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2012 Volt heat issues solved!! finally

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Reed Lalier chevrolet in fayetteville, NC: After my 3rd trip to the dealer this winter they solved the heat issue. background:

The car could not provide heat despite maxing it out on the screen. After a control module here, a coolant leak into the cylinder head there, it was latter discovered that there is a filter inside the heater core that is not in any maintenance book or diagram. Its like a ghost part, nobody knew it was there except some master mechanic on some national Chevrolet hotline the dealer called for last resort advice. Sure enough, this cylinder looking filter (think refrigerator filter cartridge) was like "swamp" dirty. Its not a consumable part, it just gets cleaned and put back in. After cleaning/unclogging it, the heat was there.

This is a pre-owned volt for us that we got in the summer and we're experiencing the real heat for the first time.

I hope this helps other Volt owners with heat issues. Ask the dealer to check that filter inside the heater core near the firewall. They might not know it exists because like I said, this thing doesn't appear in any or most maintenance books/diagrams.

200-300 dollar job, but the dealer was nice to us (free) with a loaner. That's what happens when you don't get impatient and you work the survey system respectfully. Feel free to email me at ([email protected]), I would love help other volt owners if it comes to it.
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The previous owner probably got a "coolant flush" at Jiffy Lube. What else would clog up a closed loop in an essentially sealed system?
 

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After a control module here, a coolant leak into the cylinder head there, it was latter discovered that there is a filter inside the heater core that is not in any maintenance book or diagram.




HEATER CORE - 2012 Chevrolet Volt (13406298)


Seems the entire heater core for the Gen1 Volt is avail online for @$50 and is the Lowest Replaceable Unit (doesn't break down any further in the parts diagram)...
 

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I just had the same issue with my 2014 Volt. Intermitent problem, sometime heat, sometime nothing. I brought to the dealer once, when they checked it was working so they said there is no problem. It kept doing it, only cold air coming out (almost like if the AC was on...). They test drove for a while and acknowledged the issue. Each time it failed in their hands, they tried pulling code, but got nothing. So it does not seems to be an issue a sensor can pick up.

Same thing as OP, they had to call the TAC to get advises and were told to change the coolant heater module and bleed/replace the coolant. I wonder if replacing the coolant heater module also involve the filter mentionned here...

Anyway, the heater is working good now.
 

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Looks like that would be fairly easy to access. I don't have heat issues but I think I'll look at my car tonight just to inform myself.

It appears that the heater core actually looks like this. I wonder if the OP is mistaking that for a filter or if there is something else in there somewhere.

Given it's physical location I could see garbage sucked in from the outside (leaves and other debris) collecting on top of that core and restricting airflow.

This page also has a nice diagram breakdown of parts

Also, just for fun.... how to replace your cabin air filter.
 

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This is most certainly related to bad head gasket and/or contamination of the coolant with air or incompatible coolants added.

Because of all the narrow passages everywhere in the system, did they flush the entire coolant system to make sure there isnt other places this stuff is gathering?
 

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Discussion Starter · #13 ·
Barry, that's how it all started. Low coolant level = low/no heat. Why low coolant? where is it going? drips on the ground? no, coolant in the oil? YES! Why coolant in the oil, check compression of cylinder, cylinder 3 had a leak, compression ok, gasket not ok, replaced gasket. Car given back, still no heat, car returned. Head scratching resumes.

Heat control module replaced, car given back...car returned, head scratching resumes....less hair now.

Called hot line, information about heater core filter provided, cleaned filter, replaced coolant, REAL HEAT!!! Hair saved.
 

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Did they list a part number on your receipt.
 

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Looks like that would be fairly easy to access. I don't have heat issues but I think I'll look at my car tonight just to inform myself.

It appears that the heater core actually looks like this. I wonder if the OP is mistaking that for a filter or if there is something else in there somewhere.

Given it's physical location I could see garbage sucked in from the outside (leaves and other debris) collecting on top of that core and restricting airflow.

This page also has a nice diagram breakdown of parts
This actually makes more sense. Perhaps they removed this and cleaned it thoroughly on the outside which allowed air to pass over it and a good pressure cleaning for the inside pushed debris that was lodged inside that then allows fluid to travel through the smaller tubes. With the bad head gasket he had to start with this would make complete sense.

However, he does say it was a cylinder looking filter so perhaps there is an unknown filter there. This would be out of the ordinary as no debris should get in there.
 

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Discussion Starter · #16 ·
2VOLTFAMILY guy:

Allow me to clarify. Cylinder, as in Piston cylinder (Cylinder #3 i believe). It was believed at the time the cylinder of the piston was allowing coolant to drip/flow into the cylinder and mixing with the oil. They removed it, took it to a machine shop for a pressure check, that was fine and replaced the gasket. Then they moved on to the heat control module or something. My wife got the car back, the heat turned off again. We took the car back, and that is where they learned about this filter in the heat core. Its not a seperate part so it just gets removed and cleaned and reinstalled...at least that's what they did for mine.

The dealer didn't see an issue until they actually let the car sit with the heat on...and waited for it to turn cold again. The other visits they just turned the heat on...felt some heat and called it a day. After the 3rd visit, I'm sure they were more eager to get this car fixed, not to mention I got the general manager involved (respectfully via a survey).
 

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Perhaps they didn't bleed the system and are merely covering their tracks? I smell BS here. SInce when would a dealer mechanic remove a heater core remove the filter and then replace the original core. Standard practice would be to replace the entire heateater core.
 

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Reed Lalier chevrolet in fayetteville, NC: After my 3rd trip to the dealer this winter they solved the heat issue. background:

The car could not provide heat despite maxing it out on the screen. After a control module here, a coolant leak into the cylinder head there, it was latter discovered that there is a filter inside the heater core that is not in any maintenance book or diagram. Its like a ghost part, nobody knew it was there except some master mechanic on some national Chevrolet hotline the dealer called for last resort advice. Sure enough, this cylinder looking filter (think refrigerator filter cartridge) was like "swamp" dirty. Its not a consumable part, it just gets cleaned and put back in. After cleaning/unclogging it, the heat was there.

This is a pre-owned volt for us that we got in the summer and we're experiencing the real heat for the first time.

I hope this helps other Volt owners with heat issues. Ask the dealer to check that filter inside the heater core near the firewall. They might not know it exists because like I said, this thing doesn't appear in any or most maintenance books/diagrams.

200-300 dollar job, but the dealer was nice to us (free) with a loaner. That's what happens when you don't get impatient and you work the survey system respectfully. Feel free to email me at ([email protected]), I would love help other volt owners if it comes to it.
FYI this filter is not "in the heater core" itself. It is technically in the hose between the heater core outlet and the 3-port valve inlet. If you trace that line just in behind the engine next to the bulkhead you will find a pair of hose clamps in the middle of the hose that once removed allow the removal of the filter.
The filter designed to prevent foreign debris from entering the valve and pump in the event of a contamination, is not considered to have any scheduled maintenance.

However when properly following the diagnosis of a low/no heat condition (with no DTCs) the "Heating Performance" diagnostic chart specifically directs the technician to check this filter. The presence of this filter is also covered in the Volt technician training.
So they simply missed it somehow...
WOT
 

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Discussion Starter · #19 ·
Subdewd: Thanks for the insight, I wouldn't think too deep about it. We are all human after all. I wasn't charged for this last bit of service to the heatercore/filter in the tube thing. Its possible they just decided to clean it instead of spending 50 dollars to charge me...they were already eating cost, so I won't complain.

WOT: Good info indeed! Its very possible the tech at the dealer (he's the only Volt/Corvette tech) missed it. But like anything else, this is a practice, and when you don't have a lot of volts coming in to work on...you're not going to know everything. I say to coach myself into staying patient. Trust me...I owned a 2009 mercedes C350 and that thing was ROCK SOLID, never an issue. So, if this didn't fix it, yeah, the VOLT would have been on the chopping block with less than 12 months of ownership.

I will say I do enjoy the evolving technology in plug in hybrids and learning the complexity of these vehicles. That's part of my staying power with this car...the chance to learn and see these vehicles improve each time one comes out.

Keep the posts coming!!

-David
 

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FYI this filter is not "in the heater core" itself. It is technically in the hose between the heater core outlet and the 3-port valve inlet. If you trace that line just in behind the engine next to the bulkhead you will find a pair of hose clamps in the middle of the hose that once removed allow the removal of the filter.
The filter designed to prevent foreign debris from entering the valve and pump in the event of a contamination, is not considered to have any scheduled maintenance.

However when properly following the diagnosis of a low/no heat condition (with no DTCs) the "Heating Performance" diagnostic chart specifically directs the technician to check this filter. The presence of this filter is also covered in the Volt technician training.
So they simply missed it somehow...
WOT
Thanks for this info WOT. My 2013 Volt is experiencing this problem. Rick Hendrick Chevy here in Duluth GA has a handful of experienced Volt technicians whom I think will be able to accurrately diagnose & fix it, but I still like to be involved to help prevent mistakes if I can (i.e., if they come to me with request to do something more than check the filter, I will know to ask if this inspection has already been done). Hopefully it will only be the filter, and that is all that gets touched.
 
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