Unless you want the two days at the airport to be a test, be sure to disconnect the battery, or at least pull the blower relay, before getting on your plane. That way you can be sure that you will not get stranded at the airport. Finish troubleshooting problem once you are back at home. Hope you have a safe trip.

 

Mine is doing it now. I came out from work shut the door and the blower is running. Dead battery & won't start. I called a Ford Dealer and they said it's a JEM Module? Now I need to know where & what it is. I stop at the dealership tomorrow.

 

Resolution!
It was indeed a windshield leak. Relatively invisible until we removed the interior trim and vigorously sprayed the windshield. That dang water doesn't stain the headliner at all, but drained all the way across the top of the windshield, found a way to run down the channel in the driver's side A-pillar (structural metal support), and drips down on the GEM and fuse box near the driver's knees. My driveway is about 15 degree angle, and I was nose-down during the diagnosis. I don't know if that makes any difference at all, but perhaps something to consider.
Almost impossible to see the tiny water staining under the dash! Dried it all out, resealed the windshield, appears to be fine. (Did not replace the GEM nor fuse box). Amazingly, just the melting snow on the cab (when truck was parked - not driven) was enough to get it wet last time!
Thanks for everyone for posting here, and sorry I ever doubted the previous proposals to check the windshield first! This resolution also posted on another thread on this website!

 

My fusebox problem was not the windshield leaking,I had that changed. I found that the weatherstripping at the curve of the front of the door opening was pulled away from the body of the doorway just enough to allow water to run directly around the front corner post and into the fusebox. I hope this helps and that you haven't needlessly changed your windshield also. Good Luck. frank

 

I now have the same issue. 1999 F350 with 7.3 engine. How long does it take for the GEM to dry out? It has been doing this for 3 days. I remove the fan relay when I get where I am going.

My speedometer is also intermittent and the Overdrive off light is flashing off. The transmission does shift into overdrive though. And I can turn overdrive off with the switch and the transmission will not shift to overdrive, but the light continues to flash. When it is working properly it is lit constantly when overdrive is off.

I have the windshield leak too...but I am going to have it taken out and reinstalled.

 

It's the GEM not JEM module. It's located on the backside of the fuse panel.

 

That is exactly what my 2000 F250 7.3 is doing. I have just relocated from a very dry climate to a west coast wet climate. I guess the trick is getting it dried out and keeping it dried out. Thanks for all that, I'll let you know how it goes.

 

I put a small fan forced electiric heater in the cab directed towards the Fuses and GEM overnight and this morning everything was back to normal. Although I still haven't found or fixed the leak. Thanks for all that, saved me a bundle.

 

I am in the habit of turning the fan switch off before shutting the engine off.
This keeps from having an unnecessary draw, while starting.
May be relevant.

 

The FAN doesn't have an "OFF" position, only speeds 1-4.

The fan doesn't operate when the ignition switch is in the START position on most Fords, only in the RUN position.

Your extra efforts are not doing anything productive that you thought they might be.

 

My E-350 has an off position, for the features that are used.
I turn all fans, in all vehicles off before shutting them off.
Might also help keep them from sticking in just one position.

 

Okay, you have the E-series van with the aux rear climate control that does have OFF positions. Still doesn't matter. None of the blowers will run anyway in the START position. They re designed to only get operating power enabled when the ignition switch is in the RUN position.

In any event, it's irrelevant to this thread which is a discussion about problems related to water intrusion into the GEM module and fuse panel.

 

Mine has an off position..I turned it off rather than pulling the fuse.

 

Sign me up for this problem. I am wondering if there is a delay circuit that is powering up the blower motor. Mine was off and I got in the truck key in hand and the blower turned on. ? I started the truck turned switch to off and blower stopped, shut down truck pulled key blower started up.


Can't be relay if I can turn the blower off with engine running.


I pulled blower relay from PDM and verified the primary pins that energize the coil do have power key off and switch off. So the relay is doing what it is suppose to do when power is applied. The question is where is this power to energize the coil coming from and why?


Everyone talks about leaks. No rain and my truck is under cover and hasn't been rained on except for windshield washer.


My wiring info won't run on W7 only XP and that computer is history.


This problem sounds very similar across the board. Somehow the blower relay primary side is getting enough power to engage the blower fan.


Something may be back feeding the blower. Bottom line is dead batteries while away from home an a 7.3 with dual batteries is a real problem


Any help appreciated. I have no diagrams and hopefully will in next two weeks.

 

I'm not trying to cut in on someone else thread, but hopefully just add information and possibly get some help