Cougar

It could depend on which side had the bad connection. If the bad connection was on the protected side, or load, then the voltage would show fine through the fuse test points but the load would be dead. Also, the tester would not be a significant load so even if the problem was on the battery side and the load not applied to the circuit it may look fine with the tester.

I assume you just grounded the battery sense lead to do this test.

The battery sense voltage changes as the battery does. When more load is applied to the battery and the voltage goes down, the field voltage will increase causing the alternator output to go up and compensate for the drop. If a problem happens internally to the alternator then the lead for the light goes toward a ground level and turns on the light. When things are normal, the light is not grounded through the alternator and it stays off. When the key is turned to the run position the light will turn on because the alternator is not charging. This is a good check for the proper operation of the light circuit. When the alternator was checked, I assume they had a good load tied to it while under test, producing a lot of current, and the output wasn't just floating. Reading your previous posts it seemed the regulator and field voltages were ok and the output was low. You may have to get this checked out while installed in the car by a pro, but it sounds to me that the alternator may be bad. If the alternator had a good load on it when it was tested then it appears there is still a problem in the vehicle.

Right on Rallyruss! You are correct. Without that light, you have no field voltage to the alternator. Not all systems do it this way I suppose but most do I believe.

Going by the print that Legacy777 gave us, it shows that the coil of the ignition relay is tied to the yellow alternator lead. The other end of the coil goes to ground. Since it appears that the coil is turned on when the alternator is connected, power has to be supplied to the coil from the alternator and we know that is happening. The relay may be under the dash near the steering column.

This is easy to do so I would go for it. Be sure to have the ignition turned off when you do this. Using a stock one from a scrap yard should be fine. I have never had one fail on me. Since the coil provides the high voltage for the plugs, a bad coil will cause the engine to shut down.

My manual for an '88 model shows power going to a green wire and to a blue/yellow wire. Not sure if yours will be the same but it may.

I knew that the light would turn on when you put it on your car. The question is.... if the light will turn on in your mother-in-law's car. I don't think it will supply the load of the light. I think your meter was just picking up a residule voltage. I have never had to look at this kind of problem before but I think we are on the right track. If the light turns on in the other car then I am wrong about the alternator being bad and we will have to look at another avenue for the trouble. The yellow wire should supply voltage too the alternator and not the other way. That is the way I understand it at least. I will feel pretty bad if this doesn't fix things and causes you extra work.

In order to prove the alternator is bad you may be able to do a little test. Try placing a test light probe between ground and the yellow lead of the alternator (don't use your meter for this test). Leave everything connected with the ignition off. I suspect the light will glow on your alternator and not on your mother-in-laws. If that is the case, you need a new alternator. You could be correct, that one of the diodes is shorted and not blocking the voltage to where it should be. I don't think it would be the MPFI diode because that one is forward biased with voltage coming from the alternator direction.

The smoke may be due to a bad PCV valve. Check the intake manifold gaskets also.

Check to see if you are getting voltage to the grid connections. If you are, then the grid has an open connection somewhere. If you don't have any voltage, you need to trace back the wiring and find the bad connection.

You could try it on the dimmer switch.

Lets face it. If that really was a Soob then it wouldn't be there; right? I saw that car on the national news last night. I thought is was a Soob also when I saw it. It was just a quick shot showing the rain problems.

Your best choice may be to just have it towed someplace you can work on it inside. I'm sure your weather isn't too good to work on it outside. Removing the brake line on the frozen wheel may release the brake.

Can you hear the pump run for a couple seconds when you turn the key to the run position? You may have to crank it first then try again. When you measured the voltage to the pump did you measure across the wires to the pump only and not to ground? If you didn't, then you need to do it that way.

Did you check with CCR about a rebuilt engine. Remember, you will have a new 36 month warranty with it. That is worth a lot. The same as a new car warranty. If something happens to a used engine 6 months or more down the road guess who pays for more repairs. This is the route I would go if I wanted to keep the car for at least 4 to 5 years. When you cost average it then the cost isn't so bad. You may be to get by with a used engine just fine but these engines can have problems, particularly head gasket problems. This is why I think having a warrantied engine is important. You don't want to go through this again.

Garner, I suspect that some of the diodes are bad in the alternator and that is why the voltage is low. Full output can't be produced if some are bad. If you had a O-scope you could look at the output waveform. The main output lead of the alternator is tied to the positive battery post. The other leads are tied to the battery indirectly. The voltage you saw was being backfed from one of the other leads you had connected to the alternator. That kind of test doesn't really mean much. The real test is having all the leads connected normally and checking each of the voltages then. They all should be over 12.7 volts with the engine running around 2k rpm. A new alternator should fix you up fine.

Your welcome for the help. Hopefully you can get another one. Keep us posted on the progress. I would use the same thread.

Well then, it does indeed sound like the alternator is backfeeding the voltage to the other things.

Ok. Lets pull fuse #16 and then see if you still have 12 volts on the yellow alternator lead. Make sure everything is hooked up normally except for the fuse.

Bruce, Ok, the alternator looks good. I was wrong. Lets see how the voltage is being backfed. What was the number of the ignition fuse you pulled and the lights went out? Edit: When you took the voltage readings was fuse #16 back in place or was it removed at the time? After rereading your previous posts it sounds like that was the fuse that killed the lights, correct? Another thought! Lets take an ohmmeter reading of the two small wires on the alternator but place the common meter lead to ground this time. You may want to disconnect the positive battery lead from the battery before you do this test. Maybe one of these leads is going to ground.

Since you have a multimeter handy lets do some testing. I would like to know what the voltage is on all the leads to the alternator, along with the colors of the leads, with the ignition off, and everything connected normally. Another test you can do is remove the alternator lead connections and set the meter to read ohms. Place the red probe lead of the meter, which should be connected to the + of the meter, and connect it to the output lead of the alternator where the white lead would normally tie to. Place the black lead of the meter to each of the other two small wire connection points on the alternator one at a time. Do you get a low ohm reading to either of the small wire connections from the output lead? If you do, then something is wrong in the alternator.

The noise may be being picked up by the antenna instead of the power lead. If the antenna ground is not good it will pick up excessive noise. If the noise sounds like a snapping noise then the ignition wires are probably causing this. Replacing the plug wires and coil lead may help fix this.

I owned an '88 GL-10 that had a fuel pump problem. The ECU controlled the ground lead connection to the pump. I found the problem in the ECU and replaced the bad transistor. I suspect that the pump on your vehicle may be controlled the same way. Hard to say the ECU may be bad though, it would be one of my last guesses really. I would suspect the lack of a signal from one of the engine sensors may be causing this. You may find a clue to this problem by checking the ECU codes. Check all the fuses also.

Ok Josh, thanks for the notice about that. I assume that there is still a main battery lead connection that is hot at all times (he refers to a white one). I am looking at this statement that Bruce makes: He states that the main lead "is not disconnected off the alternator", a different way of saying "when the lead is connected" in my thinking. Since things are fine with the alternator disconnected then it seems that it is problem. I believe voltage from the main lead is backfeeding through the alternator, to the other wires, and turning things on that shouldn't be until the ignition switch is turned to 'run'. I may be wrong, but I think this is what is happening. A simple ohmmeter test of the alternator leads would prove this out.