APU Coolant Temp Overheating?

The fan for the A/C compressor is running. The fan for the condenser is not running at all. I read some TK service bulletin where they said it’s supposed to turn on at 150 or 170 F. I bought a new fan and installed it, but the problem is still there.

 

All my fuses in the black box are good. I also hit reset to clear the alarm codes.

 

I think I have my terms mixed up. I am referring to the fan that is installed next to the APU (not the one commonly installed on the back of the cab).

 

It seems like this will solve the problem. I’ll give it a try and report back.

 

PROBLEM SOLVED

Thanks everyone for your help.

@truckdriver31
You were right. The two valves under the hood need to be open when the APU is in use. Closing them causes the APU coolant temp to overheat. I recently did some work on my truck where I closed them off, and left them that way because I was incorrectly told that it wouldn’t make any difference. Thinking about it more, it really makes sense to have them open because it allows the APU access to about 13 gallons of coolant. The temperature by the thermostat now fluctuates between 125 to 135 F, which is good. The alarm gets triggered if it goes over 170 F.