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Discussion Starter · #1 ·
The heat in my 2012 went out Sunday night while on a long drive. The i.c.e was running at the time when the heat went out. Monday morning after charging overnight there was no heat in ev mode either. I tried all sorts of button cycling combinations on the climate control screen(changed temp, changed in and out of auto climate, defrost, changed vents, etc) and nothing worked.
The heat icon in the climate control screen would briefly change to "on" then will go to "off" and not come back on at all. AC icon would show "on" as usual.

I jumped online and saw a few threads here and a video about cleaning out the filter in the hose coming from the 2-way valve going to the core.

I cleaned the filter screen today and it was NOT very dirty at all...just a bit of black gunk but I'd say filter was 90+% open to flow.

After reattaching everything I still did not have heat in either mode...at first...now for the twist...

With the hood up and i.c.e running I started cycling through the climate control buttons again and after several try's at selecting different modes, temps, etc. I heard a few fairly loud thumps/pops coming from inside the dash behind the climate control screen area. It sounded like a stuck door or flap trying to move(sorta like plastic gears popping). After the loud pops I now have heat with the i.c.e. running but still no heat in ev mode.

I'm not certain if the popping sounds came from inside the cabin or perhaps something attached to the engine bay side of the firewall...perhaps the 2-way valve.??. I'm thinking that maybe the 2-way valve got freed up enough to work briefly after me messing with it when I was cleaning the filter screen.?.?

I went ahead and ordered a new valve this afternoon as it's the next cheapest part to replace anyway and now that I'm familiar with the procedure it will be a relatively easy replacement.

Do you guys think I'm on the right track? Could the thumps/pops be coming from another part of the HVAC system in the dash behind the screen area? The pops were definitely coming from the center area inside the dash/on the firewall.

Thanks in advance for any help and suggestions,
Ken
 

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I am no expert on HVAC but I know a lot about red herrings, dead ends and leads that go nowhere. I have learned that correlation is often not causation. I suppose you would agree.

I used to hear popping/clicking inside my dash. It didn't seem to affect anything. It does not do it anymore. It sounded like a damper actuator clicking.
 

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Discussion Starter · #3 ·
Cloudnine, you certainly could be right about the valve being a dead end. If replacing the valve doesn't fix the issue it's not a total waste of time and money in my book as I'm still replacing a 10+ year old GM electrical component ...I kinda look at it as preventative maintenance. 😋

I have had the blend door/damper actuator sounds also...this new sound came from a similar location deep in the dash but it sounds much louder and sounds like plastic gears popping or skipping teeth while trying to move.

If the new valve doesn't work I'll look at the coolant pump behind the passenger front wheel well.
 

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I hope that it isn't this:
Scroll down to post 18 to see the carnage.
Yours does have a twist in that you now have heat with ICE, even if not battery mode, so your coolant flow valving is still suspect. It's the popping gear / flap open close noise behind the center display that has me worried for you.
 

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Discussion Starter · #5 ·
I hope that it isn't this:
Scroll down to post 18 to see the carnage.
Yours does have a twist in that you now have heat with ICE, even if not battery mode, so your coolant flow valving is still suspect. It's the popping gear / flap open close noise behind the center display that has me worried for you.
I hope that's not it also. I have always had full air flow and the air moves quickly to the desired vents when changing between defroster, dash vents, and floor vents.
I'm hopeful the sound I'm hearing is the stuck valve trying to move...it's mounted center-left/driver side on the firewall and any noises it makes would likely seem to be coming from behind the interior center stack...again hopefully.
 

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If electric heat cycles on then quickly off your aux coolant pump is probably stuck. Immersion heater has a thermostat that quickly turns it off if there is not enough coolant flow and temps get too high.
 

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Discussion Starter · #7 ·
If electric heat cycles on then quickly off your aux coolant pump is probably stuck. Immersion heater has a thermostat that quickly turns it off if there is not enough coolant flow and temps get too high.
Yep...the heat icon will switch to "on" briefly then goes back to "off".
The pump will definitely be the next step if the valve doesn't fix it. I had actually ordered the pump first thing after doing some initial investigating online. Then I came across the posts/video on the forums about cleaning the filter screen if you have zero heat in either mode. Since that was my exact problem, I canceled the pump order so I could try cleaning the screen first before spending any money on parts. So when the engine heat started working after I had been working on and around the valve while cleaning filter screen...I ordered a new valve thinking it could be on the way out. At any rate...the valve is a good bit cheaper than the pump and it seems like a good first shot with the ole' parts cannon. Now that I can use "mountain" mode and get engine heat...I'm not as desperate for heat as I was and waiting a week or so for additional parts is not so bad.
 
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