[DLow]

So ive just recently had my water pump go out, I had the whole cooling system replaced(aside from radiator); pump, thermo, sensor. everything was fine for about a week when all of a sudden, my temp gauge failed to C, check engine light came on, and my radiator fans run constantly as long as the car is on. The interior blower system also will only blow cold air, even when set to the hottest setting. I went ahead and replaced the battery as well, but at this point I'm stumped, the car seems to drive fine and to the best of my knowledge hasn't overheated. any help would be greatly appreciated!!!

 

[DrivenDaily]

With the heater blowing only cold, that suggests that either there's not enough coolant or that the thermostat has failed open. If it was just the sensor, the radiator fans would run constantly, but at least you'd have heat.

Was the heater working normally prior to this happening?

 

[DLow]

With the heater blowing only cold, that suggests that either there's not enough coolant or that the thermostat has failed open. If it was just the sensor, the radiator fans would run constantly, but at least you'd have heat.

Was the heater working normally prior to this happening?

Prior to replacing everything, yes. And I believe after it was as well. If Im driving for a while, it will eventually 'warm up' and blow 'warm' air but not hot by an means and not like it was before all of it.

 

[DrivenDaily]

I have to wonder if the coolant is completely full, if there's a clog somewhere, or both.

I doubt that the heater temp door failed coincidentally, but it could happen.

 

[DLow]

I have to wonder if the coolant is completely full, if there's a clog somewhere, or both.

I doubt that the heater temp door failed coincidentally, but it could happen.

If there were a clog, wouldn't it be overheating because of improper circulation? The coolant is filled up to the full line. Has been since I replaced the water pump and thermostat

 

[repairman54]

Scan tool will tell you what the PCM is seeing from the coolant temp sensor. If aftermarket it can be bad right out of the box. GM sensors only for every sensor.
Fans on right away is the sign of a bad sensor.
Thermo installed correctly or the right one? That's what controlled engine temp. Non contact temp. gun makes it easy to check. Aftermarket thermo could have failed as some fail safe and stay open.
Sounds like more than one thing malfunctioning is happening.

 

[DLow]

The sensor was aftermarket not OEM. The thermostat was a failsafe thermostat. not sure how I would have installed it incorrectly, elaborate? My only and next step is to try to get the codes scanned and run through all of that.

 

[JLDickmon]

If it sets a P0128 (thermostat rationality) code, it will do everything you just described. Have it scanned.

 

[DLow]

If it sets a P0128 (thermostat rationality) code, it will do everything you just described. Have it scanned.

Just scanned, that's the exact code, so now it's back to the thermostat or the sensor. Quite frustrating as both are brand new, and not operating properly

 

[DrivenDaily]

Scan tool will tell you what the PCM is seeing from the coolant temp sensor. If aftermarket it can be bad right out of the box. GM sensors only for every sensor.
Fans on right away is the sign of a bad sensor.
Thermo installed correctly or the right one? That's what controlled engine temp. Non contact temp. gun makes it easy to check. Aftermarket thermo could have failed as some fail safe and stay open.
Sounds like more than one thing malfunctioning is happening.

The sensor was aftermarket not OEM. The thermostat was a failsafe thermostat. not sure how I would have installed it incorrectly, elaborate? My only and next step is to try to get the codes scanned and run through all of that.

Just scanned, that's the exact code, so now it's back to the thermostat or the sensor. Quite frustrating as both are brand new, and not operating properly

You just might find that the aftermarket sensor isn't up to the task. But then again, it might be.

@repairman54 knows his stuff. He recommends only GM sensors for a reason.

There are too many threads and posts on CMF about folks who used non-GM sensors and thought that the issue just had to be elsewhere since the parts were new. Only after some disbelief and finally checking did they discover that a new GM sensor actually fixed the issue.

We're not shills for GM or any other brand. We just share what we've learned. YMMV.

 

[DLow]

Well it seems like the thermostat is stuck open, I'll start there and then try the sensor