ubiquitus

Well, these are the problems I chose to work on today. The car overheats due to neither of the fans turning on and when I scan with either Datamaster or Freescan, I get a DTC 77 Cooling fan relay control circuit. Also, since I've noticed the fans not coming on, the reverse lockout solinoid has been a pain and kept me from easily going to reverse

I've tested the fans themselves and they work with direct power. I've also checked all of the under hood relays and they all work correctly. Also, I've tried jumping pins 5 and 6 on the connector and they didn't come on. Any suggestions? I'd love to be able to drive through town again lol.

slopokrodrigez

This is going to be tough unless you can use one of your scanners to force on the fan. You need to look at the fan control line between the PCM and the relay. On pin 85 is the dark green wire. This line is grounded in order to turn on the relay. You can use a test light connected to the positive battery terminal. When this line is "on" it's grounded and at that time the test light will come on if the other end is connected to +12.

If you find the relay socket pin 85 is not grounded when it should be, go over to connector c100. Its the 10 pin connector right near the PCM. Back probe the dark green wire on both sides of the connector. Again, this line is grounded to be active so don't look here for 12 volts but rather look fro ground. If one side is ok and the other is bad, the connector is not making good contact.

BTW, you did check the fan fuse #6 didn't you?

The connector C100 is currently giving me fits with the AC compressor control.

shoebox

If they did not come on when you bridged the pins on the DLC, then you have a computer or relay control wire/connection problem.

ubiquitus

Thanks for the responses guys. I'll test those connectors today and see if I can find the problem.

Injuneer

Both the fan relay and the reverse lockout are on the same fuse on the 95's. See "slopok"s question re Fuse #6.

ubiquitus

I've tested fuse #6 along with all other fuses both under the hood and in cabin and they're all good.

ubiquitus

Slopok, I tested the green wire on the C100 connector for ground on both sides using one end of the probe on +12V and the other on the connection with the c100 disconnected. The side toward the fuse box grounded fine and showed 12v, the other side toward the pcm didn't. Is the wire supposed to be grounded through the PCM? The same was true for the blue wire. I've also left the C100 connected and shoved a paperclip to the connector on the pcm end of the c100 and tested for ground there and it tested fine through the connector. I tested the resistance of the dark green wire going from the C100 to the fan 1 relay and it showed 0 (good) using the 2k/diode setting. I tested the blue wire and it showed 0.049, which means its slightly resistive. Is this a problem? I'm testing the PCM end of those wires now. Am I right in testing them with the car off and battery connected or does it not matter. Thanks for everyone's help.

ubiquitus

Ok, after testing nearly everything, I found that none of the wires had any shorts or excess resistivity from the pcm to the fans and all relays worked. So, I tried to turn the fans on manually by grounding the pcm wire of fan relay one and it just made a big spark. Then, i topped the radiator off again from the t-stat housing leak I fixed the day before, then ran a scanner to see if the codes were still there and they weren't. The fans engaged in the reading feature of the CATS pcm flasher/reader utility. And, when I started it, the reverse when right in like nothing was ever wrong. Hopefully it'll stay fixed for a long while and it was just the coolant being too low for a while, but why would this kill the reverse solinoid?

slopokrodrigez

Me thinks your problem was just what I'm going through right now with the 10 pin connector crapping out. Only on my car it's the AC and it's 90 degrees with 200 percent humidity. Lucky it's not my main vehicle.

If you've not done anything really to the connector, it's just a matter of time before the problem comes back. Sorry.