My first post here. Though I've been a peruser over the years getting help for my truck.

At any rate I am at a loss.

I have an 87' 22re. The brake light and battery light have come on and off intermittently for a while now. At times my oil gauge drops and then will come back.

The other day I was stopped at some road construction and my stereo just died and my dash lights began to dim. I had about 5 miles left to go and then as I was climbing a small hill toward my destination my truck started to die all my dash lights dimmed and the truck was acting as if it would turn off.

Then I turned the truck off and back on. Same issues with dimming with lights off but dimmed when they were on. With lights on the rpm gauge went dead...with them off it came back???

I had a 30 min drive ahead of me to get back home. I stayed at my destination for a bit and then got back into my truck......turned it over....and no issues. Battery and brake lights went off as they should. I drove home with trepidation but with no issues at all.

Once I got home I turned it off and back on......battery and brake lights stayed on.

Did some research specifically on this forum and everything pointed to the alternator. Doing a voltmeter test the batter was at 12.2v or so and when turned over 11.9v. So I pulled it and went down to Autozone and had it checked. No issues with the alternator! ???

Put the alternator back in.......and no battery or brake light issues. Then I was going to go into town and there it was again!!!

Any help would be greatly appreciated.

Thank you in advance.

 

Pickup or 4runner?
What's your system voltage while running? Should be 13.3v to 14.5v.
I suspect you have a ground circuit losing contact. The diagram indicates there is a ground on the instrument panel brace, probably behind the cluster. If that is missing, the current will backfeed to another ground. The brake light has a different ground, and would illuminate because of this.

 

Puckup 4wd. Voltage from a simple battery test while running indicates 11.9v. With engine off about 12.2

 

Did you check the 7.5a charge fuse?

 

It is possible the wire coming off the alternator B terminal going to the fuse block is no longer conducting like it should.

When the battery and brake light are on It is to get your attention that you have a electrical problem.

Another problem could be the other plug on the alternator is corroded removing and reinstalling may have made it work better for a short time.

Any of the battery terminals loose broke or corroded will cause this issue.

These trucks have rather small battery cables from new

Is your alternator belt working loose it was tight after you reinstalled the alternator now loose again.

Once the voltage drops below a certain point the ecu will power down leaving you sit.

Charge your battery with a charger.

Then it might be the battery is dieing

 

My temp gauge will act funny sometimes, slowly start rising as it warms up then goes to about half way up. Sometimes it goes back down and then comes up as you would expect. Also, sometimes my tach will read a little high, rev it and it comes down where it should be. I found a similar problem posted here with a fix. The screws are loose on the printed circuit board. Something to think about. Here's the post.

https://www.yotatech.com/forums/f116...inally-218848/

 

Just checked......the fuse seems fine.

 

Great suggestions guys.

My temperature gauge seems to be fine. It is my oil pressure that has done an intermittent thing from time to time.......and did it again today. Would the PCB trick be connected to the oil gauge as well. I am supposing so at this point.

I'll do some tests on the cables as well to see about current.

But with things as they are, there is some sort of short which could mean I might get a good reading even though it is bad. I wish there was a fail safe way of knowing and most of the mechanics in my neck of the woods are crooks.

 

Pls see my sig for charging system explained, and do suggested voltage checks.

You should measure output voltage at "B" terminal (screw-post) of Alternator. 11.9 - 12.2V is too low. Charge light is doing its job, telling you there is problem with alternator / charging system.

Charge fuse does not prevent nor cause charging. It merely connects "L" voltage to the charge error light. Removing the charge fuse will not prevent alternator from charging. However, it will turn off the charge error light.

The Engine Fuse is what provides excitation at terminal "IG" in order for alternator to work.


Yes.
You should measure output voltage at "B" terminal (screw-post) of Alternator. Compare with voltage at battery post. If there is large difference, Like Wyoming says, there is a problem with "B" wire between alt post and battery post. Inspect the disconnect that looks like a ferrite choke. That part is useless and adds more potential point of failure.

 

These guys are steering you in the correct direction for sure.

I suggest you stop driving the vehicle for the time being.





If you keep on driving the vehicle without proper voltage going to the battery there's a very strong chance you will be purchasing a battery after you purchase a cable or terminals.

This is important because your alternator was never intended to be a "Charger" and making it charge a battery is heavy work for it. It will reduce the lifespan of the alternator.

 

Okay finally got the charging issue fixed. New alternator and battery......and we're all set!

The battery was pretty old.

Thank you all for your help.

Any suggestions for the intermittent oil gauge issue?