I have recently got my 1992 PIckup back up and running. On occasion I get the red alternator and oil idiot lights illuminating then turn off. They only stay on a few seconds at time then go off. Today it happened several times. Also the other day the truck would start, then suddenly shut off. There was no warning when this happened. I ended up having to drive another vehicle. I got home and the truck cranked right up, this was last week. I started by checking the battery, all connections clean, I have replaced the negative cable earlier and properly grounded to passenger panel, it is not loose. I am not sure what this is and I was curious if anyone had any ideas. Thanks.

 

The alternator light will come on when the alternator is not producing power. One way for this to happen (which is not the fault of the alternator) is when the engine rpms drop far enough. Not coincidentally, low rpm will also slow the oil pump and drop the oil pressure.

If your lights aren't coupled to low engine rpm, you could have a bad alternator. Can you get it to light while not moving? If so, put a voltmeter right on the battery; if less than 13v or so at idle, the alternator is not charging.

 

Update it was the battery and brake light I find this to be a strange combination. Any ideas on why these come on together. I also notice the Rpms change could this be a belt slipping momentarily?

 

Other posts with this light combination indicate the voltage regulator (internal to the alternator) has gone wonky and was fixed by replacing the alternator. Test your alternator
Try this google search, battery and brake light on: yotatech

 

When both lights are coming on, it means your having charging issues and the alternator is probably on its last leg. Get it checked out and if its the stock toyota one have it repaired and if its an aftermarket one just replace it.

 

Yes. Issue with charging system. Need to verify exactly what is broken.
See my sig for charging circuit explained and do voltage checks to find out exactly where problem is.

 

FYI main ground should be to the engine block with a secondary lead to inner fender. pull alt and check brushes. Is the alt coated in oil?

 

Wait, has this always said OIL light and battery light in the thread title?
What I said earlier applies for the alt and brake lights. If the oil and alt light are coming on its something different.
Usually the only time those lights come on at the same time is when the engine is idling really low and not producing enough electricity and not enough oil pressure and is about to stall.

 

You mean exactly the Engine oil idiot light and not the Auto Transmission Oil idiot light, correct?

Correct, like scope said ^^

 

Thanks guys I will dig in. I cannot change the title, I saw the two lights next to each other and I thought it was oil light. I had the alternator checked by O'reillys they said it was fine. Don't trust the diagnosis this problem is intermittent.
I started seeing it more frequently the last few days and learned it was brake light. The problem appears to be getting worse, I will get on it immediately. Thanks for all the help guys. This forum rocks!

 

skoob, what do you want the title to read?

EDIT: Title changed per skoob.