Dash lights on - charge, oil, A/T temp, etc - a definitive fix?

[Tenzig Norgay]

Try banging on it with a hammer while its running, its a little electrical trick called the TOW tap. You may have slightly bump it or spilled something on it when doing the PS pump, just disconnecting the harness and torqueing the alternator while doing so could have caused it to act up. Something at rest likes to stay at rest, exspecialy that old. At least thats what Einstein told me. Hit it with a hammer

Oh yeah, my alt has been acting up for a year now. Last summer it was giving me the lights. It was good all winter, now its starting to act up again in the warmer temps. I think it takes a long time for them to die, and thats why there are so many different answers and solutions to the fix. My alt has been in there close to 18 years, I feel like I should take it out and shoot it instead of hitting it in the head once or twice a month

 

[IdahoDoug]

Well, I appreciate the input very much as electrical is my weakness. I have two choices here - take the alternator out and bring it to a shop where they may say it needs repair/rebuilding and then they won't check the wiring on the car associated with the alternator that I suspect. Or, leave it in the car and have them find out why it's not putting out which may include a fusible link or something. Neither approach is ideal. If it IS the alternator, either choice works out but they'll charge me to remove the unit from the truck which is I'm sure a couple hundred to remove/replace atop the rebuild. If it is NOT the alternator and I take the alternator out for them, I'm sure they'll still find something not up to spec and repair/rebuild it and then I'll put it in and the lights will still be on. If you're still with me, then you can relate to the "I can do any repair on my Cruiser myself but I need an expert and my abilities will impair this process as I fret over not benefitting from my abilities" frustration.

Basically, I'm loathe to do the "normal consumer" thing and write a check on a vehicle I'm so well informed on....

DougM

 

[IdahoDoug]

Hmm...liking the hammer blows. Will do it....

 

[Bryan062087]

I agree with you Doug. Has to be something that you did when replacing the PS pump. I cannot believe the alt would go bad short amount of time.

I would be sure battery is not bad. Try putting your battery in it?

Time to look at the wiring diagram for alternator etc?

 

[PHIL O]

your alternator died pretty quick after servicing the PS. did you by any chance interchange the positive and negative connections while putting everything back together?interchanging them even for a nanosecond will damage the alternator. specifically the diodes. but replacing the diodes is an easy fix.

 

[landtank]

you take out the brushes, measure their length, and they are either good or bad. Not real complicated.

The other possibilty is that the brush channels has some dust and debris in them stopping them from freely moving. I'd guess that this could have been CJ's issue.

 

[Tools R Us]

If you have the alt tested separately, then you know if it's working or not, before messing with the wiring, etc. You said the big wire at the alt has voltage, so the fusible is most likely good, it still could be cracked, blown enough to show voltage, but not transfer big amps, my test for this is to pull on it, if good should be solid, if broken will stretch.

 

[concretejungle]

The other possibilty is that the brush channels has some dust and debris in them stopping them from freely moving. I'd guess that this could have been CJ's issue.

perhaps, but i took that baby apart and cleaned it up very well with degreaser, hosed it out, brushed it out, vacuumed it out. Put it in, worked for a few days and dead! I just figured it was a pain to get out once, now twice..... didn't want to mess with it again.

Plus, i had that bracket from photoman i was dieing to use. That's my experience anyways.

 

[IdahoDoug]

I can see that the brushes are not long enough - about 2/3 gone. But logic dictates that the slow wear of a spring contact like that would not simply quit providing contact from one day to the next. You'd expect intermittent issues, bumpy roads to retract them briefly and such. When I cleaned them with brake cleaner I'd have expected the contact surfaces to be clean enough it would have good contact again for a week, a day or at least an hour which is why I did that. If it had worked I'd have been safe to predict that new contacts would fix the nonworking issue but there was no change. So, I'm 'safe' to assume it is not the contacts methinks. Not sure, but methinks.....

DougM

 

[landtank]

Doug, are friggin serious. The brushes aren't long enough, they need to be replaced.

 

[IdahoDoug]

Yeah, that wasn't written well. They're worn down, but still touching so by "not long enough" I meant they're wearing - sorry. When I replaced mine on the 93 at 150,000 they were about half worn out, his are about 2/3 worn out based on the marks on the brushes themselves. There's a Nippondenso symbol or something like it cast into the surface and I could see it with the dental mirror a few days ago when I looked.

It's going to an auto electrician tomorrow for diagnosis.

DougM

 

[IdahoDoug]

OK, so update. Put new brushes in the alternator. Rick's comment was prescient as the contact I could see was fine but the other one was woefully short when I pulled the brushes so I thought "sweet, that's the issue!". Checked all the connectors that attach to it with a multi meter to establish that they have 12v or switched 12V as the FSM indicates. They do. Started it up and no change - idiot lights are on.

So, put it on the charger overnight just in case the battery is now so low from driving it around that the voltage is keeping the lights on even after new brushes but I don't have much hope.... In fact, I'm starting to doubt the alternator is the problem at this point because failures besides the brushes must be fairly rare, eh?

Any additional input.

 

[Tenzig Norgay]

Lightly tap it with a hammer, maybe ten times while its running. It may not solve the problem, but maybe a quick well what the heck. The TOW tap!

I've only gotten the lights once this summer, maybe 5 or 6 times last summer. The alt is stock and has lasted 17 1/2 years, 295K. The lights came on for maybe 5 to 10 seconds after start up, sometimes longer. Three times now the banging has worked for those few occasions when the lights didn't go off after reving the engine or 30 seconds of driving.

 

[IdahoDoug]

Forgot to mention that I did the tap thing pretty hard, actually. Whacked it near the front directly on the thick aluminum body of the alternator and then on the side as far rearward (before getting to the relatively thin sheetmetal rear cover. Nothing.

Thanks.

DougM

 

[Ebag333]

Any additional input.

How did you test the battery in it? What about the fuseable links?

 

[IdahoDoug]

Battery was tested by driving the truck to an auto chain where they test it for free in the parking lot. They said the alt was also not putting out anything, so drove it home for him to start the process.

I tested the fusible links indirectly by confirming they're not blown since I get 12 volts on the alternator square connector when it's supposed to (one is switched with ignition, two get power through a fusible link). One more thing I'm going to do is pull and clean the positive battery terminal connecting rings - some of which lead to fusible links. These are the last connections to finish cleaning all related connections to the alternator. Then, out comes the alternator - already soaking PB blaster on the alt bolts.

I'm really bummed the new brushes did not fix it. Since one was worn more than the other I got excited (OK, no wood in the shorts, but brief euphoria and that strange desire to find someone to high five with) for a minute or two. Then the new OEM brush pack did not change a thing...

Whatcha thinkin Ebag - some fusible link pondering???

DougM

 

[Ebag333]

Whatcha thinkin Ebag - some fusible link pondering???

DougM

I seem to recall someone having a partially broken fusible link. It wasn't blown, but actually physically damaged. They experienced some weird issues due to it. (Can't find the post/thread, can't remember if it came up in discussion or on MUD. )

I don't think this is the case for you as you've tested it, but for $12.69 list ($9.52 smart shoppers discount) it might be worth throwing at it. Certainly couldn't hurt if they've never been replaced.

If I had two trucks (oh, wait, I do ) I'd be awful tempted to swap the alt from the working truck to the non-working truck. That'd tell you 100% for sure if it was the alt or something else....but it sounds to me like you've removed all other possibilities anyway.

Checked all the connectors that attach to it with a multi meter to establish that they have 12v or switched 12V as the FSM indicates. They do. Started it up and no change - idiot lights are on.

My '97 FSM shows 10 tests. I'm assuming you didn't check the front/rear bearings (as it's still on the truck), and I know you did already check the brush length. Did you check the slip rings? Looks like you can do that with it on the truck still.

There also looks to be a few electrical tests that require you to open it up.

I see you tested for power, what about resistance and ground (on the slip rings/rotor)?

 

[Photoman]

With your meter, do a quick test of the charging current with the motor rpm’s up from the “B” terminal to the motor ground. As long as the battery negative to motor is good this eliminates the fusible links and connections.
With the motor running put the meter on AC and test between the battery positive and battery negative. Any reading at all and there is a diode leaking/bad.
There could be a problem with the “L” wire or its circuit. This wire comes from the charging light. SPECULATION - I think this wire may provide the excite current for the alternator fields to get the alternator to start charging. Some alternators work this way. There can be a problem even if a bulb in the circuit is burned out, or a crack or bad connection in the dash circuit board. I tried to ask my alternator shop if this was the way these Denso’s worked but they were not open that day due to the economy.
Also, I was going to ask them specifically about these alternators for doing a full field test. This tests the regulator. There is a small round hole in the back of the alternator that a screwdriver or whatever is stuck in, shorting to the case of the alternator. This bypasses the regulator and causes the alternator to output is rating. I don’t have a stock alternator to check where this is located, since I gave mine to CruisinGa when he needed one. Maybe you can ask locally or someone else here may be familiar with the stock alternator and can tell you how to do this test.
An alternator shop can check the alternator and eliminate it from the speculation. If it is bad a few days ago in a PM I offered you a free stock replacement 78 amp Mean Green alternator with very low miles on. The offer still stands.

Bill

 

[IdahoDoug]

Photo,

True to your frequent kindnesses and excellent advice, I am again amazed. Thank you for the offer on the alternator. If it were MY truck I'd accept it over my preference for OEM stuff just to have the novelty of such largesse on my beloved Cruiser. We'll be getting a stocker from the dealership here ASAP as this issue has run its course on my time and it's time to throw money at it to fix it. I've got only a few minutes this morning to try a couple of your suggestions and I'm going to carefully clean the positive battery and fusible link connections just in case.

 

[Tools R Us]

I seem to recall someone having a partially broken fusible link. It wasn't blown, but actually physically damaged. They experienced some weird issues due to it. (Can't find the post/thread, can't remember if it came up in discussion or on MUD. ) ...

The simple test for this is to pull on the fusible link, if it's broken, the insulation will stretch or the link pull in half. A good link should be solid.