I am having an electrical problem with my 1999 F-250SD Supercab/Powerstroke.

When the key is in the off position and key is out, the radio and wipers still go, they never did in the past! This drains the battery and kills them in about 2 days.

When the truck is running, it runs and shifts normal but the overdrive switch on the shifter blinks but does not effect the opperation of the transmission and operated when depressed to engage and disengage the overdrive. The light keeps blinking!

At the start of all this as well, I am experiencing my spedometer acting erratic!
Whe going 30, the spedometer jumps all over from 30 to 60 then to 20, very smoothly I migh add. When you get the truck up to 55 or so the spedometer acts the same as it did as when going 30!

I checked and cleaned the battery terminals and the batteries are both about 4 months old. At the time of battery replacement the system was also checked because of different electrical problems prior to replacement which went away after replacing the batteries mysteriously! That episode involved the horn blowing as if someone was inside tooting it as if the alarm was going of... My alarm system in this truck does not use the horn! It has its own siren type horn.

I was told that the problem could possibly be with the ignition switch or if this model uses one, the Body Control Module (BCM), Have not looked into either yet! was trying to locate where these two components were located prior to posting this post with no luck as of now!

If anyone could possibly help, even to locate these components mentioned, I would greatly appreciate it!

 

Welcome to the site.!

Sounds like you may have a water issue somewhere. Leaky winshields will cause water to hit under the dash at various bad spots which can cause what you mentioned. Also a bad speed sensor in the rear diff might be your speedo and OD light issue. Easy to change And under $30. Has it been raining where you are??

Dick

 

Thanks for your reply! A mechanic friend of mine said the same thing as you did about the rain and YES, both incodents happened when it was raining or wet out. He thought it all might be related to the GEM module so I figured I would go further and ask on this forum. The speedometer issue also happened at the same time so possibly thought the speedometer ran through the GEM module as well. Does anyone know what this GEM module looks like and its exact location? I was told it is under the hood near the big master fuses somewhere and probably in line with the hood seal and maybe the culprit to getting wet opposed to the windshield leaking. Will be checking on all of this some time today when I get home later...
Thanks again for all of your replyies!

 

Gem module behind the fuse box inside the truck.. Get the windshield replaced that usually fixes the problem...Also when it dries out it should be fine hopefully.


Dick

 

Well, the weather dried out and the truck is back to normal, even the speedometer! This tells me that I guess the GEM module (or simlar?) is associated in some way with the Wipers, Radio, Windows, Overdrive light blink (Just the light, the problem did not effect the shifting or running of the truck!), and the Speedometer jumping eraticlly that I was experiencing. I searched all over in the spots I was told to look but I don't think I found where the GEM box is... Does anyone know where on the web I can look at a picture of one??? This may help me greatly in locating this box! I may have had my hand on it several times but if you don't know what it looks like it makes it harder! Also, does anyone know what these things cost? My winshield does not show ANY of the signs of leaking and there is not even dampness inside the vehicle. I plan on putting a piece of shower liner material over the top side of the new unit kinda like a tent to protect it as much as I can but the sure thing is, I can't afford a NEW WINDSHIELD! If I found Exactly where this unit it and it is definitely where the problem lies then I can look harder in that area to see if the winshield is leaking and dripping on this thing and try sealing it instead of replacement. Thanks again for the posts, they help, as does this site!

 

OK... After doing further searching on this site I now know where the GEM Module is located, thanks to everyone on this thing! The other part is still out there to my problems though... Is the GEM Module my problem? and how much do these things cost? Also reading I notice the "PCM" mentioned which is located under the brake booster and held with a 10mm nut... What does this device do and what does PCM stand for? Could this be my problem I'm wondering.... I'm trying to hit on everything so I don't have to go out and make Ford richer than they already are if I can help it! Are these parts also available at an auto parts store like Advanced or NAPA? Thanks again to all of you for your input!

 

Dealer only.. Gem is behind the fuse box. I paid $200 for a windshield installed.
Good luck.



Dick