My alternator belt was slipping on my '98 Toyota Tacoma (V6). It started a few weeks ago. It squealed when I would start the truck, and then go away a few seconds later. The squealing progressively got worse. Then my dash battery indicator light came on and off intermittently. It would be on for anywhere from 1 second to a minute, and then turn off. When the indicator light came on, my headlights would get brighter, and the cabin fan speed would increase. Then when the battery indicator dash light would turn off, the headlights would dim down to a normal brightness and the cabin fan would go back to normal. Embarassing because at night cars in front of me thought I was putting my brights on them. I then tightened the alternator belt, which was easy. It didn't seem too loose, but obviously because it squealed, it was loose enough. Anyhow, now that it has been tightened, the squealing has stopped. However, the battery indicator light continues to come on intermittently. I just had the battery checked, and it's good. The mechanic then turned the truck on and ran the cabin fan full speed with the headlights on. The alternator was charging well. Of course, with my luck, the dash battery indicator light didn't come on for the mechanic. I'm thinking that it's maybe a relay? I re-seated the relays and fuses in the fuse box (next to the battery in the engine compartment), but that didn't fix it. I also re-seated the wires connected to the alternator. Any ideas?

 

Did you see alternator voltage output when mech "said" it is charging well?
Did you monitor alternator output voltage while having a problem? While not having a problem?
Do you see problem only when driving, and not when stationary? If so, there might be something intermittent caused by vibration.

What engine do you have? Manual transmission?
Check schematic...
1) Does your alternator IG terminal take its power from engine fuse like the 22R-E and
2) Does engine fuse also supply back-up light circuit?

If yes to 1 & 2, check wiring to back-up switch on transmission for chaffing/shorting to ground (like here) Mild, intermittent short may be enough to cause problem but not enough to blow engine fuse.

 

Most likely the contacts inside the distributor.

I had the same problem, and new contacts solved it.

 

mlkovacs,
When problem was occurring did you notice any change in engine running? RPM?

Not a difficult check so it would not hurt to check.

 

I didn't observe the voltage. I don't think that it's a vibration issue, because the problem occurs both when the vehicle is moving and stationary. As for distributor contacts, would I even have a distributor with a '98 Tacoma?

I'm going to check out the other questions tonight. I have a '98 Tacoma 5sp, ext cab, V6. I'm also thinking of temporarily transferring the fuse/relay box from our '99 4Runner to see if that finds the issue.

 

...but something comes to mind...even when the vehicle is stationary, if the engine is running, there still is vibration. I'll also check and see if I get the light without the engine running...

 

There is no distributor on a tacoma.

The belt could be worn out, causing it to slip still, could be a bad ground, poor connection at the battery or the alternator is on its way out.

 

You need to. IF light comes on when alt output voltage ("B" terminal/screw on post) is way outside the range of 13.5V to 14.5 V, it is doing its job.

Another possible cause for surging is if the sense circuit (the white 20AWG or so wire or the connector) wire is intermittently disconnected from battery positive.. When momentarily disconnected from battery, regulator would think battery voltage is low, and try to compensate by raising output voltage, When it momentarily re-connects, regulator sees the high voltage, and compensates by lowering output voltage. Either way would trigger charge fault light.

Oh no, don't start adding variables to the problem. Do the checks first and make sure you have good connections. That can be done by plain visual inspection and resistance measurements.

 

could be the belt is too tight also? sometimes you just need to replace it not just tighten it