'98 Voyager overheating

[dahirolla]

3.3L 1998 Voyager 200k miles

Overheats inside 20 minutes or so at any speed under approximately 40mph. It doesn't look like the fans are coming on. When the heat gauge reaches the top of the gauge, the alarm sounds and the heat warning light comes on the dash. Increase speed and the temp gauge goes down.

Also, when the heat gauge is in the high range, the A/C is blowing hot air.

I've not replaced the relays yet, and read several posts that mentioned two relays: the usual ones in the fuse box, and then another, more expensive one, closer to the fans.

Any other things I should check?

[Bear]

The fans are controlled by relays as well as a temperature sensor (on my '96 3.3 it is next to the thermostat housing). you can also try unplugging the fan motor connector at the fans and then running jumper wires (fused) from the battery and ground to the connector to see if the fan motor runs.

[dahirolla]

Excellent. I'll have a look.

[dahirolla]

Alright,

I've jumpered the fans and they run great directly from the battery. Not sure how to test the relays...any ideas there? Is an Autozone code reading a good idea?

According to other posts I've read the coolant temperature sensor can be a problem, but the PCM should turn the fans on when the sensor is disconnected. I've tried that and the fans fail to turn on. Someone lie to me and tell me it's not the PCM. :-D

All of the fuses in the fuse box are fine.

Thanks!

[dahirolla]

*bump*

Anyone have any suggestions as to what I might test next?

[Bear]

The temp sensor can be checked by removing the electrical connector and checking resistance at terminals A and B (the terminals are arranged at 3, 9,and 12 O'Clock, with A and B at the 3 and 9 position). With a cold engine around 70 degrees "F" the resistance should be between 7000 and 13000 ohms, with engine running,and warm (in the 200 degrees "F" range) you should have between 700 to 1000 ohms on the meter. I have no values for the relays, but look in the under hood relay box for the same relays (in my '96, many of the relays are identical part numbers).

[jpb53]

Fan relays are a known issue with these vans and is not located in the PDC. It is mounted to the inside of the frame under the air cleaner. It is attached to the frame because it needs a heat sink. Grey wire is power in to the relay. Green wire is power out of the relay. Jump grey to green wire and see if the fan comes on. If the MIL light comes on when the coolant temp sensor is unplugged the the computer is getting a signal. More than likely it is a bad fan relay.

[dahirolla]

Thanks for the suggestions, I'll check those things tonight when I get home from work.

What is the MIL light? I already have a system in place that warns me when my mother in law is in close proximity.

[jpb53]

MIL = malfunction indicator lamp.

[dahirolla]

So the "Service Engine Soon" lamp?

[jpb53]

Yes one and the same.

[dahirolla]

Ok, so I've pulled the fan relay. Now, how do I test it? I've already jumpered the fans directly to the battery, so I know the fans are functional.

[dahirolla]

If I understand correctly, my four lead relay should read open on one circuit and some resistance on the other.

This is a solid state relay, and I'm not sure what bearing that will have on what readings I should get with my multimeter.

The only non-open reading I get is the black wire to ground, and I get 140 ohms.

The light-green wire, which is the signal from the PCM, reads 0.15 volts when the van is running and the AC is all the way up. Perhaps I should be measuring amps instead? What should I be looking for there?

Any suggestions?

[jpb53]

If you ck a wire for resistance to ground the battery should be disconnected. 140 ohms is high. You should have battery voltage at the grey wire at all times even with the key off.

[dahirolla]

It was the cooling fan relay.

On the relay there are four wires, Gray, Dark Green, Light Green, and Black.

If the PCM is sending the signal to the relay, the light green wire should register 0.15 volts. To test this, unplug the relay, turn the van on, and max the A/C and blower. It might take a few seconds, but you should get 0.15 volts from the light green wire to ground.

The coolant sensor might also be the problem. Read previous posts in this thread for more details.

Thanks everyone for the pointers! I'm now back in good shape.

If I've provided mis-information in this post, please correct me so I don't send someone on a rabbit trail.