Danger Will Robinson!!! I detect a long post coming!!!


I haven't mentioned this before since I was afraid it was too technical for some of the members (who I will not mention).

Here's an almost foolproof way to check a circuit. Several fools I know have been able to use it successfully - including me. On the other hand, I haven't met all the fools in the world.

1. Grab your multimeter. If you don't have one, get one. They are less than $15 (Radio Shack #22-810) and a real life-saver if you are doing any kind of serious work on these trucks.

2. Make some 20 foot or longer leads for your meter - one red and one black. Don't worry about voltage drop in the long leads, you're going to measure voltage and the length won't matter. Radio Shack alligator clips #270-375 $3.49, Radio Shack wire #278-1221 (you need some red and black) $5.49 x 2, Radio Shack banana plugs #274-730 $2.59 (so you can plug your new leads into your meter.

3. Set your meter to read volts. Make sure the scale is set to read at least 14 V. Connect the banana plugs on your long lead wires to the meter.

4a. 6V positive ground systems - Connect the positive (red) test lead alligator clip to the battery positive terminal. You can connect to the battery cable clamp if you are SURE the cable has a good connection to the battery post.


4B. 12V negative ground systems - Connect the negative (black) test lead alligator clip to the battery negative terminal. You can connect to the battery cable clamp if you are SURE the cable has a good connection to the battery post.

NOTE: You don't have to worry about the second alligator clip contacting any metal or electrical components on your truck. The meter has a very high resistance, and nothing will happen if contact is made.

5. Use the second alligator clip to connect to various places in the circuit. For the no starter spin condition, connect the second alligator clip to the starter case as a first test of the circuit. For no headlights, connect the second alligator clip to the headlight ground wire (leave the headlight connected) as a first test of the circuit.

Now comes the good part. You can test your grounds, etc. under load with this setup! For example, connect the second alligator clip to the headlight ground. Set your meter in the cab where you can see it (see how the long leads come in handy). In a properly functioning system, the meter should read the system voltage (6 or 12 V) without the headlights on. Turn on the headlights. In a properly functioning system, the meter reading should dip slightly but should not go anywhere near zero.

- If the reading drops to near zero, you have a ground problem between the headlight ground and the grounded battery terminal (+ for 6V, - for 12V). Move the second alligator clip to the part of the truck that the headlight wire is connected to. Make sure you have a good contact and try the test again.

- If the reading does not drop to near zero, the problem lies between the headlight ground and the non-grounded battery terminal. Move the second alligator clip to the wire leading to the headlight. To get at the wire, remove the headlight connector and temporarily insert a short end of wire into the connector socket. Then reconnect the connector. MAKE SURE YOU DON'T LET THE WIRE YOU JUST ADDED CONTACT ANYTHING BUT YOUR ALLIGATOR CLIP!!! Make sure you have a good contact at the headlight connector and try the test again.

You can do the same thing for any other circuit such as the starter circuit. Connect the second alligator clip to the starter case. In a properly functioning system, the meter should read the system voltage (6 or 12 V) without the starter engaged. Engage the starter and watch the meter. In a properly functioning system, the meter reading should dip a bit. The amount depends on a number of things - but it should not drop anywhere near zero.

- If the reading drops to near zero, you have a ground problem between the starter case and the grounded battery terminal (+ for 6V, - for 12V). Move the second alligator clip to the ground wire between the engine and the frame. Make sure you have a good contact and try the test again.

- If the reading does not drop to near zero, the problem lies between the starter case and the non-grounded battery terminal. Move the second alligator clip to the starter electrical input stud.

By picking different points in the circuit, you can narrow it down to the exact component that's failing. For example, with the starter, if the voltage does not drop to zero with the second alligator clip connected to the starter input stud, you might move the second alligator clip to the output of the starter solenoid. If the voltage drops to zero there, the cable between the solenoid and the starter has a problem, or the connections for that cable are not clean or tight.

Give it a try. Not much to invest at less than $20, and it works like a charm.

 

You're the man George!!!!

 

Nice explaination George. I thought I was the only guy with 20' leads! Jag

 

Thanks, George. I printed that one out for the reference book. I wondered what that Multimeter was for.

 

Charging the battery seems to be working, I got the starter to crank pretty strong last night. I need to fiddle with the positive battery cable to get a better fit (now negative ground) and will try starting it tomorrow or Friday. Also, I'm using an alternator now, about 7 years old, but it may not be charging correctly either. Need to check that out.

 

It is the alternator or its parts/connections. Thats my bet an I'm stickin to it.

Also... if your battery cables do not fit correctly, break down and run to PepBoys, they have 1 gauge replacements. Only set you back about $15 for the pair.

 

Well, I got the truck running yesterday, but it sounds horrible, like it's only running on four cylinders or so...
So, tomorrow I hope to limp it around the block and have the local garage give it some sugar. There appears to be several things amiss here, and I'm getting way out of my knowledge base.

Thanks for the suggestions everyone, and thanks George for the multimeter tips! I have one of those, but the instructions are very sparse.

 

You probably just fouled some plugs running it handicapped from a failing alternator/generator.