Sound like a Bad GEM/BCM or Bad Grounds to you?

[Brandon96]

Hey all,

Just got my truck started back up and running after 3 years of sitting around. 1996 4.0L OHV V6 Vin code "X". Addressed all the fluids and replaced some vacuum lines that dry-rotted and she seems to be running great. I just got left with some what seem to be electrical gremlins that are starting to pain me..

Before I blew the flywheel up the truck was running great and had no DTC's or any issues of the sort. I do, however, distinctively remember losing just the 4-5 interval wiper speeds randomly for the couple months leading up to it. The Low Constant and High Constant (whatever they are properly called) settings on the wiper stalk worked fine.. except the blades would never return to the down position. They would just stop right in the middle of wherever I turned the wipers off. Fast forward to today, that problem still exists and the only difference is that the interval speeds just don't seem to work at all anymore.

I have noticed a few other issues;

1) The dashboard illumination lights - Speedo, HVAC controls, 4x4 knob, rear wiper etc etc.. will sometimes not come on when I turn the headlights on. The dome lights and door lights do however continue to work when this happens. Turning the headlights on and off a couple times or turning the truck off and back on seems to clear this up.

2) I accidentally turned the hazard lights on while cleaning out the dash and noticed only the left side of my truck was blinking. Only the left arrow and indeed left turn signals were flashing. I again turned them on/off a few times and turned the key off/on a few times and the problem went away. I still think the right arrow on the instrument cluster is out or not working.. not sure if that's a bulb but I currently have it ripped out to replace all the bulbs in it anyway.

3) The truck doesn't seem to want to go into 4x4 while in park when I use the knob. I can drop it into neutral and come back to park and eventually it will make its way to 4x4.

4) I have a DTC P1451 - "EVAP Control System Canister Vent Solenoid Circuit Malfunction". I have briefly searched the truck for shorts and tested that circuit for voltage, I can't say whether it's getting the proper voltage or not, I need to do some more research on that..


I'm wondering if anyone with any experience can offer up some advice. My thoughts are; Some of these circuits are not grounded correctly anymore or are not receiving proper voltage because of the truck sitting for so long OR, most of the circuits are connected/controlled by the GEM/BCM and it might be going bad.

This is just what I've noticed so far, but if anyone had any suggestions on how to go about testing/fixing any of these issues I am ALL ears. Anyone with any knowledge of the truck's electrical layout please chime in, I'm trying to track down some wiring diagrams. I'll be slowly picking at these issues over the next few evenings and weekends. I want to get this thing back out on the trails ASAP.

Thanks!

 

[96Green]

The hazard lights and wipers sound to me like a bad multifunction switch.
The multifunction switch is the stalk on the left side that controls the turn signals, wipers, and high beams. A new one is fairly inexpensive, and it's easy to fit yourself. I had similar issues in my Sport (the hazards only working on one side sounds very familiar) until I replaced it's multifunction switch.

 

[VR4]

The wiper issue is likely the motor itself. Bad park switch. The lighting stuff is probably switches. They tend to fail when left sitting.

Evap could be a solenoid or wiring

 

[Brandon96]

Update -

Replaced the multifunction switch, light switch and dimmer switch because of how cheap they all are on Amazon.. While I had the dash apart I took the speedo out, fixed the broken odometer worm gear and replaced ALL the bulbs (23 to be exact, minus the theft light) and got it all back together.

Got my wipers back to normal, and my turn signals seem to be alright. The arrows on the dash seem to both work as well now, not sure if that was a burnt out bulb or what, I just went ahead and replaced everything.

I'm still missing my backlighting for the entire dash, except for the first 1/2 second I turn the lights on. The dash lights up for a split second, then brightens all the way up and abruptly turns off. Also all the warning indicators are varying in brightness... For example the Door Ajar, Check gauge, Check Engine lights seem to be very dim at times while the others like 4x4 Hi and Low as well as the Turn Signal indicators are at full brightness. I can flick the headlights on/off and the issue clears. .....weird.

I also cleaned the EVAP solenoid, which was nice and crusty, and put it back in.. the code seems to still come and go. I think I'll just replace it soon assuming it's bad.

Does anyone know where the dash circuit is grounded? I'm sifting through the dash cleaning / reterminating the existing grounds.

 

[toypaseo]

I wonder if your dimmer switch is somehow bad/dirty causing the varying brightness issues...

 

[Brandon96]

Another Update -

The EVAP Solenoid needed to be replaced. I tried cleaning it multiple times, after voltage tested out fine two or three times and it still throwing codes, I sucked it up and put in a new one and whadoyah know,.. works great.

As for the instrument cluster, the ****storm continues.. It appears it's still wanting to turn off as soon as it "Warms Up" if you will. I have replaced the dimmer switch twice now, once with a reman Ford part and once with a Dorman replacement. The dash lights continue flicker or turn off as soon as they can.

I HAVE noticed that I can ALWAYS get the dash lights to come on if I first turn the headlights off, lower the dimmer switch all the way down, and then turn the headlights/parklights on. I can slowly bring the brightness up on the switch until what I think to be about 40-50%. As soon as they hit a certain percentage they either begin to flicker and turn off, or hit full brightness then abruptly turn off. I noticed the Reman unit would sometimes get extremely hot, actually too hot to touch and did note a little smoke rolling out from inside it. So, I went ahead and picked up another one which does not get hot like the Reman, but does the same thing the other two do.

I can post a video of the issue if it pleases the class, but I am completely at a loss and open to suggestions. I need some help here

What I've done -

- Replaced the multifunction switch with a Dorman
- Replaced the Light Switch with a new Motorcraft unit
- Replaced the Dimmer Switch with a Reman and then a Dorman
- Replaced any fuses associated
- Investigated, tried to associate some type of white movement with the 'blackout' but it appears nothing there is linked

So far the Issue has stayed the same and not improved.

 

[98 MERC]

Do think a relay is going bad and clicking off when the lights get bright ? Like maybe a relay is over heating or shorting out and turning off ? It almost reminds me of a circuit breaker in a house that detects a short and clicks off till its reset.Maybe you should start cleaning grounds for the hell of it.

 

[Brandon96]

SOO.. The mystery has been solved. Just wanted to get back and let everyone know what I found.

After robbing the junkyard of 3 PCM's, 3 BCM's, 4 dimmer switches, 3 light switches, 2 instrument clusters and a fuse panel I found that my issue had ABSOLUTELY NOTHING to do with any of that.

The problem was with my aftermarket radio head unit's harness. I replaced my crappy factory head unit with a nicer Sony unit. I used a name-brand adaptor harness to connect my truck's factory harness to the new Sony harness. The issue was, the old factory radio would dim with the rest of the dash lights, the new Sony radio DOES NOT. Therefor two of the wires from the truck's side of the adaptor harness (orange and orange w/ black trace) did not have anything to splice into on the Sony's side. I thought taping them up and leaving them to sit freely behind the radio would be fine.

Wrong.

They must have been touching something or each other and grounding off thus shorting my dash lights out. I have a bottle of liquid electrical tape and dipped the end of each wire in to seal them up. Everything has worked great so far.