DD Problem

[GMC1977]

Im havin a electrical problem with my 99 f150 ( i knowit was cheap). i noticed the reverse lights were not working the other day and now the AC compressor clutch wont engage. I looked at the fuse and it was good but the reverse lights, running lamps and AC clutch relay all run off of one circiut in the fuse box. Any ideas on where to start?

 

[Fordum]

Do the running lights work?

Probably two different problems. Backup lights are probably either bad bulbs or a bad transmission switch.
Ac clutch may be low on gas.

Low pressure switch is usually on the accumulator under the hood next to the firewall.
Two wires plug in. Turn on the AC, unplug the plug and jumper across them. If the compressor comes on, unjumper it and get the AC serviced to find the leak.

 

[GMC1977]

all of it went out at once... the AC and the reverse lights went out at the same time.

 

[Fordum]

Not real sure about that then.
Sure sounds like a main power problem. Did you try replacing the fuse? Sometimes you can get fooled.
I don't know of any reason that any control system would have the ability to control those two items.
Its going to take a schematic to figure it out, and I don't have one.

 

[GMC1977]

I put in a new fuse and a new AC clutch relay. No dice. No power at all to the pressure switch or lights. when i got the truck roughly a month ago EVERYTHING worked great. and i know the guy(my manager) i bought it from hadnt rigged anythin on it because it had been sittin on the back lot of my work for almost a year when he just went out and bought a new truck. Im thinkin either fusible link or short to ground.... But wouldnt a short pop the fuse?