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I am th8nking my car has either a clogged filter or a bad pump.. heat does not work in ev mode and can actually blow cold air even if the ice engine is still warm but not when it’s running why I am thinking a pump...... also the ev heater icon under climate turns itself off like it thinks the coolant is up to temp when it is not..

Anyone with any suggestions I would appreciate it just trying to research now to find the answer

So there is a new and better k10 unit that would be worth getting from a junkyard if possible and putting in?

Also does anyone know if the system has to be in vacuum to change coolant was th8nking of doing that at same time as the pump I assum I am about to change but am still searching the thread to figure out if I am correct about it being auxiliary. Pump or no this thread has me leaning that way so far.

Any advice or experiences that might apply would be appreciated.

TIA,
Anthony
 

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Also heat seems intermitent in ice running mode does that mean the 3way valve is either bad or needs programmed?
I’m having the same problem with our 2014 Volt. I believe it’s the pump - (GM Part# 13597899). No heat at all in EV mode. Good heat when ICE is running. Although the ICE does shut off intermittently even when in hold mode. When the ICE shuts off, then the heat diminishes - as you said “intermittent”) (I’m not sure if the 2-way valve (not 3-way) switches back to EV mode any time ICE shuts off? Probably does which causes a fairly fast cool off because the pump is not circulating any fluid when in EV mode.
 

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I am th8nking my car has either a clogged filter or a bad pump.. heat does not work in ev mode and can actually blow cold air even if the ice engine is still warm but not when it’s running why I am thinking a pump...... also the ev heater icon under climate turns itself off like it thinks the coolant is up to temp when it is not..

Anyone with any suggestions I would appreciate it just trying to research now to find the answer

So there is a new and better k10 unit that would be worth getting from a junkyard if possible and putting in?

Also does anyone know if the system has to be in vacuum to change coolant was th8nking of doing that at same time as the pump I assum I am about to change but am still searching the thread to figure out if I am correct about it being auxiliary. Pump or no this thread has me leaning that way so far.

Any advice or experiences that might apply would be appreciated.

TIA,
Anthony
You can remove the pump and let coolant drain out and it will be fine.

To replace the K10 module the intake manifold needs to be pulled off the ICE, just a heads up.
 

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Add me to the "no heat in EV mode" list. Mine is a 2014 Volt with 46,000 miles. Absolutely no hint of heat until engine is run (either by placing in Hold mode or popping open hood). Even then, when the engine was first started, there was no heat for several minutes of engine warm up (which makes senses) but then there was a bunch of clunking under the dash (vent doors changing position maybe?) followed by good heat. Based on what I can gather from this thread, that would suggest an issue with: K10 heater, 3-way valve, a fuse, or the electric auxiliary circulation pump, or the vent doors in the HVAC system, right?). But here comes the strange thing: after driving around in the Hold mode to get heat, I brought it to a stop and it went back into the EV mode, and I continued to have heat. Heat continued, while stopped, when I put it back into the Normal mode. But during all that time (in either mode), there was a loud humming sound from the passenger side wheel well. As long as that humming continued, the heat would work in the EV mode. Can anyone confirm what that noise is, and what it means in terms of my diagnosis?

Then, to make things even more strange, I turned off the car, which stopped the humming. I then turned it on again, still in EV mode, and the sound did not return, but the heat was now fine -- while in the EV mode. So, something is intermittent. It's as if I exercised it and it started working again. But I'm sure it will fail again - it's followed this pattern a couple times. The dealer couldn't find the problem, because the heat worked okay for them on the day we took it in. Any suggestions on what to do would be appreciated.
 

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I plan to replace the heat circulation pump and was wondering if others disconnected the 12 V battery when they made this repair. I didn’t see that mentioned in any procedures. Thanks
 

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Discussion Starter #67
Greetings all,

As the OP on this thread, I want to report the status as of two years on. Good news, the heater problem has stayed solved and there has been no reoccurrence. To refresh you, all I needed to do was to pull the fuse as shown on Somm's diagram. Apparently, this reset software and solved the problem.

Hoping your solutions have worked for you, too.
 

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there was a loud humming sound from the passenger side wheel well. As long as that humming continued, the heat would work in the EV mode. Can anyone confirm what that noise is, and what it means in terms of my diagnosis?
The humming is most likely the coolant circulation pump. It's mounted inside the passenger wheel well. Easy to get to and replace if that's found to be the culprit.
 

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Took my 2014 in today for intermittent heater issues.... most of the time would not heat in electric mode but worked fine when engine was running in Hold... Dealer informed me that diagnosis would be $98. Two hours later found DTC B101D on Coolant Heater Control Module - module shorted internally. When they told me they stated that the module was $1300 plus labor charges.
I whipped out my GMPP which they said was not on my file but I did purchase from them a year after I purchased car. After checking out 45 min later They said all was covered and module was ordered. I elected to return on 12/30 so they should have part for sure by then. Glad purchased it as it cost less than this issue ..... and I have 5 more months on it or 24 K miles to go under warranty.
 

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I replaced the Aux Heater Circulation Pump located behind the front wheel well - and my EV heat is now great!!
 

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Somewhat of same condition for my 2014 ..... took into dealer and described that heat would almost always work when engine was running but rarely when in electric mode. Dealer tested systems and found a DTC on the heater control module which they had to order. I returned back 2 weeks later for the fix and they also replaced the heater element and had to open up the coolant system to do so. I was informed when diagnosed that the repair was not covered under warranty. Luckily I had purchased a GMPP extended warranty that covered the fix .... So far system is working great ...heat is much faster than I remember it being .... no blasts of cold air from fan .... it ramps up when heat is warm and ramps down as temp setting is matched . Hats off to techs at Shelor Chevy in Christiansburg ,VA.
 

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I had similar situation with heat on MY 2014. Scheduled appointment and dealer up front stated that diagnostics would be $95 and no warranty for heater repairs. What was found was DTC on the heater control module that a service bulletin referenced and required replacement of module to fix based on date code on module. I advised them that I had purchased a GMPP warranty within first year of ownership. When I returned for module, the heater element was replaced which required opening the coolant loop.
The heat works great now , I think better than ever , and the GMPP covered everything. The cost of the repairs was considerable more that the $0 deductible warranty cost. The salesman that sold me the warranty advised me to purchase if I planned to keep the vehicle and to purchase GMPP due to unique parts on the vehicle that most warranty would not cover .
 
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