Heat gauge and AC not working all of a sudden
 

Driving home today and the AC just stopped blowing cold, and the heat gauge dropped and reads nothing. The DIC temp reading is just dashes. Car runs fine otherwise. The HVAC blower works, so does the panel selector. The AC light lights up on the panel, the clutch doesn't seem to be activating thou, and of course, no cold air. It's supposed to be in the high 90's this weekend ....really want to fix this LOL

Checked the diode AC clutch fuse under the hood, its a funny looking black fuse located in the #9 position (at least I think its a fuse), and my OHM reader reads nothing on it, so I'm thinking this is the issue

Anyone else have any feedback. Its a holiday here today (Canada Day), so I can't just run out to NAPA and see if they have this funny looking fuse. Its black, about the size of a fuse, has a little arrow marking on top, and the two legs are not side by side, but rather perpendicular....what the heck is this thing?

It is a relay, sometimes they can reset themselves when you remove them, sometimes they do not. I had this happen with my old Colorado, I just learned to to keep a spare in the console, also for the coorado, i had to go to dealer and get it, the ones at the local parts store were not the same.

is this what the pic looks like
http://www.mcmelectronics.com/conten...s/s4/DIODE.jpg

Do you have a CEL displayed? When my DIC temp display was the dashes the CEL code was P0128. Engine Coolant Temperature (ECT) Below Regulating Temperature. Replaced the T-stat and all was good again.

Can't tell you if it affected the A/c as it was Feburary in Michigan but I would think that if there were issues with the cooling system it (BCM) would prevent the A/C from working to avoid possible overheating/damage to the system.

That's the one....

never mind, its not the diode ...switched it with the wiper diode and still doesn't work. Not the relay either, as I switched that with the rear hatch release relay.... no change

Anyone have any ideas?

like he said replace the stat

There is no CEL .... will take it in on Monday get scanned.

A bad coolant temperature sensor could cause the gauge to be inop and since there would be no temperature reading to the BCM, it would command the A/C to not come on.

Check this thread for the procedure to replace the thermostat that a couple have already mentioned as being a likely cause - https://www.chevyhhr.net/forums/how-tutorial-library-21/how-save-%24350-00-thermostat-replacement-2-4l-p0128-24493/ - it may or may not throw the p0128 code via the engine check light.

Or as chevyMgr says, it also could be the temp sensor.

Where is it located?

OK, so this morning I'm off to go to work, and take the car in. The heat gauge pops back up after about 5 minutes of driving, and the AC starts working. On the hiway won't go over 78C (normally ran at 88C dead set and hardly wondered). Get into traffic and it starts to climb. Hit 90C before I decided to get off the hiway and keep moving. Got to work, and let it sit (all the way up to 93C) to come up. The Fan won't turn on now to cool it down! Clearly the T-stat is buggered hence the low temps....but now the fan going AWOL bothers me.

See the previously posted links on thermostat problems And how to replace it. Fan operation at 93 is normal.

T-stat changed...all is well

Glad you found the problem......

OK...maybe not "all" is well. Keeping a close eye on things, turns out the cooling fan only turns on if the AC is on. Without AC on, the temp keeps climbing. I didn't let it go above 100C. Once I flicked the AC on, the fan came on, and the temp dropped.

Might also explain why the T-stat failed in the first place.

Now, I have to try and figure out why this is happening ...... joys of high mileage cars :(

100C should be no problem (that's 212F, right?) On my SS, the cooling fan doesn't kick on until 216F if I remember right so yours is probably fine. I know that sounds high, but it is a pressurized system. It isn't overheating at that temp and the coolant won't boil till quite a bit higher temps.

Yeah.... I think you are seeing normal operation there......

It always turned on before that, it used to fire up and keep engine temp square at 88C with AC on or not.

Keep in mind I say 100C before I flicked the AC on to turn the fan on. Otherwise I have not gotten the cooling fan to come on without AC on. I can try to let it go a little higher, but as I mentioned, it never did this before. My guess is something is messed with it.

comes on at 103 .... guess I never noticed it before. Learn something new everyday :D

....now, off to change my stablizer links ...... again

where is this relay located on 2007 hhr?

be more specific. Relay for what, and what are you trying achieve?

Especially since the only relay mentioned had to do with one of the posters 'old Colorado' and wasn't part of the OP's solution.

I just bought 2007 HHR LS and having the same problems with temperature gauge and air conditioner. I already replaced the coolant sensor, didn't work, so today I am having the thermostat replaced. Is this the same as mentioned in the above posts?

T stat should fix the issue, ask the mech to use the correct GM stat! The ECM isn't happy with any of the other aftermarket ones!

Heat gauge and AC not working all of a sudden
 

Same thing happened to my wife, I found the relay in slot 15 in the fuse box under the hood was the problem, switched it with 18 to test and as soon as I plugged it in I heard the
AC motor kick on, quick trip to the auto store when its open and it will be good as new.

The same thing happened to me this weekend. On Friday morning, the A/C quit working all of a sudden. Half way home on Friday afternoon, it came back on as magical as it quit. It worked fine all weekend, but just a little while ago, it quit again, but this time I noticed that my temp gauge is not working at all and my digital readout is dashes. I was thinking that it may be the temp sender, but someone I read changed it without being the problem, I will try the relay as JTP suggested. thank you.If for some reason the relay does not do the trick, does anyone know where the temp sensor is located? I would appreciate it. Thanks.

If the temp gauge has flatlined, then most likely it's just a failed thermostat, I posted information in your other thread

Thank you Old Blue, now I need to find my other thread. (I am new to this) :)