Heater blows cold
 

Hey, new here :-)

My heater is blowing cold for most of the time with a period of here or there that it will get hot and may go back to cold and stay cold. Coolant level is full and temp stays normal. Before I start throwing parts at it as a guessing game, has anyone experienced this with their car?
Thanks!

Welcome to the site, yes, it was the thermostat, if you have not changed it or the coolant, time to do just that!
We highly recommend using Dexcool in a 50/50 mix with distilled water!
And get the correct AC Delco thermostat, other brands don't seem to open in the time frame the computer is looking for, this causes the CEL to come on and the code P0128.

Read this handy how to!


https://www.chevyhhr.net/forums/how-...l-p0128-24493/

http://www.jcwhitney.com/p3042205/sku-3503285.jcwx

Welcome to the site. :thumb:

It helps us help you if you give the cars info like year, model, mileage, how long you've owned it, etc.

You stated "temp stays normal". If you mean by the gauge on the dash, they're not real accurate. Turn to the digital coolant temp reading in the car's info center and check it there. Below 180 degrees after warm up usually will point to a bad thermostat.

Most likely it's the thermostat as Oldblue said. Start with that 1st. If that's not it you may have a blend door problem under the dash. ( a kind of rare issue)
Blend door is way more complicated to fix.

Did you not have a check engine light?

By coolant temp do you mean the digital read out or the analog.

If no check engine light and the digital temp is around 180F, I think you probably have either an air bubble or a clog in the heater core.

The digital temp sits about 180 and ya no check engine light

Howdy!
It's an 08 SS with 85,000, original owner.......yea I think the thermostat might be a good start. I'll double check again what the digital temp is sitting at.

180 F would be a little low compared to what other SS owners see. Mine usually stays around 185 to 190 while moving. Can get a little hotter while sitting at a red light.

Many HHR owners have experienced thermostat problems. Both in the regular and SS models.
The original thermostat design wasn't very good for the long term. They can fail because the rubber O-ring deteriorates and dislodges from the center of the stat.

P.S. If you're the original owner and have never changed the Dexcool, you're overdue. Now is a good time for a thermostat and coolant change.

Agreed, I never see 180 after warmup. That being said, even at 180, the heater shouldn't blow cold air.

Thank you! Yea I've never changed the dexcool, I know the stuff is crap😳 I'll start there.....

I trust you mean your DexCool is worn out, since it is more than 5 years old. Not that you think DexCool is a bad product.

Correct 👍🏼 I'm aware that it should have already been changed lol

A stuck open thermostat! Cold air will blow from the vents!

What am I missing? How can it blow cold air if the coolant is at 180*?

The may not necessarily mean "cold" they might mean "not hot" if that makes sense. On my LT when the temp just barely turns over to 180 it isn't quite as hot as it is when the temp gets to 190. At 180 the thermostat is designed to start to gradually open, thus the heat may be different through the vents until the engine and coolant system reach true operating temp. Just my 2 cents LOL. Also, even for an LT I think running down the road after a good ways at only 180 is too low. On nice stretches of highway my temp sometimes can get down to 183 but thats about it. I dont thing the computer will trip a code until the temp drops to 176 or below for a certain period of time.

Thermostat is open the coolant won't get hot as it constantly circulates, it's not in the block long enough to rise to temperature. Now this should trip a code, P0128, but I have seen HHR's with this issue and not set the code.
I've changed the thermostat and flushed and filled the Dexcool and then there was heat.
I don't know the physics of it I just know the results of it! http://sd.keepcalm-o-matic.co.uk/i/d...-physicist.png

You can use some air to check for obstructed heater core while the t-stat is out.

Ok so here is the latest.....left home, hopped on the freeway. The heater was already warm at 180. It was warm until half way to work and it just flat lined and was like warm. At that time, it was sitting anywhere between 190 to 200 still blowing luck warm. I'm assuming the thermostat is stuck open.

And or there is air in the heater core, but because of age , replace the thermostat and the Dexcool.
Park the SS nose up a sloop like a driveway or jack up the right front corner to allow the air to escape, put the heater in full heat while your refilling the rad.

Well, when you're at 180 or above, it's supposed to be open. Being 'stuck open' should only be a problem for getting to operating temp(and would set the P0128 code). Once you reach operating temp, it's supposed to be open. That's why I don't think it's the cause of your heater not working properly.

I would be looking for a clogged heater core(like donbrew suggested) or a blend door problem(like firemangeorge suggested).

But sure, you're probably due to replace the thermostat and the DexCool, and like donbrew said, blow out the heater core while you have the thermostat out.

IF it turns into a blend door actuator issue, here is a link to the procedure. Thanks to former mod ChevyMgr.
Post #11 in this link: https://www.chevyhhr.net/forums/prob...m-33767/page2/

My bet is on an air bubble. Just been through this, but I could get heat if I did some hard pulls. 5MT SS here.

Ok guys! I replaced the t-stat and coolant last Saturday, a week ago. Everything went smoothly. Just yesterday it started doing the same exact thing. It went a whole week nice and hot. I was on my way home from work last night, started hot and then again went lukewarm. Now I notice once it goes lukewarm, it tends to blow more air out of the vents, then once it goes back to hot, it slows down a bit, like it has a fluctuation in a door or something. My mind is boggled. What I don't get is, why it went a whole week without an issue. I would think the issue would still be daily as it was before i changed the t-stat. I did noticed that the seal in the t-stat didn't look good, so I thougt I nailed it.

Did you burp the system real good? Sometimes those air pockets can be real stubborn. Other than that, you're back to a blend door problem.

Dammit, lol! Yes I did burp it well. It was an SOB!! Is it one particular blend door?

Check the link in post #20.

Did you check the heater core like donbrew suggested?And here's the link for the blend door again.

Yes, blew air through it

Did you use a AC Delco thermostat ? Dexcool ?
What are your temps running now ? Are the temps the same when it was working correctly and then started acting up again this time ?

There's pictures in post #2 here...

https://www.chevyhhr.net/forums/prob...ctuator-51029/

Yup, delco t-stat and dexcool. The temp currently is running between 183 - 198. I believe the temps before were in the 190's to 200

Any chance you are using defrost or recirc when you are experiencing cold air?

To be honest, it happens regardless if defrost and recirc are off or
on. I tried it each way to eliminate if it would only act up one way but it's the same. When I have the blower on, like say setting 2 and it's blowing lukewarm air, it blows more as if more air is coming through then when it's blowing hot. When it turns too hot, I feel the level of air kick down a bit. Just an observation......

I just read through the blend door thread. It seems there is a calibration involved. It may need to self calibrate every time the battery is disconnected. You could try disconnecting and let it try to self calibrate again. It may turn out that you have a bad HVAC head unit, but we're not there yet.

The reason I asked was because either of those things turns the A/C on without any indicator light.

Ok, I'll give that a shot. Yea, I don't want to throw more stuff then I have to at it until we have ideas.

SOUNDS LIKE A BLEND DOOR MALFUNCTION AT RANDOM MOMENTS. Had same problem with ours and guess who fixed it....."Chevymgr" at Reliable Chevrolet in Richardson Texas.

Is the blend door reasonably priced? I'll throw one in it......

well the part number from our common parts thread is 52411441, which doesn't turn up much on google, one used part on eBay 52411441 08 2008 CHEVROLET HHR HEATER BLEND DOOR ACTUATOR MOTOR #C-48 | eBay

The number turns up no results on wholesalegmpartsonline.

It's a little difficult to tell, but looking at the exploded diagram, and the orientation of the heater core lines, it looks like this is the part number 10393075.

ACTUATOR. AIR CONDITIONING (A/C) Control. A/C & HEATER MODULE ASM; HEATER for Chevrolet HHR (2005 - 2011). #10393075

Looks like there is a Dorman part number, 604-133

Ok! So I just drove to the store, ran the heater and is working as should lol. Definitely intermittent. Cycled all the settings, cycled fresh to recirc, all blows hot.

Well, keep us posted, hopefully it was just one last air pocket that worked itself out!