last year was barely a winter and didn't think much of it. This year, nothing except maybe 5 seconds maximum of barely heat then dead cold.
Flushed/Back flushed the core in both directions (flow, sputter, flow, sputter - sort of like when water has been turned off in the house, getting out bits of air), then hooked one hose back up and ran water through remain hose that was off until water came out core, then quickly hooked hose on so as little air as possible would be able to get back into the system.
It is blowing SUPER hot air now (hotter on mid setting than on full blast last year).
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