electric fan problem

[mike]

Would anyone know why the electric fan on my 84 vette starts as soon as I turn the key on? I have replaced the high pressure switch on the compressor and the fan temp switch. Is the high pessure switch to be open until there is pressure built up in the compressor? Is it possible that the fan relay has gotten weak and closes as soon as the key is turned on?

 

[Schrade]

Welcome onto the boards there...

Fan coming on at startup is a diagnostic clue for later C4's (like forgetting to plug back in the MAF connector, for one :duh ). Also, if the A/C is on, the secondary (?) cooling fan will come on. If also for '84, I'm not knowing that.

Do you have an SES light? Put a paper clip in the ALDL and check...

 

[vetteoz]

84 has mech switch only ; no ECM control
So if the two switches are confirmed good ; either relay is bad or the wires to A/c switch or temp switch are shorted
to ground causing relay to close key on

 

[Schrade]

Pictures are GOOD yup!

Do this on a COLD motor. Disconnect ECT switch at splice C100. Turn on the key. If the fan does NOT come on, the ECT switch CIRCUIT is shorted to ground, or the ECT switch itself is broken in the 'ON/CLOSED' position. Replace.

If the fan DOES come on, then the A/C pressure switch is stuck in the 'ON/CLOSED' position, or that circuit is shorted to ground.

The ENGINE COOLING FAN RELAY itself CANNOT be stuck closed between 902 and battery, because the fan would then have power even with the key OFF.

 

[mike]

Thanks for all the help, it helped to figure out the problem. The parts store was selling me high pressure switches that were closed instead of opened. Good thing they kept exchanging them. Anyway it works great now, now only if the weather would clear up so I can enjoy it. Thanks again!!!

 

[boomdriver]

Would anyone know why the electric fan on my 84 vette starts as soon as I turn the key on? I have replaced the high pressure switch on the compressor and the fan temp switch. Is the high pessure switch to be open until there is pressure built up in the compressor? Is it possible that the fan relay has gotten weak and closes as soon as the key is turned on?

you ARE talking abput the radiator fan? are'nt you?

if so, that fan has a switch in the hi pressire line of the a/c en route to the evaporator. the plug simply needs to be loose or off to make the fan run all times.

if not that, fan relays love to die when energized leaving the contacts stuck in place running whatever they did. leaving your fan circuit hot with key on always. Key on is all it takes to have a running fan now.

enjoy.

 

[mike]

you ARE talking abput the radiator fan? are'nt you?

if so, that fan has a switch in the hi pressire line of the a/c en route to the evaporator. the plug simply needs to be loose or off to make the fan run all times.

if not that, fan relays love to die when energized leaving the contacts stuck in place running whatever they did. leaving your fan circuit hot with key on always. Key on is all it takes to have a running fan now.

enjoy.

thanks for the post, but I have already got the problem fix. the high pressure switch was bad, causing thefan to run all the time. finally found the right switch, now the fan only runs when its supposed to.