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2007 Pt Cruiser ac cooling fan not turning on

63K views 5 replies 5 participants last post by  schelled 
#1 ·
I have a 2007 PT and the ac cooling fan is not turning on even though the high side pressures go well over 300 psi. I am trying to diagnose the problem but the Mitchell manual shows a cooling fan module in front of the rad for 2007 but I have two relays on the back side of the fan shroud. If I can find the proper diagram I can see if the relay is being turned on or if I need another fan motor. The engine is not overheating so I am assuming that the 2nd motor speed must be working fine. Does anyone know which wiring diagram is the correct one for this vehicle?
 
#2 ·
This doesn't answer your question, but I think it will help.

Three things to check, the fan motor itself may have failed, the relay that switches the fan on my have failed, the pressure switch/sensor in the AC system may have failed and thus doesn't signal the fan to turn on.

Relays, you usually have multiple of the same relay, so you can swap them around and see if its the relay.

Fan, you can jumper the contacts to battery power and see if the fan comes to life.

Some fans have a solid state relay, basically a huge transitor pac that uses Pulse Width Modulation to control fan speed. They can burn out, and its often NOT in the PDM box with the other relays, its wrapped up in electric tape on the harness going to the fan.

I'm guessing you could measure resistance on the high side pressure sensor and see if changes as the AC turns on and pressure builds, or if it goes from infinite resitance to zero if its switch and NOT a sensor.

Finally, you have checked for stored DTC's in the PCM?
 
#3 ·
The 2007 should have a TIPM (totally integrated power module) with no internal radiator fan speed relays. The TIPM uses solid state drivers to control the fan shroud mounted fan module for hi and lo speeds. It is 'smart' power management.
Fuse #15 is the module supply fuse. The Dk Bu/Lt Gn wire controls the low speed signal to the module and the Dk Bu/Or wire controls the hi speed signal to the module. The Bk module ground wire must also be a good ground.
I believe that the fan module is serviced only as a radiator fan assembly. Diagram here:
2010-03-23_221820_130933739.gif
 
#5 ·
schelled said:
So the things on the rad shroud are modules, not relays? The diagram you attached is the same one I have. I will pull the fan out and check the motor. It was replaced once already under warranty, from what I have read that is a common problem.
According to ImperialCrown, Yes. I "believe" (don't know for sure, it's true for my Neon) they are just super duty transistors. So, since they are solid state, and you'd want to confirm this, unless they are cooked, they are likely still good.

Check the fuses like ImperialCrown suggested as well. The new kinds of fuses can look fine in their slot, you have to pull them out and hold them up to the light to see that they have burned out.

And do check the fan and make sure it is NOT bad.

BUT, don't forget, there is one more link in the chain to turn this fan on. So if the fuse is good, the fan is good, the modules are good, you need to check the last one as well.

The pressure sensor/switch in the AC lines itself. That fan is NOT wired to the AC switch on the dash, that when you turn on the AC you also turn on the fan. That fan is either controlled by a pressure switch in the AC, that when AC pressure builds high enough it turns on to cool the condenser, OR the PCM is monitoring AC pressure through a pressure sensor in the AC and when the PCM sees pressure build in the AC it turns on that fan.

Regardless, if that sensor or switch is bad, your AC fan won't turn on. It happened on my '91 Mini-Van, the switch on the AC can go bad. Later mopars, they went with a pressure sensor and the PCM monitoring the pressure and PCM turns on the fan.
 
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