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Heater not working

Tiny
CHERYL21
  • MEMBER
  • 2015 GMC TERRAIN
  • 4WD
  • AUTOMATIC
  • 100,125 MILES
Heard a noise like a door slamming enroute to work. Drive home had no heat. Got a mechanic to look at it, said it was the thermostat, said he changed it, sent me to valvoline to flush the coolant did that still no heat. Second mechanic decided it was bigger than he could handle told me to take it to a dealer. Brought it to Quirk GMC they found no leaks or air in system, heater core flowing normal, temperature actuator moving removed that to find HVAC temperature door broken, replaced that said was working. Picked up truck on 2/5 took forever to warm up but was toasty warm on ride home. Went out today was lukewarm at best and noticed fan was running constantly. Went out to clean snow off truck 4 hours later left it running for 15-20 minutes no heat or defroster I have spent $2,240.22 and I still have no heat. All I want is someone to tell me what I have to do to fix this darn truck because I don’t understand why after all this it’s still not working!
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Sunday, February 7th, 2021 AT 5:15 PM

7 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
When you say the fan was running continuously, do you mean the blower motor or the engine cooling fan was running?

Here is a video that will take us through this issue but I think the last shop at least touched the issue. The fact that is wasn't working, then it was after they fixed the door, then it went to kind of working to not working. That tells us this is something to do with the blend door.

https://youtu.be/SNRb6pSwYuU

https://youtu.be/Eqf-H3COtSo

Below you will find the process on how to replace the actuator which is what I suspect this is. However that may change when we find more out about the fan. Thanks
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Monday, February 8th, 2021 AT 7:36 PM
Tiny
CHERYL21
  • MEMBER
  • 4 POSTS
So before I heard from you I left my truck with another mechanic just to see if he could figure out why my heat wasn’t working, so he told me he had to jump start it which I haven’t had to at all and asked if the fan was always running told him yes and he said it was the coolant fan also on the drive home my engine light was on which it wasn’t before, I have a short drive home which is about 12 minutes so I keep the fan off but try it every now and then to see if it works. Driving home with it off today I noticed that I got warm air from one of the vents about a minute from home but when I put the fan back on it blew cold air. I hope this additional info helps you cause I am at a loss as what to do and I don’t even know if I should still be driving this as it is.
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Tuesday, February 9th, 2021 AT 11:33 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
So I am thinking we have a couple issues. If the battery was drained and the coolant fan was running, that is the fan out under the hood behind the radiator. Is that the one that he was looking at?

The fan inside the vehicle is called the blower motor so if you have no heat, let's get the engine hot and then grab both heater hoses going in through the firewall. They should be hot. If they are not then we have a coolant flow issue.

Let us know and we can go from there.
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Tuesday, February 9th, 2021 AT 6:33 PM
Tiny
CHERYL21
  • MEMBER
  • 4 POSTS
So it is the fan under the hood and I had someone touch both hoses, the one on the left was hot the one on the right was cold, he said he could feel air in that hose, he took the cover off the coolant and we could see it bubbling as he squeezed the hose. Now I don’t know if that is the only reason I don’t have heat because now my battery is dead, so I have another issue to take care of. Also this kid went to his shop and got some gadget that gives codes he said and when he checked he said I had a p0128 he didn’t know if it was recent or if it wasn’t reset so he left it as is. Hope this info helps.
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Wednesday, February 10th, 2021 AT 5:44 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay. We are making progress. We need to start with eliminating a possible head gasket or other leak.

Let's start with these two guides. First is a head gasket test.

https://www.2carpros.com/articles/head-gasket-blown-test

Next is a cooling system pressure test.

https://www.2carpros.com/articles/radiator-pressure-test

The fact that your cooling hose coming from the heater core is cold indicates a restriction or low on coolant. However, this is the source of the no heat and explains why it is there sometimes and others it is not.

As for the code that you have, is for the engine cooling system signal performance issue. That is not going to cause our issues and could be a result. So we need to start with these two things first and then go from there.

Thanks
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Wednesday, February 10th, 2021 AT 7:15 PM
Tiny
CHERYL21
  • MEMBER
  • 4 POSTS
Just wanted to give you an update and thank you for your help. So we brought it back to GMC and they hooked it up to their machine and got the error code for the thermostat, in replacing it they found that the first person put it in backward and it was stuck open hence no heat. So they gave me a new one and I am happy to say I now have heat! Thank you for doing all that you could to help me with my problem as I had no idea what was going on.
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Wednesday, February 17th, 2021 AT 3:44 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
That is great info and totally makes sense now that we know that is what happened. Unfortunately those are always the hardest to figure out because you assume they would not make that mistake but it is great they found it and took care of it for you.

Thanks for the update. Please come back to 2CarPros next time you need some help.
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Thursday, February 18th, 2021 AT 4:37 PM

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