1998 Plymouth Breeze - Radiator Fans do not come on when AC is turned on

Tiny
1998BREEZE
  • MEMBER
  • 1998 PLYMOUTH BREEZE
  • 4 CYL
  • FWD
  • AUTOMATIC
1998 Plymouth Breeze 2.4L

Radiator fans do not come on when AC is turned on (ac compressor does come on). Fans test ok (direct to battery). Power at the radiator fans fuse (fuse block under the hood). Ground at power clip ok, no power from positive leads when AC is turned on.

Where else is there to diagnose problem?
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Sunday, June 5th, 2011 AT 8:48 PM

3 Replies

Tiny
CARADIODOC
  • EXPERT
There's two different fans and two different fuses, numbers 9 and 19. Both relays are turned on by the Engine Computer. Start by troubleshooting the low speed fan. The high speed one might just not be up to the required temperature for it to turn on.

Although it's not common to have a relay failure, that's the easiest thing to test by swapping it with a different one like it. You might be able to feel it click if you put your finger on it while a helper switches the AC on and off. Whether or not it clicks on will determine where we go next.
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Sunday, June 5th, 2011 AT 9:20 PM
Tiny
1998BREEZE
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No helper available so I swapped out the relay with wiper (hi/lo) relay and everything is still the same - fan do not come on & wipers work fine. #9 and #19 fuses are both hot.

Any suggestions on the next step?
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Sunday, June 5th, 2011 AT 11:15 PM
Tiny
CARADIODOC
  • EXPERT
First of all, I screwed up, ... Again! Fuse 19, a 40 amp, feeds the contacts of BOTH relays and fuse 9, a 10 amp, feeds the coil of both relays. More on those circuits in a minute.

One fast thing to try is with the engine running, unplug the two-wire coolant temperature sensor near the thermostat housing. That will set a fault code and turn on the Check Engine light, but it should also cause the fan to turn on. If it does, you'll know the computer is working and has control of the relay. If it does not turn on, the best approach is to find a scanner that can turn the relays on and off to see if the computer responds.

Another way to test the switched part of the relay circuit is to ground terminal 86 of the low speed relay. This is different numbering than I'm used to seeing, and there have been so many mistakes in the service manuals that it's better to describe how to find that terminal. Pull the relay out and measure the voltage on the four terminals. Two of them should have 12 volts with the ignition switch in the "run" position. If you can sneak your voltmeter or test light probe under the relay when it is reinstalled, and can get the voltage readings on the two remaining terminals, one of them should now also have 12 volts. That's the one to ground. Touch a grounded wire or use a paper clip as a probe to touch that terminal. That should make the relay click on and the fan should run. That will prove which part of the circuit has the problem.

I apologize that I have to leave for a couple of hours, but I'll check back as soon as I get back.
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Sunday, June 5th, 2011 AT 11:56 PM

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