I ran my 97 F250 into a hole trying to run some cows back in the pasture and tore my front axle up, so while its being fixed I'm relying on my 88 F350. I charged the A/C, worked good, then all of a sudden today the truck runs bad hot, but cools down IMMEDIATELY when you turn the a/c off, like hit the button the gauge drops from maxed out to a little above halfway. The speedometer also quit working today out of nowhere, going down the road and it just quit. This is the truck with the gearvendors overdrive unit, and it won't shift if the speedometer doesn't work. Does anyone know enough about these gearvendors to know how the speedo works through them, I seem some kind of adaptor under there that plugs into the GearVendor, then the stock cable plugs into it. Right now though, I need the truck to not run hot. I just spent a pile of money rebuilding the engine in this truck, it has less than 1,000 miles on it, I don't need to go blowing it up again. I used to drive all the time with the a/c on, it has never run hot like this before, it boiled some of the water out today. I was wondering if you can overcharge the a/c on these trucks and cause the compressor to pull to hard? Or maybe something else? It should not run hot w/ just the a/c on.

 

fan clutch possibly? the ac makes a big difference on engine temp

 

How old is your rad? What about your thermostat (is it the correct OEM replacement)?

AC makes a difference, but it shouldn't be that drastic.

If it wasn't for your mention of the water boiling, I would be more enclined to lay blame on a faulty cluster gauge regulator.

 

I just put a fan clutch on it about a year ago, I hope its not bad again. As for the thermostat, when I had it rebuilt last year he put one in it, but I don't know where he got it, he probably just bought it at Napa, thats where he buys everything else. My radiator was leaking when I had the motor out, so I got one from a junkyard, don't know anything about it. Where should I get a thermostat?

EDIT: ALso when I drove home last night, when I turned the headlights on, the charge gauge moved a lot, lights on and off were moving it just like A/c was moving the temp gauge, and this is a brand new alternator. Do these trucks have an old fashioned voltage regulator, or something else?

 

The regulator of the alternator should be located on the passenger side inner fender.

Thermostats should only be purchased from ford or international. Generic thermostats that you get from autoparts chain stores are not the correct type and can cause overheating problems.

Heard of some that were able to get something from NAPA that works well, but I never tried it.

 

david, i go mine from oreillys, noproblems from it, but it is the correct shape, not the gasse style i took out of it.

 

I just got one from O'reillys, looked the same as the one that came out, but it had a different rubber seal than the one that was in it, and it wouldn't seal, I spent all that time trying to get it out and back in, and it leaks, so I pulled it all back and I'm gonna tell them they can stick that thing. So now, I'm going to Ford to get one. At least I got my other truck back so I have something to ride, but I still want this one fixed.

Is the silver metal box the voltage regulator?

 

Yep, that box is the regulator.