hi all,

so i've been browsing this forum since i got my 99 f250 last year (great forum btw ) and now i need some help.

It started last night, I was driving and the od light was flashing. Trans shifted normal and even went into over drive.

This morning I went to start the truck and it would not start, turned over but no go, I couldn't hear the GPR so i check under the hood and one battery neg terminal was loose, i tighten it and it fired right up. I drove and parked the truck and when i turned it off i noticed the blower motor was still on. I turn the **** to "off" and then back to the "face vent" and sometimes it stayed off (only on pos 1 on the blower motor) if i moved it to pos 4 it would come back on. I removed the radio, dash bezel and was checking the wires. I could hear the blue relay (turn signal relay) to the left of the radio clicking, i removed it but fan still came on. There are two small relays next to the blue one, anyone know what they are for?

At this time I also noticed that the battery light turned on and also the ABS. I have the Aux PCM, it always stays on and sometimes it showed "Error" on the screen. The battery light will stay on even when everything is off.
*EDIT* When i pressed on top of the GEM the battery light would get a little brighter and then dim again

I turned on the truck and not all the lights came on on the cluster, The WTS, or CEL and others didnt come on. When i went to turn it off it would not shut off. Key out, ignition off and the truck was still running. I had to pull the #15 fuse to turn it off.
When the truck is running with the key out the gauges on the dash were fluctuating on/off when i gave it gas. The rpm needle sometimes would turn off and then stay on.

Something is causing the relays to kick on and off. I hear the blue relay behind the radio buzz (i dunno why if this is only the turn signal relay).
The Aux pcm will also turn off and on along with the relays.
When the relays kick on, the fuel pump starts priming. All this happens when the engine is off and no key in the ignition.

I've been searching and came across the GEM Module, is there a way to testing this? Tomorrow i want to remove whatever i have to in order to check the wires to make sure one is not rubbing and grounding somewhere.

sorry for the long post but this is everything i wrote down as i was working on the truck. If there is any more info you need please let me know and i will give it as best i can.

Thanks in advance

 

I would start by pulling your battery terminals and clean and reinstall them, make sure their tight. also charge your batteries and mabe have them tested, low voltage/bad connections can sometimes cause wierd things. It does sort of sound like it could be your GEM. Windshield can leak and drip on it. It's attached to the back of your fuse panel.

 

I agree 100% about low voltage/bad connections can sometimes cause wierd things.

But it also makes me wonder if Green Terrace do you have a alarm, a/m radio or auto start system on your truck?? Because I have seen these kind of problems in the past when someone wires up these things with the wrong power leads tied into something.

 

Ok, mine just done the same thing with the heater running still. nothing else amiss.

I was thinking of the ignition switch acting improper.

E99 F350

 

The only vehicle I've seen still running with the key removed is my 73 F250 crewcab and it was the ignition switch so im interested in seeing what fixes your issue.

 

When i bought the truck last year the owner had installed two new batteries. One is definitely bad because i clean the negative terminal and in a weeks time i can see more build up (the white stuff). I can also see that the battery is leaking from one of the two caps that are on top. I'm looking for the receipt so i can go back to pep boys and get a warranty replacement.

This truck is the basic model. No power anything, no alarm and no remote start. It was a state truck and they had light beacons on it. It also has a Meyers plow and the Aux PCM.

One thing i forgot to mention too is that when i was checking the fuses with my test light, and when i checked fuse 19 i believe, the test light would turn on and the relays would kick on like mentioned on the OP.

Its just so weird because it was running good. I did a muffler delete and installed a new fuel filter with cap and also checked my CAC boots on the drivers side. I could hear the turbo and life was great until this. Any other help is greatly appriciated.

I'm going to tackle this beast in the morning and see if i can figure anything out.

On a side note, it had been raining here in NJ almost all week, so i will check the GEM for moisture inside.

 

One Bad battery will kill a good battery, if its wet it is shorted out inside

Rule of thumb: replace them both same time!

 

Good point, i will take both tomorrow

 

Me thinks you probably answered your question regarding the rain...
Dont be to quick to jump to a leaky windshield...
I believe this gremlin has many times gone misdiagnosed...
Took me sitting in my truck for an hour in a downpour to finally locate the source of the water.
The cab marker light lenses, and the fastening hole where the screw holds it in place...
The seam between the cab marker base, and the lense leak into the center of the assembly... then ... most dastardly... follows the almost perfect liquid path down the pigtail... drips off the loop onto a cupped roof support... and flows down the a pillar... from there... almost directly into the fuse box/gem by way of t h e main harness... like they planned for them to leak after x many years... its almos t too direct a path to water potentiality killing a truck for it to be coincidence... *xfiles music*

 

When you were checking fuses, were they the ones under the dash or in the engine bay? If they were under the dash, then fuse 19 is for the Auxiliary Powertrain Control Module (APCM), Instrument Cluster, GEM Module, Overdrive Cancel Switch, Idle Validation Switch, and Overhead Console.

It just so happens that fuse 15 under the dash is for the GEM module, PCM, Anti-Lock Brake System Module, Brake Shift Interlock, and Speed Control.

One thing that comes to mind is your GEM module had gotten wet and is causing issues with everything else tied into fuse 19 and 15. The only way to check the GEM is to replace it. The wiring to or from the GEM module could also be problematic. Check wires between fuses 15 and 19 and the GEM.

If you go to eBay, you can search for the part number of the GEM that's in your truck and find a used one or go onto car-part.com and do the same there. I've found 2 GEM modules for my truck on car-part.com for around $75 - $90.

Otherwise, you can do some extensive pinout testing starting from fuses 15 and 19 to each of the other components with the help of a wiring diagram.

Good Luck,
Drake

 

It was the fuses under the dash. I will check what you said tomorrow morning. I will also look into that website, i dont mind spending $90 even if that is not the problem, but $250+ would suck as seen on other sites. Anyone know what service manual is best for the 7.3 diesels? I want to invest in one because there are some relays that i have no idea what they do.

I will post my findings if any tomorrow!

thanks to all

 

*UPDATE*

I spent all day today and this is what i discovered.

I went to turn on the truck this morning and everything was working as usual, the only thing wrong was that the blower motor still turned on when the truck was completely off.

I ended up taking the GEM out and this is what i found

Two main connectors removed, you can see all the dirt build up and you can see the water residue






Removed the GEM and found more water residue and two droplets of water.





I opened it up and everything looked good except the dried water mark under the connector.



I took the board out and on the back side was this. I cleaned it with a soft bristle tooth brush and some electrical connection spray cleaner.







I cleaned everything with compressed air, the wire side connections as well and used dielectric grease. Put everything back together and truck worked flawlessly. I might get a replacement just for the heck of it (will the new-used one have to be re-flashed?). O/D light stopped flashing, truck turned off on a dime. The blower motor is also working like normal.

Thanks everyone for their help !

 

I also found some cut wires taped off.

Does anyone know where/what these wires do/go to?

This wire is Blue/Yellow, it is next to the plug for the Aux PCM.


The wire farthest to the left is Blue/Pink. These wires are tucked up above the accelerator pedal. They look to be coming off of the main harness and look to be cut off clean, are these for a trailer brake controller?


If you need any more pics please let me know!

 

Did you locate the source of the water? If it happened once......

And those do look like the wires fro the brake controller but I am not 100% sure,

 

The water is definitely coming from the pillar. I have to patch a small hole on the roof of the truck (it had a beacon light before) but that is right on the center so not sure if that would do it. I am going to double check the roof lights and make sure they have a good seal.