Hey all new to the site. Found it while trying to figure out a problem with my truck that has me baffled. I tried searching first but to no avail so hope I haven't just missed a post. I've got a 1979 Ranger F150 short box 4x4 with 351m. I recently had to replace the radiator after the top of the fan shroud hit the fan and exploded and went through the radiator. While I was at it I replaced the thermostat and housing which had a small crack. I also changed transmission fluid while I was at it. Here is the problem.... After I start and let the truck warm up when I put it in gear both the oil pressure and temp gauge start climbing to hot. At first I thought it was air in the system but after burping and all I noticed something else that is steering me elsewhere. When I go from park to reverse not only do the gauges climb but the FM radio powers off and on real quick and the dash lights dim and flicker. So now I'm thinking it's electrical but that's where I'm lost. What could have happened? I've moved it from park to reverse and through the gears several times to be sure I wasn't just seeing things and it still does it. Mainly when shifting from park to reverse. I unplugged the neutral safety switch while running and still does it. Either I've hit something while working or part of the shroud hit a wire when it exploded but I'd like to try and pinpoint whether it could be a ground or what. Thanks in advance.

 

Is your alternator charging?

 

Yes it is. It started last weekend then I had to go out of town for work last week and started right up today.

 

try unplugging the horseshoe connector at the bottom of the steering column (that goes up to the turn signal/hazard switch)...It's possible there are some bare wires that get shorted when the shift tube moves. also check under the hood at the bottom of the steering column to make sure no wires are tangled up in the shift linkage...

also, I assume you are depressing the brake pedal when shifting through the gears...is it possible it occurs by just pressing the brake pedal?

 

No change with horseshoe connector and nothing anywhere near steering column or shift linkage... And no not just with brake pedal.

 

it has to be magnetic trans fluid, when you put it in gear the fluid flowing through the cooler creates a weird electrical field, thus causing your issues! :-)

my dad had a '77 with a manual, when you pressed the clutch the temp gauge would rise...never did figure it out (but never really tried much)..


just focusing on the guages...the guages rise because of current flowing through them, so either the resistance to ground is decreasing or the voltage from the icvr is going higher than 5 volts for some reason...since you've eliminated the wiring inside the column and around the shift linkage, the problem may be being triggered by the lower rpm's when the truck is in gear..

or, is it possible you have a loose or broken motor mount, and the engine is moving enough to move some wiring? (longshot, just thinking out loud)

 

Along that same line when changing gears a ground is changing.
I would go thru them all.
You most likely have 1 from batt neg. to motor.
Do you have 1 from motor to frame?
How bout from motor or batt to the body? I would say this is the one with an issue.
If you don't have this one add one.
When at it add one from frame to bed to make sure it has a good ground for the lights, don't count on the bed bolts to ground the bed.
Dave ----

 

Thanks for the info. I'm going to go through all of them in the morning and see what I can find. When the shroud came apart it must have knocked a ground loose somewhere.

 

does the fuel gauge also move up along with the temp and oil pressure gauges?

 

Does the horn still work? Maybe disconnect it temporarily and try shifting again.
Not that I can see any way for it to have an electrical effect (yet) but it's next to the radiator and it's wire might have taken a hit during the fiberglass explosion. Since it's also connected to the steering column, I just thought might as well check it.

Everything is a long shot at this point. Until you find the obvious puzzle piece.

Paul

 

X2 on the body ground. Typically your battery's negative cable goes to the engine block in order to supply adequate current to the starter. But the body/cab and the accessories inside need a ground too. Typically Ford puts an uninsulated flat braided cable between the bellhousing (a bolt) and the firewall, where it's secured by a sheetmetal-ish screw. I suppose flying debrisses could've severed it.

My truck was missing this ground when I got it, and the only symptom I noticed was the starter running on sometimes after releasing the key - never did it again after adding the body ground. Often times, the weirdest electrical symptoms you'll ever see are caused by a missing body ground. Your FM radio switching on and off sounds like one of these gremlins.

Other negative side affects/symptoms of missing body grounds are accelerator and clutch cables with the cable welded to its sheath. The cable was the default ground and couldn't handle the current. Think someone here a couple weeks ago mentioned a brake line at the master cylinder heating up due to a missing ground-strap!!

 

And when you start to see those melted wires and cables, your big main ground cable to the engine has either come loose, or is failing!
I'm a big fan of big battery cables for our trucks too. Even though some little 6ga stuff worked adequately when new, I like to recommend at least 2ga if buying pre-made stuff at the store, or 1ga or 1/0 welding cable if you're going big and making your own.
No such thing as too many grounds. And almost no such thing as overkill when it comes to battery cables.

Paul

 

No the fuel gauge doesn't move

 

Thanks guys. As soon as I can get out today I'm going to check all of your suggestions. It's not only Easter and April Fools Day but also my Anniversary so I'm not sure I'll find the time to sneak out there today. Thanks again much appreciated and I will report my findings as soon as possible!

 

LOL, triple whammy! That makes rabbit totally out of the question for the anniversary dinner...