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Discussion Starter · #1 ·
I have a problem that I cannot Figure out. I am a Mechanic, I do know what I am doing. I just need some help. Alright, 1988 camaro 305 with a 350 Engine. (305 computer & Injecotors) The Coolant Fan Will Not kick on Ever. I replaced the Relay on the firewall Awhile ago (before the fan died) The old one was clicking on and off all the time no matter what the temp. was. The motor and everything on it is 45,000 miles old.

I have a 150* thermostat. So Driving down the road is not a Problem at all it stays Under 150, Until I get into traffic and/or stop and sit. Ive hot wired the fan, so the Fan it self is good. Fuses are Good.

I am Replacing the ECM as well as the injectors for a 350. In my research I found that it may be the ecm, is that true? I dont know where to look.

The Relay on the Fire wall is getting power.

The Switch/Sending unit on the manifold has power but I canot get a ground. is the Ground Controlled by the ecm?

Thanks a Bunch, Nick Hall
 

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Nick...

Yes, The ECM will set the ground for the fans to kick on. A buddy just ran into the veery same problem on his Pontiac. Everything tested good so concluded that it was the ECM. Changed it and the fan worked as it should.


Kev
 

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Remember, that GEN F-body has minor cooling problems anyway due to inadequate flow of air thru the radiator. An aftermarket 4 core rad and a PUSH fan vice pull fan works better....IMHO
 

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The fan(s) should come on when DEF or A/C is selected. Fan relay controlled by the ECM.

If dual fans, one is controlled by the heat sensor/switch in the engine block/manifold. It closes at some 225*F-235*F, and fan comes on. The other fan is controlled by ECM getting input from a two-wire coolant sensor. The ECM relay has battery on one side of the coil and the ECM has the return.

When no fan needed, the ECM has a high voltage. Temp satisfied, ECM places a low, 0.5 volts and this action energizes the relay, fan on. Relay has a large gauge wire for fan power to one contact, and the other to the fan motor. Ground is supplied at the fan plug.

Or, for ther engine fan, the engine has a temp switch and ground is through the body threads to engine, closes when temp is reached, 230*F(?), energizes the relay, fan on.
 

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Discussion Starter · #5 ·
Like I said, I am replacing the ECM, I have the new one sitting next to, I am waiting for the prom which I'm getting from a Friend who makes Custom Chips. I will Update this thread when the Chip gets here and the ECM is in. I am Guessing Tuesday.

If that doesnt Work, I will buy a new Temp. Unit.

Thanks A Bunch. :beers:
 
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