Please help w/erratic front wipers on 99 Explorer? Replaced relays and switch - does the GEM get involved?

[dbcreed]

Have a 1999 Ford Explorer XLT 4.0 SOHC. The front wipers are erratic. High and Low never work, but I typically get intermittent when in the High position. Sometimes get intermittent in that position, but not always. Have replaced both front wiper relays and the multifunction switch (turn signal + wiper on steering column). I searched for a "wiper control board" (circuit board) like my GMC pickup has, but couldn't find any such thing. Looks like that may be handled by the Generic Electronic Control (GEM) module. Is this correct, or is there something else I should check? If it's the GEM, what's a good source to have it fixed?

 

[donalds]

Generic Electronic Control (GEM) module. Is this correct,

Yes

is there something else I should check? If it's the GEM, what's a good source to have it fixed?

Check your wiring

 

[dbcreed]

Yes


Check your wiring

Check wiring in any particular place? I've confirmed all the wires & plugs to the GEM look good and undisturbed (stock radio, no rust or corrosion around the module). What other wiring could be suspect?

 

[J_C]

Did you get a really good look at the MFS connector when you replaced it? Sometimes the contacts can push out the back of it, common fix is secure them in place from the back with hot glue or epoxy. I mean the mating wiring harness connector, not the MFS itself.

I'd also wonder about the wiper motor, would run a fused jumper wire from battery + to wiper contact #4 (low speed, white wire) then try #5 (high, dark blue/orange wire). You do not need your MFS set to have the wipers on for this, they would run continuously in low and high mode.

If wipers run fine in both those speed with the jumper wire, next thing to try is shorting the wiper run relay, pin 2, yellow/white wire to ground. If more convenient you can unplug the connector from the GEM where it's connector position 19 (still yellow/white wire), then with that shorted to ground, and ignition switch in run or accessory, the wiper run relay should trigger and the motor will run at low speed. If it does not, I'd suspect your GEM and get a pull from a junkyard, or open it and look for failures, or possibly before going to this much trouble, use a multimeter and measure for resistance on the following wires (see attachment below), all should be under ~5 ohms or so. If not, it's a sign of a wiring or connector fault.

1) Wiper Run Relay #2 (yellow/white) to GEM #19 (yellow/white)
2) GEM #21 (gray/red) to MFS (gray/red)
3) GEM #22 (pink/yellow) to MFS (pink/yellow)

Also pay extra attention to the MFS mating connector pins for #2 & #3 listed above, if they got pushed backwards in the connector as mentioned in my first sentence in this post.

Also there are those two large wiring harness connectors in the engine bay, that you might unplug, inspect, and replug.

2nd gen issues? Try this first!

Sometimes a gremlin can be caused by the smallest thing. There are 2 large wire bundle connectors on the firewall. Both are held tight with a 10mm bolt. Any bad connection in either plug can cause just about any issue. from bad transmission shifting, bad o2 sensor readings, no start, no...

www.explorerforum.com

Something else you can do is use a multimeter to measure for 12V on the motor #4 or #5 wire harness connector pin to see if it's getting steady power when acting erratic/intermittent. When it acts intermittent, does it seem like it is waiting the same precise amount of time to sweep the blades again, or does it vary? Does this change when the vehicle is parked, opposed to being subject to road vibrations while driving?

Wiring diagram attached.

 

[dbcreed]

J_C, thank you so much for your thorough and helpful reply and diagram. I didn't notice anything on the multifunction switch pins, but I did not look that closely. I will check that as it's not too tough to get back in there.

When it is acting intermittent, it is indeed waiting the same amount of time to sweep the blades consistently. This only works in "High."

I will check things as you said and report back.

 

[J_C]

I have just edited my prior post so it has more and clarified info. Heh, anything I write that's more than a few sentences, may be subject to later editing for a while.

Since the wipers are waiting same amount of time in high mode, next thing I would check among what I mentioned previously, is if the behavior changes shorting the wiper run relay #2 yellow/white to ground, then focus more on GEM itself and the wires to it that I listed. I'd also check resistance between MFS pink/yellow wire and ground, with MFS set to high, with the connector plugged into the MFS, and of course ignition on run or accessory. It should be very near 0 ohms (Ford often states "under 5 ohms" for something like this where it should approach zero).

Edit: I'm not 100% certain about this last part, if this should be near 0 ohms to ground. Maybe instead check resistance at the GEM wiring connector, between the GEM #21 gray/red wire and the GEM #22 pink/yellow wire. That should definitely be near 0 ohms with the MFS in high speed setting. This is with power (ignition) off, not running the wipers.

 

[dbcreed]

J_C, I followed your advice / diagnostic process as stated. Got all the way through to confirming that it was a bad GEM. Found a used GEM (perfect match, which I know is required) for $18 plus $10 shipping on eBay. It arrived, I installed it (helpful video at ) and everything - wipers and all other functions I understand are controlled by the GEM - are working fine. I do appreciate your help!