I need help!

My son recently purchased a 1994 F150 4x4 from the local auction. This truck was an insurance writeoff and has been rebuilt. He managed to run the battery flat and when he and his buddy (not me!) jumped it, they reversed the jumper cables hooking the ground to the hot side of his battery. Needless to say there were a few sparks etc. Following this learning experience the truck seemed O.K. for a about a week.

Since then it's developed a number of electrical problems:
- The fuel gauge is erratic. Works sometimes, and not others.
- The speedo has quit and only works when he applies the brakes.
- No high beam without holding the lever back.

This sounds to me like a bad ground somewhere, or perhaps a toasted computer chip. I also thought perhaps he'd knocked a ground wire loose when he tried to fix the radio. This is the same truck that's mentioned in the thread "1994 F150 Radio Wiring", and there are a number of wires that seem to go nowhere.

Anyone have any thoughts.

Thanks

Rick

'03 F350 XLT SD Supercab dually, V10, auto, 3.73LS

 

karic,

1- Fuel Gauge - The fuel gauge can only fail in 2 places, at the pump/sender in the tank, which is fairly common, and at the instrument cluster itself.

2- Speedo - Again, it can only fail in two places, at the pickup on the top of the tranny (it's driven by a little gear) and at the instrument cluster.

The likely conclusion then is that he fried the dash cluster. I'd suggest you get a hold of a used one from a wrecker (they're all the same) and see if everything works as normal. If so problem solved. If not, try the other end of the problem, the speedo pick up and the fuel pumps. It may be the PCM, but not likely, and pricey.

As for the headlights, if the high beams work when held on, then it seems more like to be a faulty switch than a ground or electrical problem, otherwise the high beams wouldn't work at all.

None of these problems is nesessarily directly related to connecting the battery wrong, so I wouldn't rule out failures at the other end of the fuel and speedo gauges. I think we've all caused a short in one way or another before without causing any serious damage.

One word of warning that you may not want to hear, I had an 89 F250 that went through a fire in the shop, they refused to write it off but it got hot enough to do damage. I spent the next 2 years chasing small electrical problems in that truck and never could get it back to 100%. I eventually got sick of spending money on it and learned to live with its quirks.

Waxy

 

If the high beams are like mine, pulling back on the turn signal (toward the driver) is intended for temporary application of the high beams, i.e. flashing someone. Pushing forward on the turn signal (toward the dash) makes them stay on. Then, of course, pulling back to the middle position cancels them.

Hope that helps.

BTW - The other problems you mention seem to be common problems that are discussed here. Hopefully, they are just normal glitches found in these trucks, and don't indicate major problems caused by the polarity boo-boo.

Good luck.

 

mrwizard;

Yeah, same switch. But the high beams don't work when it's pushed forward.......only in the "flash to pass" mode. I think Waxy may have hit it suggesting it's the switch. It just seems weird that all this is happening at once.

Thanks for your input.

Rick

 

That multifunction switch (blinkers, wipers, hi-beams) CAN be disassembled and cleaned/repaired, but replacements are cheap. I think some parts stores sell them for less than $20.

The PSOM (speedo) has several inputs that could fail but it sounds like you need to check the Wh/Ppl wire from fuse 18 under the dash. It goes to a 6-way splice, one of which feeds the PSOM and another of which feeds the shift interlock on the side of the steering column That's the ONLY place the speedometer is interconnected to the brake switch, and there's a diode inside the shift interlock that may be bad, but there would also have to be a break in the W/P wire to the PSOM for it to have that effect.

The PSOM is independent of the other gauges in the cluster.