Pretty quiet in here... what are you working on? (16 Viewers)

[emorth]

Never happened except when I first had the issue...then not until today. I do believe it’s the regulator. Reading at fuse is 13.5 volt on 1 side and under 1 volt on the other. I think the regulator is sending the wrong information to the fuse block. Per FSM that should read 12v at fuse block (I think)

Reading at fuse is 13.5 volt on 1 side and under 1 volt on the other. With the fuse installed this would indicate a blown fuse. Which also doesn't make sense since the lights went out when you pulled the fuse.

I think the regulator is sending the wrong information to the fuse block. I don't. Sorry.

Try to find a schematic.

Look for something pushing against the wiring harness. If something comes in contact with the harness and it has worn away the insulation on the wires for both lights, when it comes in contact it could cause both of the lights to light. Doesn't explain why it is idle related???? Maybe related to the throttle position??????

 

[Stumpalama]

For a 22re but I'm confident it's the same.
EDIT: 1986 4Runner = 22RE

 

[Stumpalama]

Reading at fuse is 13.5 volt on 1 side and under 1 volt on the other. With the fuse installed this would indicate a blown fuse. Which also doesn't make sense since the lights went out when you pulled the fuse.

I think the regulator is sending the wrong information to the fuse block. I don't. Sorry.

Try to find a schematic.

Look for something pushing against the wiring harness. If something comes in contact with the harness and it has worn away the insulation on the wires for both lights, when it comes in contact it could cause both of the lights to light. Doesn't explain why it is idle related???? Maybe related to the throttle position??????

Ed is the authority when it comes to automotive electrical issues.

 

[Stumpalama]

For your reading pleasure: 86 4runner charge light ??? - https://www.pirate4x4.com/threads/86-4runner-charge-light.1162906/

 

[Stumpalama]

Another: How Charging System Works - 22RE - YotaTech Forums - https://www.yotatech.com/forums/f116/how-charging-system-works-22re-304868/

 

[emorth]

Ohm my. The pressure is on.

Good links Stump. But, the alternator is charging ok at 14.4V and the brake circuit is unrelated. The first post mentioned damage to the wiring harness. At this point that would be what I would look for.

 

[Stumpalama]

Ohm my. The pressure is on.

Good links Stump. But, the alternator is charging ok at 14.4V and the brake circuit is unrelated. The first post mentioned damage to the wiring harness. At this point that would be what I would look for.

I discounted the relationship between the brake light and alt light early on. I did not see the mention of harness damage.

 

[emorth]

Whatever it turns out to be, this will be one for the books.

 

[Stumpalama]

It’s possible. When I flick on the AC it really struggles at idle. Doesn’t stall out but it definitely struggles and shimmies. The 14.4 volt was at idle however, and the battery with ignition off was about 12.5. But the lights go out when I’m getting the rpm up.... could be.

Picture of the damaged harness?

 

[Explorer4Hire]

I’ve read through a bunch of threads.... most of the just “fixed” it with a Toyota alternator. The brake lights is wired to illuminate when there is an presumed charge fault I think.... no? I remember this happening on my 22R (85) as well. Alternator was bad and everything fine after, but this alternator seems fine.... why then does higher rpm turn the charge/brake light off. This is making me feel so dumb. Haha.

 

[Explorer4Hire]

Charge/Brake Light On, Alternator OK - YotaTech Forums

86-95 Trucks & 4Runners - Charge/Brake Light On, Alternator OK - Yesterday the brake and charge lights came on in my 1990 pickup. It is a standard pickup, 22RE, 4 speed manual transmission. At first, I figured the alternator was bad, but I checked it with a meter and it is charging at about...

www.yotatech.com

I read through this as well. Lots of info. Post 23 or so is where I believe he concluded a regulator. But I’m at a total loss. I’ll sleep on it... pull the fuse for inspection tomorrow and then try some more diagnostics. Maybe I will have the alternator tested.

 

[Stumpalama]

I’ve read through a bunch of threads.... most of the just “fixed” it with a Toyota alternator. The brake lights is wired to illuminate when there is an presumed charge fault I think.... no? I remember this happening on my 22R (85) as well. Alternator was bad and everything fine after, but this alternator seems fine.... why then does higher rpm turn the charge/brake light off. This is making me feel so dumb. Haha.

I recommend you read and carefully follow the procedure outlined in the yotatech article I linked.
It says exactly what you were recalling about the brake light, but he explains the exact circumstances that trigger both lights to come on simultaneously.
AND he provides a step by step diagnostic procedure.

 

[76FJ40]

OBTW, there should be an "idle up" for the AC to increase the RPMs when the AC is on. It's been a loooong time but I think it's behind the evaporator.

 

[Explorer4Hire]

How Charging System Works - 22RE - YotaTech Forums

86-95 Trucks & 4Runners - How Charging System Works - 22RE - UPDATED WITH GOOGLE PHOTOS (https://photos.google.com/) (I'm posting this here so it will be easier to refer to, rather than re-typing explanation into various threads that need the explanation.) Here's the 22RE-liable schematic:...

www.yotatech.com

I did this test on post 7 and one side of fuse terminal reads correctly but the other side is under 1 volt.

 

[Explorer4Hire]

I recommend you read and carefully follow the procedure outlined in the yotatech article I linked.
It says exactly what you were recalling about the brake light, but he explains the exact circumstances that trigger both lights to come on simultaneously.
AND he provides a step by step diagnostic procedure.

View attachment 2657711

Yes. I have been reading this one. Doing my best as this is not my strongest area of knowledge.

 

[emorth]

I missed this part (underlined in red)
It doesn't make sense. This isn't shown in the schematic I have,

 

[StaleAle]

I got a set of forks for the tractor if you can get the 4r and bumper to my house. Maybe strap/hang the bumper under the forks and line it up.

Thanks Patrick! That's an interesting idea. I've got one other mod to make while I have the front grill cover off the truck to do the bumper/winch. I might have to pull the front cover off at Ed's place, do the mod and cut the cover, then drive over to your place with the bumper/winch to get you to sling it close enough into position that I can align the bolt holes and bolt it on. I'll need to do some more planning and verify I can drive it around without the front cover.

You'll need an extra set of hands and a floor jack, or 2 extra sets of hands. Good thing is its a quick and easy job, just need some helpers. I'll help ya out if you don't want to wait for a tech day.

Thanks Ahmad! I have some work to do to prepare for this install so timing is still up in the air. I'll let you know if/when we need a hand once I get my ducks in a row. Thanks!

 

[emorth]

I think I found the link between the alternator's "L" terminal and the brake and charge lights. This is from the 3rd gen manual. Does the 1st gen have DRLs?

So the "L" terminal controls the charge light and the daytime running lights. The brake switch controls the brake light and the daytime running lights. DRLs are the common denominator? Some Toyota EE didn't take into consideration the possibility of "back feed' from the L term to the brake light. Maybe the DRLs were added later and that created the problem? A simple diode would have prevented it. And why use the L term when they could have done the same thing with the ignition switch?

This also doesn't make sense that the DRLs stay lit when the alternator fails (engine stalls). If the alternator fails you want to minimize the load on the battery (turn off the DRLs) so it lasts long enough to get you to some safe place.

Mystery.

 

[Stumpalama]

I think I found the link between the alternator's "L" terminal and the brake and charge lights. This is from the 3rd gen manual. Does the 1st gen have DRLs?

View attachment 2657760

So the "L" terminal controls the charge light and the daytime running lights. The brake switch controls the brake light and the daytime running lights. DRLs are the common denominator? Some Toyota EE didn't take into consideration the possibility of "back feed' from the L term to the brake light. Maybe the DRLs were added later and that created the problem? A simple diode would have prevented it. And why use the L term when they could have done the same thing with the ignition switch?

This also doesn't make sense that the DRLs stay lit when the alternator fails (engine stalls). If the alternator fails you want to minimize the load on the battery (turn off the DRLs) so it lasts long enough to get you to some safe place.

Mystery.

Highly doubt (confident) 1986 4Runners did not have DRLs. Maybe parking lights...

 

[emorth]

Hmmmm. So much for getting any sleep tonight.