Cooling Fan Wiring Issue

[DeLorean937]

I'm having a strage problem with my cooling fans in which I am trying to diagnose.

When jumping the fans at the Otterstat, the fans do not come on until I turn the A/C on. After switching off the A/C, the fans still stay on because of the jumper. All in all, the fans only will come on a operate when I switch the A/C switch. Any ideas of what could be the issue. I looked at the wiring diagrams and everything seems to be connected in the right order. I am a little confused about fuse #5 which the fans run on. I tried looking at the full wiring diagram but I dont know where fuse 5s lines distribute to.


-Robert

[David T]

If the connectors on the Otterstadt switch are corroded and green you are probably not getting a good connection. Clean them up and try again.
David Teitelbaum




I'm having a strage problem with my cooling fans in which I am trying to diagnose.

When jumping the fans at the Otterstat, the fans do not come on until I turn the A/C on. After switching off the A/C, the fans still stay on because of the jumper. All in all, the fans only will come on a operate when I switch the A/C switch. Any ideas of what could be the issue. I looked at the wiring diagrams and everything seems to be connected in the right order. I am a little confused about fuse #5 which the fans run on. I tried looking at the full wiring diagram but I dont know where fuse 5s lines distribute to.


-Robert

[DeLorean937]

Its actually a new Otterstat I installed a few months back

[amuderick]

I had the same problem. The solution is simple and cheap: replace the diode. Part #110061. It is easily swapped out in wiring area behind the passenger seat.

I replaced the Otterstat. Did no good. Jumping the otterstat connectors did no good. Only turning on the A/C would activate the fans. That was a problem in traffic in cool weather because the compressor would not turn on and the temperature would climb.

Replace the diode. Mine had no conductivity in either direction.

[Bitsyncmaster]

Are you taking about the radiator fans or the cabin circulation fan?

The otterstat jumpered should always turn on the radiator fans with the key in the run position. You probably have a disconnected diode or bad diode. The diodes are in the harness to the right of the relays.

[DeLorean937]

Thanks so much for responses. Ill check it out tonight since work has been crazy. Ill let you guys know what I figure out checking the diodes.

[DeLorean937]

Back from the garage and found the diodes. One was melted beyond anything the other seemed ok. I measured the voltage at each end on the burnt diode and saw the side that had a female connector was measuring 12v and the other with the fans turned on was measuring 9v.

Is this normal?

[Bitsyncmaster]

Back from the garage and found the diodes. One was melted beyond anything the other seemed ok. I measured the voltage at each end on the burnt diode and saw the side that had a female connector was measuring 12v and the other with the fans turned on was measuring 9v.

Is this normal?

The most common test is using an ohmmeter. One direction conducts (low ohms) and the other direction is open (very high ohms). But if you measure the voltage when the circuit is powered, you should see about 0.7 volts over the diode.

[DeLorean937]

Thanks for the advice! I went ahead and knocked out the test with the meter and found it was good. Installed the unit, tested once more and it works perfectly now. Better than new!

Another issue I had that, I thought this would fix, is all the side instrument cluster lights are still not working. Including the side marker indicators. Is it possible the burnt diode burned the back of the instrument circuit since it is attached to fuse #5

[DeLorean937]

I forgot to mention that ive removed the cluster and tested the points of contact on the connector. Using a test light I tested the points and the test light switches on and off. Maybe a bad ground?

[Bitsyncmaster]

I forgot to mention that ive removed the cluster and tested the points of contact on the connector. Using a test light I tested the points and the test light switches on and off. Maybe a bad ground?

The most common problem with those instruments and lights are the copper foil connectors get mashed when you put the cluster back in. There are two or three connectors so since your seeing problems with the left side, it must be one connector.

[DeLorean937]

Its actually both sides looking at it. Lighting up top works and all gauges work.

[Bitsyncmaster]

Its actually both sides looking at it. Lighting up top works and all gauges work.

You would need to list all the faults and then see if any common connection would relate to most of those faults. It would just take a little study of the schematic.

[DeLorean937]

I took your advice and checked out all the connections on the 2 harnesses for the instrument cluster and found that they all operate. I had an old circuit laying around from another binnacle so I tested that and most, not all of the lights started working.

That tells me the printed circuit is bad, correct? Can these be fixed or is it worth spending the $80 for a new one?

[jawn101]

I took your advice and checked out all the connections on the 2 harnesses for the instrument cluster and found that they all operate. I had an old circuit laying around from another binnacle so I tested that and most, not all of the lights started working.

That tells me the printed circuit is bad, correct? Can these be fixed or is it worth spending the $80 for a new one?

Well if most but not all of the lights work, is there anything common between the ones that don't? Are the nonfunctional ones different from one printed circuit to the other? Is the printed circuit you tested a known good one? Which lights don't work? How did you test them? Are you using LEDs in place of the incandescent bulbs? If so, remember that LEDs are polarized and need to go in the right way around.