So I posted up the other day that my alternator took a ลลลล on me. I'm now not entirely positive that that was the case. When I lost power, the only light that was on was the charge light, not the brake light as seems to be the case with genuinely bad alternators. All my gauges lost power except the speedo (mechanical).

Today I replaced the alternator with a Napa Gold reman. Truck starts fine, but I'm still only picking up 12.7 volts between the battery terminals, even with RPM's above idle. The entire gauge cluster does nothing. The charge light is off, but I'm almost afraid that that's part of what's wrong with the cluster and would be on if all was working. I can't roll down my rear window either.

I did find a small place on the alternator harness where the ground wire had rubbed through. It's got e-tape on it now, but I'm wondering if it might have shorted something out.

What are some more things that I can check?

 

Checked fuses right?
And you just said you got the ground fixed...
Maybe a wire somehwere leading to the gauge cluste came loose?

just throwing out some ideas...

 

cheak to see if there is a circuit breaker on that truck. it should be a small relay looking thing by the fuse box and it says circuit breaker may even have yellow on it

 

Check the guage fuse.

 

Be nice to know a few currents at various points such as into the battery from the alternator etc.

In the absence of that, I'm wondering about excess current loads, not enough to blow a fuse, but enough to be a heavy load on the system. I'd be tempted to pull the fuse for the rear window for instance.

Doesn't explain the gauge question. Need more clues here..

 

Saw those earlier, neither were popped.

If there is one, it's hidden and not documented 'cuz I couldn't find any fuses relevant to the cluster.

How would I go about checking those other points? I have a basic meter but I'm not that great with it as far as knowing what to test. Would the rear window have a constant load on it?

 

If the motor were engaged, it would draw a lot of current, and maybe not enough to blow the fuse. Probably not likely, as you would eventually blow the fuse.

As to how to measure current, basically you need to put a meter (and leads) that will take 20 amps at least, in series with the current path you want to measure. A lot of trouble if you don't have any stronger clues.

Need more info. Did this situation happen suddenly, all at the same time?

When you first turn the key on, before starting, what lights do show on the instrument panel?

Anyone know if the voltage regulator on our trucks is within the alternator?

I'm assuming you checked all of the fuses of course. So the instrument panel is the puzzling clue.

 

Yeah, fuses are good.

When I turn the key before starting, there are no lights at all on the instrument panel, not even the charge light. What happened a couple nights ago was I was turning into my neighborhood when all my gauges died. Still had headlights and dash lights, just none of the gauges worked. The only light showing was the Charge light, and from what I've read a bad alternator will also trigger the E-brake light at the same time. Once the truck is running, the cluster remains dead with no action or lights, and the rear window won't roll down.

I wish I knew this truck like I do my Mustang.....

 

Its deffinatly got a cluster fuse!!!! It may be labeled somthing like {Aux}lilary 1,2..... And always recheck the known problem. That wire you repaired could be your prob...

Next- Your alt @ idle 12.4 may be normal, pull your throuttle cable till it sounds over 2000 ish... you should read somthing more like 13.5+... Hope this helps!

 

I'll have to double-check the fuse. Makes sense there would be one, I just haven't found it yet.

Pretty sure it didn't change from 12.7v with RPMs, but I'll try it again tomorrow.

 

Found the problem. I don't function well on little sleep, and I've had 13 hours of sleep in the last 84, so I crashed for about 9 hours last night and when I woke up I felt clearheaded. Pulled out the old Chilton's manual and looked at the wiring diagram for my truck (or for an '87, since they don't have an '86 in the book). I recall that the red wire in the alternator harness was the one that had had insulation rubbed off by the ground wire. This ground, btw, attaches to the head behind the power steering pump and runs all the way into a harness on the driver's side inner fender. I have no idea what it goes to though. Anyway, it had rubbed through the insulation on the red wire in the alt. harness, which apparently shorted the red wire to ground. According to the wiring diagram, the red wire goes to the Engine fuse in the interior fuse panel. I had checked fuses yesterday, but only ones that seemed like they might be relevant. Pulled the Engine fuse out this morning and sure enough, it was blown. Tossed a new 15A in and fired her up, and not a problem. Checked voltage across the battery terminals while running and it was about 14.4 or so.

I'm not sure now that I even had to replace my alternator, but I already turned in the core. Got a lifetime warranty Napa Premium for the price of a 3yr warranteed one because the lower one was clocked wrong for my plugs, so I guess that's peace of mind that I won't have to change the alternator anytime soon. Now I just need to fix my leaking fuel pulse dampener, leaking upper radiator hose and the 5" crack in my downpipe and I'll be set.

Thanks for all the suggestions guys, I appreciate it.

Cliff notes: Get sleep, think clearly, check all fuses.

 

Congrats!

Does your rear window work now?

 

Good question, lemme check.

 

Yep, it works.

 

Did you lose your turn signals too? I've got an 88 4Runner with a very similar problem. I visited the carwash and halfway home (2 miles) my charge light comes on...dead instrument panel except for speedo, rear window won't go down AND no turn signal function.

It's been cold and everything has been ice covered and I have not checked anything on it yet (I know...I'm a wussie). Before the ice storm I did have an auto parts store check the alternator output while running at idle...30 amps. I went online and ordered a HO output alternator and a Red Top battery because it was on my to do list anyway. It sounds like I still have some work ahead of me.

 

I don't remember but I might've. Pretty sure I lost most everything that doesn't come on with the lights.

Get it into the garage, heated if possible (makes it a LOT more fun), and get under the hood with a good light. Just look for stuff that doesn't look quite right; even if you don't immediately find the problem, you'll gain some familiarity with your engine bay.