To rule out the T stat you need to know what the actual temp is, like through a scan gauge attached to the OBD II port (the dashboard gauge is fairly useless for this). You would be looking for a sticking T stat that causes the temp to spike high, but opens enough not to completely overheat.

If the truck runs fine except for this one problem, I would put the PCM low on the list.

You could also have a bad AC clutch, or a short in the AC circuit.

 

I had the same situation recently...AC OFF message, along with the Check Engine Light..switched out my thermostat (AutoZone - $35)...problems fixed!! Hope that helps!!

 

OK I need help... my AC OFF light comes on intermittently, then AC stops working and temperature gauge stops working - sometimes after 5 minutes it will come back on, most of the time it doesn't. I just had the AC harness recall work done, and was hoping that would fix the problem but it didn't. Dealer wants $600+ to fix it - he said I needed new thermostat, coils and plugs. He did not say anything about the ECT sensor which is what I'm seeing over and over again as I google the symptoms. Can anyone tell me if they've successfully fixed the same problem that I'm having? I have a 2008 H3. Thanks.

 

does it drop to zero?

when working is the temp at mid point, normal?
is coolant ok?
i dont trust anything i hear from dealers.
the recall harness was for the blower motor speed only, not air control.

 

Yes temp gauge goes to zero. Coolant is good but it runs hot, over halfway mark. I'm female so when I go to dealer I feel pretty intimidated - that's why I'm here! LOL

 

running hot will turn off air. recheck coolant in morning,cool. check,fill at radiator cap ONLY WHEN COOL!

on other cars i had gage go low when water was too low to heat sending unit. im guessing.
sending unit? bad?

 

The guy that last posted in it almost a year ago said they replaced the T Stat and it fixed it.

It might be a T Stat issue, but as I posted earlier, it is more likely a bad sensor, or the connection to the sensor. Cheap and easy fix either way. A bad T Stat happens when it gets stuck (they will not close all the way) which causes the truck to take much longer to get up to full temp, and that throws a CEL P0128. No Check Engine Light, less likely to be a bad T Stat.

You came here for some help. My first suggestion is to NEVER, never, throw about 10 more NEVERs in there, take your vehicle to a Dealership for repairs unless it is under warranty, and the repair is a warranty repair. My second suggestion is.... my first suggestion again. Dealerships are in the business of SELLING, they are trying to sell you repairs you do not need. Coils and plugs have nothing to do with your issues. Spark plugs and coil on plug packs are cheap, so is the T Stat. So they are looking at you like $350 just walked in. The parts are $15 plugs, T Stat $27, coils $130, and antifreeze $53. The T Stat book time itself is 2.1 hours. The H3 is about the easiest vehicle made to change plugs and coils, book time is .5 hour or less.

Your truck does not run hot, anywhere between 1/2 - 3/4 on the idiot gauge is normal, it is supposed to run between 185-195F. The factory T Stat was rated 5 or 10F cooler than the current replacement, so a new one bumps temp a tad higher. Mine used to run 188F on the original T Stat, now it runs 195F.

If you are sure that the coolant level is full, I would take your truck to a reputable local repair shop, tell them your symptoms, and that your research .... talking w/ family & friends leads you to believe you need a new Temp Sensor and possibly a new T Stat. The Temp Senor is a $25 part, pretty close to the T Stat price. Since they will drain some coolant to get to the Temp Sensor and they have to drain a bunch to do the T Stat, you might just consider getting a price for both. Should be something like $250.

My motto is try the easy (& inexpensive) stuff first. Doing the Temp Sensor is simple and cheap and probably will take care of it, but if the price to add the T Stat swap in while they have the truck is reasonable, you may want to do that too.

Good luck.

 

THANK YOU!!! I will find a reputable repair shop and see what they can do. I know how dealers operate and I'm very intimidated by the terms that I don't understand so that's why I reached out here. I don't feel quite as stupid here (although I will be googling some words after this post!). Thank you again and I will report back on results in case others can use the info. :-)

 

Ok so is the ECT the same thing as a T Stat ???

 

No

Engine Cooling Temperature sensor.

T Stat = Thermostat.