FAN Operation - 84
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Pro
Joined: Dec 2002
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From: 84 383 XFire Chandler, AZ
FAN Operation - 84
Here is the deal.
My fan relay roasted - literally. So I replaced it with the $16 kit from Ecklers, it uses a relay from a 88-95 plus a new weather pak connector. Everything was fine and yesterday I had the AC charged back up and now the fans will not turn off. I guess that is better than not turn on. I pulled the connector from the temp switch on the passenger side head to test that temp switch but no joy.... the fan still stays on. So I am thinking the relay went bad..... What else controls the fan I know about the AC turning the fans on when the AC is turned on. I checked the status bits win WinALDL and I can see the AC ON check mark change in the status when I cycle it from inside the car and the I can hear the compressor kick in. Is it possible it is something other than the relay?
My fan relay roasted - literally. So I replaced it with the $16 kit from Ecklers, it uses a relay from a 88-95 plus a new weather pak connector. Everything was fine and yesterday I had the AC charged back up and now the fans will not turn off. I guess that is better than not turn on. I pulled the connector from the temp switch on the passenger side head to test that temp switch but no joy.... the fan still stays on. So I am thinking the relay went bad..... What else controls the fan I know about the AC turning the fans on when the AC is turned on. I checked the status bits win WinALDL and I can see the AC ON check mark change in the status when I cycle it from inside the car and the I can hear the compressor kick in. Is it possible it is something other than the relay?
Team Owner
Joined: Mar 2001
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From: Cincinnati, Oh USA
The ECM grounds the fan relay coil to turn on the relay which supplies power to the fan motor. The ECM turns the fan on when the a/c is turned on and/or if the coolant temperature exceeds 228 F. The ECM gets its coolant temp information from a temp sensor on the front of the block, high and almost in the center. The temp sender on the right side of the heads operates the dash temp gauge only! You may have a defective sensor or a defective harness connector (moderately common occurance). A scan tool will read out what the ECM temp sender says and you can compare that with the dash temp gauge (there will always be a slight difference between the two). The ECM could also have a defective transistor that grounds the cooling fan relay and keeps it on all the time.
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Joined: Sep 2000
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From: The Top of Utah
The electrical circuit for the fan on an '84 is simple and straight forward, as the manual shows. The ECM has no part in the fan operation. Circuit #335 at the fan relay terminal "B" can be grounded by one of two means to close the relay and run the fan. One method of grounding is when the temp switch in the right head closes because the target water temp has been reached. The other way is for the pressure switch at the compressor to close. Either action grounds circuit #335 and closes the relay. Since the fan doesn't stop by pulling the fan switch wire, the relay must be being grounded by the other possible ground source: the compressor pressure switch. I'll bet if you disconnect the plug at the A/C compressor pressure switch, the fan will stop (assuming that the temp switch hasn't closed).
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RACE ON!!!
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From: 84 383 XFire Chandler, AZ
As it turns out it is the high pressure switch on the compressor. With the AC not on there is continuity between the two pins which means On and high pressure switch should be open. I can't find the "old style" single terminal switch. I also tested this by simply pulling the connector and letting it cycle thru a fan on and fan off with the motor running.
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From: The Top of Utah
Originally Posted by elkabong
As it turns out it is the high pressure switch on the compressor. With the AC not on there is continuity between the two pins which means On and high pressure switch should be open. I can't find the "old style" single terminal switch. I also tested this by simply pulling the connector and letting it cycle thru a fan on and fan off with the motor running.
Originally Posted by 65Z01
On my '88 that A/C pressure switch is NC configuration (switch is closed when A/C pressure is on) so that when I pull the plug from the switch the ECM will run the fan.
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Joined: Dec 2002
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From: 84 383 XFire Chandler, AZ
I was mistaken it is not the high pressure switch. That is in back of the AC hooked into the AC lines. CFI is right, it is an additional fan switch and when open (ac off) it will not force the fans on, closed will. A simple test would be check continuity with the AC off then on. Off 'open' On 'closed'. My problem is the moron that charged the AC - over charged it and the switch is 'closed' all the time so the fans are always on. If I disconnect the switch (open) the fans operate normally. I get the pleasure of taking it to the dealer explaining what is happening having them fix it and then go pitch a fit at the AC shop. I will get my $$$ worth at the AC shop - I will show up at 3pm when most folks are picking up their vehicles.
I got the number to Tech Support for 4Seasons (AC fan switch)from my parts guy at CarQuest. I called them and this is what they told me, the switch opens at 37lbs (ac off) and closes at 43lbs (ac on).
I got the number to Tech Support for 4Seasons (AC fan switch)from my parts guy at CarQuest. I called them and this is what they told me, the switch opens at 37lbs (ac off) and closes at 43lbs (ac on).
