The weather here has been very nice so today I decided I was going to wash my truck. When I went to go start it, the bulbs on my dash for the four wheel drive system and my dome light came on. Both of these things did not work beforehand so I was surprised to see them on. I was able to shift the truck into 4h and back to 2wd without any issues. But about 5 seconds after I was able to shift it, the lights went off and I was not able to do anything with the dome light or four-wheel drive again. I pulled fuse 25 and put it back in, and I also unplugged and replugged the general electric module. I previously replaced the double relay in the dash but that didn't change anything. I honestly have no clue what to think is the problem now. Help!

 

There are two dome light circuits
Door open circuit powers dome light via dome light relay operated by GEM
Dimmer wheel switch powers dome light directly, by-passing GEM

Door open circuit also activates Door Ajar light, along with dome relay, is door ajar light working?


Both 4WD lights should come on every time key is turned on, all status indicator lights in the dash should, its a BULB TEST, nothing to do with the system the bulb represents
After test, bulbs go off, usually a 3 to 5 second test

When you shift to 4high then GEM would turn on that 1 light, IF shift motor was in correct position, 4WD lights would flash if it wasn't in correct 4high position

If door jar light doesn't work, along with dome light, when EITHER door is opened
And the 4x4 system doesn't work reliably then its most likely a GEM issue, could be a loose connection in wiring at GEM

 

I have been able to replicate this by driving around with the heat on full blast. After about 20 minutes or so with the heat on, the dome lights and 4x4 work again. Everything else it does, like the wipers always work, so would this just mean that my GEM is shot and I should replace the whole thing?

 

I would pull the radio and have a look at the GEM connectors, could just be some poor connections for the pins and slots on effected systems
I have read of people opening up the GEMs and cleaning them with isopropyl alcohol and Q-tips and getting then working again, but............never tried that my self

But yes you can replace the GEM, 1998-2000 would be years that would work, needs to match 4x4 of course but also power windows if so equipped
There will be a part number on the GEM, if you can match that and the 4x4, power windows that would be best

 

I pulled it out and the connections looked fine, but I still sprayed it with some QD electronic cleaner and opened it up. Again, it looks fine to me (I'm no electrical genius) but I'll try cleaning it with some isopropyl alcohol. Ill attach some images of the circuit board below:

 

Yes, looks fine in my opinion, as well

I guess just clean it and plug it back in, see if it works

 

So I cleaned it and it worked... For a day. I cleaned the connectors and the circuit board then when I plugged it back in it all worked perfectly. I could put the truck in 4hi and low and use the dome lights. It then would work randomly for a few days and now I'm back to the same old stuff with it not working. Im going to give it one more quick cleaning. I'm guessing the next step would be (if that doesn't work again) just replacing the GEM?

If I were to do so, my truck doesn't have the power windows option, so would I need to find one without the power windows or would I be able to use one with it?

 

You should be able to use one with Power Group option, but never tried it myself, GEM just did the "one touch" up and down for the power windows, so shouldn't set any "B" codes if its not connected to window circuit

 

Thank you so much! My current GEM is a 1998 F87B-14B205-ED and I'm wondering if I could use a XL5T-14B205-EC GEM out of a '99 4x4 Ranger. They look the same and I know the 98-99 4x4 systems are the same. Would it be a viable replacement part?

 

Yes, that should work fine

1998-2000 GEM is programmed for factory tire size it came with so speedo can be a little off, but wouldn't be by much, the 4x4 Rangers only had 2 or 3 tires sizes and diameter wasn't that different

 

Thank you so much! I'll order a new one and we'll see how it goes!