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-   -   Radiator fan inop (https://www.chevyhhr.net/forums/problems-service-repairs-42/radiator-fan-inop-65769/)

donbrew 10-28-2022 07:51 AM

The radiator cooling fan. It doesn't turn on with the AC, we don't know if it turns on at 217F.

royl 10-28-2022 09:49 AM


Originally Posted by donbrew (Post 931165)
I was trying to explain why my question about 220F was important. The question being is it the AC or the temperature or both that don't work.
Do you often monitor the cooling fan? How do you know it was working before the car wash?
The AC compressor will not turn on unless the blower is on, the Dark Green wire tells the computer that the blower is on. Probably not important here.
You could hot wire the cooling fan to see if it works. I suspect an error in installation.
The Dark Green wire from the ECM to the cooling fan relay turns the fan on and off It depends on several inputs.

The reason I know it was working before the car wash is the a/c was cooling before the car wash and after it stopped cooling. The compressor is running but without the fan it is just cool air, not cold. I did jump the hot and fan terminals on the fan relay and the fan comes on so the wiring to the fan has to be good. I just wonder if when the fan went bad did it damage the ecm? Something is not triggering the ground on the relay. I am going to try and find the wire from the ecm going to the fan relay and see if it is good. I see some of the years shows a diode in that wire and some don't on the wiring diagram but I don't know which years do or if that is the diode in the fuse box which is good. I was a mechanic for 50 years but these new cars stump me sometimes.

Oldblue 10-28-2022 09:55 AM

The A/C compressor is running, but without the fan just cool air not cold, are you saying the HVAC fan,inside the car isn’t running?

donbrew 10-28-2022 10:14 AM

No, he is saying that since there is no air flow across the condenser coils when not rolling the AC is not fully chilling.

donbrew 10-28-2022 10:33 AM


I was a mechanic for 50 years
That explains blaming computers.:propeller:
I doubt that the fan could possibly have any effect on the ECM; that is why there is a relay and fuse.
There is a diode in the compressor circuit , The fan relay might have an internal diode. I would get a new relay..
I don't know how a carwash could be the trigger.
How about checking ground continuity between the relay and ECM. Did you mean that you jumped ground to the relay and that triggered the fan, like test the relay not the fan.

royl 10-28-2022 12:01 PM


Originally Posted by donbrew (Post 931187)
That explains blaming computers.:propeller:
I doubt that the fan could possibly have any effect on the ECM; that is why there is a relay and fuse.
There is a diode in the compressor circuit , The fan relay might have an internal diode. I would get a new relay..
I don't know how a carwash could be the trigger.
How about checking ground continuity between the relay and ECM. Did you mean that you jumped ground to the relay and that triggered the fan, like test the relay not the fan.

No I jumped the power at the relay but I will try the ground also. I checked the diode in the fuse box and it was good. I swapped the relay out with a known good one. I am going to try and find the right pin at the ecm and check the trigger wire for continuity. I will get back to the shop tomorrow and try these things. I will also run it long enough to see if the fan comes on with engine temperature.

greg8453 10-28-2022 02:59 PM


Originally Posted by royl (Post 931183)
The reason I know it was working before the car wash is the a/c was cooling before the car wash and after it stopped cooling. The compressor is running but without the fan it is just cool air, not cold. I did jump the hot and fan terminals on the fan relay and the fan comes on so the wiring to the fan has to be good. I just wonder if when the fan went bad did it damage the ecm? Something is not triggering the ground on the relay. I am going to try and find the wire from the ecm going to the fan relay and see if it is good. I see some of the years shows a diode in that wire and some don't on the wiring diagram but I don't know which years do or if that is the diode in the fuse box which is good. I was a mechanic for 50 years but these new cars stump me sometimes.

OK. So what happened at the car wash that could have caused your problem? Can;t think of anything than call it a coincidence.
You also say the fan runs when you trip the relay and yet you replaced the fan?
Since long before computerized stuff we used diodes in all electric motors to filter the high voltage spike you get when powering or cutting power.

royl 10-28-2022 09:05 PM


Originally Posted by greg8453 (Post 931197)
OK. So what happened at the car wash that could have caused your problem? Can;t think of anything than call it a coincidence.
You also say the fan runs when you trip the relay and yet you replaced the fan?
Since long before computerized stuff we used diodes in all electric motors to filter the high voltage spike you get when powering or cutting power.

The original fan didn't run when I jumped the relay. I even applied power directly to it and it was dead. So I assumed a new fan would fix it but no luck.

royl 10-30-2022 02:14 PM

Well after more troubleshooting this is what I've found. The fan trigger wire from the ecm has continuity to the fuse box but not through the box. So I need a fuse box for sure. The a/c compressor clutch is burnt up so I need a compressor. The fan does not come on at 200 degrees which I assume is due to the fuse box. Now I just have to decide if a car with 215 thousand miles is worth the expense and work or if it's junk time.

RJ_RS_SS_350 10-30-2022 02:54 PM

Just to verify, you tested fuse #40 and relay #50?


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