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GM Tech (Cam)
GM Tech (Cam), Pontiac Technician
Category: Pontiac
Satisfied Customers: 29427
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2000 pontiac montana: 3.4 Van is overheating..Cooling fans..AC

Resolved Question:

2000 pontiac montana 3.4

Van is overheating. Cooling fans are not coming on. I turn on AC, neither fan comes on, 1 is supposed to when AC is turned on. Checked fuses for cool fan 1 and 2, both fuses are good. Checked wiring to fans from fuse box. Found the wire connector in between the fans was burnt. Rewired the wiring at the point. Could find nothing else. Opened up one of the mini-relays, #10 (pn3604) and tripped the relay myself. The RH fan came on (passenger side). I then tripped the #12 mini relay myself and the same fan came on. LH fan never came on. What now?
Submitted: 7 years ago.
Category: Pontiac
Expert:  GM Tech (Cam) replied 7 years ago.
Welcome. There are 3 relays and 2 maxi fuses for the cooling fans on these vans, and looking at it, there is no simply way to trip the relays to get the left fan on as it runs through 2. I recommend that you run power and ground to the left motor manually to see if it runs. If not, that could be the cause. Also, is the check engine light on?
Customer: replied 7 years ago.
The check engine light was on last night, I pushed the wrong button on by obd2 scanner and erased the error code, but the check engine light has not come back on. So you think possibly that the LH fan could be causing all the overheating problems? I just curious, but would that keep the RH fan from coming on.
Expert:  GM Tech (Cam) replied 7 years ago.
IN low speed, they run together so it is very possible.
Customer: replied 7 years ago.
I Not the shapest knife in the box, but whats a good way to run power and a ground to the LH fan to test it.
Expert:  GM Tech (Cam) replied 7 years ago.
I would get 2 wires, one with a 20amp fuse, run one from the terminal in the receptacle of the motor to ground and the other to a power source.
Customer: replied 7 years ago.
I replied way too soon last time. As soon as I replied I came up with a idea. But the other fan does work. what now?
Expert:  GM Tech (Cam) replied 7 years ago.
The right fan is controlled by a single relay and that relay can make it run on its own or in series eith the other relay depending on the second relays. What was your idea?
Customer: replied 7 years ago.
I switched the wiring around from rh fan to Lh fan, that was my big idea. Should I be possibly looking at the pcm or the other relay (3602) as maybe being the problem, I know at this point that the relays are not being tripped and both fans would work if they received power. So what do you think I should look at now.
Expert:  GM Tech (Cam) replied 7 years ago.
OK, so you switched the harness around, did what you did before and the other fan ran?
Customer: replied 7 years ago.
yes
Expert:  GM Tech (Cam) replied 7 years ago.
OK, so the fans work, but what caused the wires to be damaged that you repaired? Is the wiring to the left fan motor all good? Before you spend the money on a PCM that may not even be bad, it may well worth your money to have a quick scan tool diagnosis done. With your overheating, does the dash show it is hot or is the coolant just boiling?
Customer: replied 7 years ago.
Dash shows hot, now the van wont start at all.
Expert:  GM Tech (Cam) replied 7 years ago.
Did it stall on its own or will is just start now? Does it crank over?
Customer: replied 7 years ago.
It is starting now, fans still do not come on though
Expert:  GM Tech (Cam) replied 7 years ago.

OK, I don't want to say this, but you need a scan tool to command the fans on and see if they respond to the PCM controls.

HERE is the cooling fan diagnosis.

Customer: replied 7 years ago.
Fixed it!!!   I changed out the other mini relay #9 (3602). Bam! fans came on. The reason the van wouldnt start was I didnt have one of the relays down all the way. Thanks for your help. Is a scan tool different than a obd2 code reader?
Expert:  GM Tech (Cam) replied 7 years ago.
A code reader is as the name suggests, it reads codes. Scan tools are bi directional and can command the pcm to perform functions and read the data from the data stream. They are also 2000-4000.
GM Tech (Cam) and 6 other Pontiac Specialists are ready to help you
Customer: replied 7 years ago.
Thanks and have a nice day.
Expert:  GM Tech (Cam) replied 7 years ago.

You are welcome. You can always reply to this post if you should need more information even after you accept.

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