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Do I have a bad GEM?

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Old 12-03-2018, 10:55 AM
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Do I have a bad GEM?

In this thread https://www.ford-trucks.com/forums/1...oor-locks.html I learned that the GEM (generic electronic module) controls the power windows. Mine are randomly quitting, for a day or so, then they come back. 2000 F-250 XLT 7.3 (see sig).

Today I got another weird symptom. The Edge Insight console lit up when I opened the driver door! The Edge is only supposed to come on when the ignition is on. My master tech friend said broken insulation in the door hinge area could cause that, but we looked at the loom there and it looks great. No visible breaks and the rubber is still flexible.

I wonder if my GEM is going south, and it's monkeying up both the power windows and the Edge. We used the Edge to check codes, but it has no codes logged. I learned here that the GEM can get water in it in early Super Duty trucks because it's attached to the back of the fuse box, so Ford moved it in 2002 to a safer spot. We put a new windshield in this truck, so no leaks now, but perhaps it was leaking earlier.

Does the GEM have to be programmed to the truck when you put in a new one? I found a post on PowerstrokeNation where some poor guy replaced his GEM without flashing it into the truck, and his truck went wacky like a wolverine on meth. He'd switch on the ignition and the starter would engage immediately, for example.

Edge Insight II console:
 
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Old 12-03-2018, 04:03 PM
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Yes it is likely that the GEM is going bad as its chock full of relays. my 99 7.3 had a windshield leak water got there and it would also do weird things like turn on my defroster without the key in the ignition and try to start itself randomly. Definitely get it replaced before it causes shorts in wires and such and possibly start a fire. I replaced mine with the exact model code that was on it.
 
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Old 12-03-2018, 11:11 PM
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If you're only having power window issues I would definitely consider pulling the GEM and fuse box and seeing if there is moisture/corrosion inside, but I wouldn't automatically assume that the GEM is bad. Usually when they go bad, there are multiple symptoms, windshield wipers being another very common one.

If you end up needing to replace the GEM, you need to get one with the same code number printed on it or you'll have all kinds of issues.

Yes, the windshields on these trucks are well known for their leaks.
 
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Old 12-04-2018, 09:28 AM
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Thanks guys. We'll pull it and have a look. My master tech friend also wants me to reinspect the door wiring loop very closely at the door jamb side.
 
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Old 12-04-2018, 11:30 AM
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Originally Posted by RenoHuskerDu View Post
Thanks guys. We'll pull it and have a look. My master tech friend also wants me to reinspect the door wiring loop very closely at the door jamb side.
I would think if it's only window issues, that it's more than likely a bad wire in the loom, years of opening and closing the doors break wires. You have to inspect each wire closely, it may look good on the outside but could be broken on the inside, I went through the window issues on my 95 F250 and it was all in the drivers door
 
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Old 12-05-2018, 04:58 PM
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We got the fuse box, GEM, and computer out. No corrosion or traces of water infiltration. Unplugged and reseated the GEM a few times for good measure.

So the only remaining causes, logically, would be wires in the door jamb, a failing GEM, or Russian spies.
 
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Old 12-09-2018, 12:21 PM
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If you don't see water or corrosion, I think that basically seals the deal that you're looking at a wiring issue for the windows alone. Again, when the GEM goes bad, it usually takes a lot more than windows with it. And the general cause of them going bad is water infiltration. You don't have water infiltration. Look elsewhere.
 
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Old 12-09-2018, 09:30 PM
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Thanks guys.
We did a closer inspection of the wiring loom at the driver door. Both sides of the bellows come off easily and are flexible. The wires in there are also flexible and we didn't feel any variations in the feel of the wires that might reveal a broken wire inside the insulation.

In another thread I saw a mention that the power door lock switches daisy chain, such that just one bad switch can foul up locking for all doors. I already pulled, opened up, and inspected the driver door power lock switch. It could not look better, might have been replaced already. If the truck acts up again, I'll remove and disassemble the front passenger door lock switch.

If the problem doesn't come back, perhaps reseating the GEM connectors helped. They look like they are a copper alloy, with tinned connecting areas on the flat sides, and copper visible on the edges. Probably pretty spendy stuff.
 
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Old 12-10-2018, 01:01 PM
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Die-electric grease is your friend. And yes the power locks run off of each other, at least in the crew cab non keyless entry that I have. Threw me for a real loop last time I had the door panel removed.
 
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Old 12-10-2018, 01:20 PM
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I think my GEM has been bad for ages. I had the power lock problem, and solved it for awhile using the foil trick. Which might have toasted the GEM, I don't know. Eventually I replaced all the actuators with aftermarket ones that work much better. Some years ago they stopped working too. The aftermarket keyless alarm still works, but the doors never lock.

As I recall the GEM is buried in the dash, and expensive to replace. Which is why I've never bothered to fix it. I think the lock actuators are okay, they're just not getting input from the GEM.

Early '99, but I don't think I've ever had a windshield leak (?)
I'd like to fix it if it's a reasonable job.
c.
 
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Old 12-11-2018, 12:11 PM
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Again, just non-functional power locks dont mean much in the way of a bad GEM. Youd have many more problems than just the locks. Actuators in these trucks are junk. And the locks all feed off of each other. Id be willing to bet you have a bad lock switch somewhere.
 
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Old 12-11-2018, 03:38 PM
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I'm glad to hear that advice again. Only the door locks are acting up. This was a one-owner truck, and we don't get a heckova lot of rain in Texas, so our GEM has apparently never been wet.
 


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