Questions and Answers

Ford F-150 Has Some Hot Wires Q. Greetings; I saw the tester with the fuse, lamp socket and wires and I built it. When I plug it into the fuse box the light does not come on, so of course I'm wondering how I could screw up something so simple. What might I be doing wrong?

I used a 1156 single wire lamp socket, two wires and a blown blade fuse. One wire I soldered to the wire of the lamp socket, the other wire I soldered to the metal lamp housing. I then soldered the two wires to the fuse, one on each blade. Each of my wires are about six feet long. I plug it in and no light, but if I ground it to the body, the light comes on.

My truck is a 1985 Ford F-150 with a 351W. The wire returning from the B+ on the alternator comes to a connector that splits this wire into three wires going to the solenoid, voltage regulator and... ?

One of the wires goes the positive pole on the starting solenoid. It decided to start overheating this wire and burning it out. I think from the wiring diagram this wire should be a red fusible link, but someone replaced it with a plain wire. I've been told that I have a short. No fuses are blowing, everything seems to work as before except this wire now overheats. I'm lost. Got any ideas?

Thanks;
John in Layton

A. You did nothing wrong. From what you describe it is working exactly as it should. If the circuit you are plugging the tester into has power and ground, it will light. I use it for locating a short in a circuit. I install it into the circuit that is blowing fuses and then start unplugging the devices feeding off that fuse.

If the light remains on when everything is unplugged, I grab my trusty wiring diagrams and, starting from the fuse box and working out, start unplugging and re-plugging harness joint connectors until the light goes out. Then I know the short is within the last section or wiring.

Now since you have a fusible link problem, you may need to make a similar tester using a sealed beam headlight bulb, not the new style halogen light bulbs.

The wire from the B+ of the alternator goes to the voltage regulator and through Fuse Link 'D' to the battery. So this wire is hot all the time. The size of Fuse Link 'D' depends on the alternator. For a 70 amp alternator it should be 14 gauge and with a 40 or 60 amp alternator it should be 16 gauge.

An 18 gauge fusible link would be red and a 16 gauge fusible link would be orange.

Power goes from the battery to the starter solenoid, through fuse link 'D' to the 'A' terminal of the voltage regulator and to the B+ of the alternator.

If this wire, that should be a fusible link, is getting hot, either something is drawing too much current, the alternator is overcharging or is shorted internally. Or it may be the wire is too small to carry the current efficiently, although I suspect the problem was there before and someone just stuck a plain wire to bypass the problem.

At this point I would check the charging system to see what the alternator is putting out. If it is overcharging it will need to be replaced. A couple of other things to check is the noise suppression capacitor connected to the 'A' terminal of the voltage regulator and the engine grounds from the engine to the frame and from the frame to the battery. You can make some temporary new grounds from household electrical cord and some solderless wire terminals