Help with dash lights? Brake, Rear lights and battery light

[Halsupramk3]

I have recently developed a problem with 3 dash lights randomly coming on and then shutting off, and sometimes just flickering. The 3 lights are the Brake light, the Tail Light light, and the battery light. When the lights come on nothing seems to dim down all my exterior lights stay on, and nothing seems to be wrong. The lights all always come on at the same time and shut off at the same time. Any possible answers would help. THANK YOU

Read the stated problem. No dimming a d all three lights come on at same time. In the dash wiring diagram all three of these lights are terminated to same point. Whe. The diode in an alt is bad 12v flows both ways. The voltage goes to the three wires for these lights and the light up.

I had this same problem over 10 years ago when some of u were still riding tricycles. 2 mech shops could not figure why the dash lights were on. The alt tested ok on the car as it was putting out 12v. This is why he stated the dash does not dim. If the volt reg was bad or output was low dimming may occur. Back then I looked at the wiring diagram and saw the wiring of the three lights coming together and that wires go to the alt. IIRC. So I removed the alt. When the alt was tested the diode failed. I would assume it is located in the regulator.

You may have a bad ground , loose belt, or other problem but I had this exact problem and it was fixed when I removed the alt and had it tested. When a new alt was instaled no more lights

If you have had the alt tested and pasted many times I would examine the wiring connected to the wire that is common to the three lights. If a frayed or loose wire is applying current to that wire the lights light up. It. maybe the cluster has a problem.

Current is being routed to these lights from some problem. This is not a warning light going off.

 

[jetjock]

While I don't doubt for a moment replacement of your alternator resolved the problem much of the rest is nonsense.

 

[suprasick]

Is this a horse and water story

I like the rendition, "You can lead a horse to water, but sometimes you have to shoot the horse."

 

[f00g00]

What happened with the OP? was the problem resolved? This thread got jacked a few times.
If the diodes are going bad the alternater will start to read ac voltage and you will notice that your lights vary in intensity at low rpm's.
If the alt doesn't read AC then I would try the regulator assembly for worn brushes.

 

[hvyman]

read the stated problem. No dimming a d all three lights come on at same time. In the dash wiring diagram all three of these lights are terminated to same point. Whe. The diode in an alt is bad 12v flows both ways. The voltage goes to the three wires for these lights and the light up.

I had this same problem over 10 years ago when some of u were still riding tricycles. 2 mech shops could not figure why the dash lights were on. The alt tested ok on the car as it was putting out 12v. This is why he stated the dash does not dim. If the volt reg was bad or output was low dimming may occur. Back then i looked at the wiring diagram and saw the wiring of the three lights coming together and that wires go to the alt. Iirc. So i removed the alt. When the alt was tested the diode failed. I would assume it is located in the regulator.

You may have a bad ground , loose belt, or other problem but i had this exact problem and it was fixed when i removed the alt and had it tested. When a new alt was instaled no more lights

if you have had the alt tested and pasted many times i would examine the wiring connected to the wire that is common to the three lights. If a frayed or loose wire is applying current to that wire the lights light up. It. Maybe the cluster has a problem.

Current is being routed to these lights from some problem. This is not a warning light going off.

the lights come on because of low voltage. A bad alternator is not the only reason those lights can come on.

 

[ZoomZoomZoom]

Rebuilt alternators suck. So do rebuilt master brake cylinders. Buy OEM. The darn stuff costs more $$, but heck, look how long it lasts.

 

[super51fan]

^^^ OEM only for alot of things. Or just waste your time and energy.

 

[Halsupramk3]

While I don't doubt for a moment replacement of your alternator resolved the problem much of the rest is nonsense.

Maybe I should not post 5 minutes before my colonoscopy. That procedure is like a ct26 with a blown oil seal.

The charge light, brake light, and rear light out lights all are connected together in the combination meter by diodes. The exact wiring I don't know. I.am reading the EWD. If current is low why do all three come on? Wouldn't the charge light come on solely? How is current getting to all 3 lights to turn them on? Why would all 3 need to come on to warn of low voltage?
The alt wire and rear light failure box wire are the wires going to the diodes in the combo meter. These are the wires completing the circuit to turn the lights on. If low voltage is turning on the charge light but the diodes are bad in the combo meter would that power the additional two lights accidently?

If the thread starter is still reading this thread the only things I can think of is the alt or combo meter or rear light failure box is causing the problem.

 

[3p141592654]

Its a good question, so why the diodes in the combo meter tying the three bulbs together? You would expect the charge light to be connected directly to the L terminal on the alternator and would light up when the alt signals a failure.

I suspect that the current in the L circuit during normal operation is too high on this alt and the light would glow dimly all the time. By spreading the current over three bulbs there is less current per bulb and no glow. If so, its a hack. Just a guess, I haven't ever measured the L circuit current.

 

[hvyman]

But if you ground the L terminal to light up the low charge light you also ground the other 2 lights. Which is why all 3 come on if there is low voltage.

Low voltage doesn't mean bad alternator or bad diode ether.

Low charge doesn't mean alternator or bad diode.

Diode is just a one way directional check valve for electrical current.

 

[jetjock]

...I.am reading the EWD. If current is low why do all three come on? ...

If you don't understand why all three come on you aren't reading the EWD correctly. That said the Toyota Charging Systems training manual goes into detail how the monolithic IC regulator operates and the three conditions which trigger the L terminal. I've posted them before and would again except I currently don't have access to my library.

As mentioned there are other, less likely, causes for the lamps to illuminate but it's usually due to low charging output or a disconnected sense line. Since the charging system is one of the simplest circuits in the car it should be a cake walk to pinpoint wherever the problem really lies.

Lastly, the compact alternator used is a rugged and well thought out design that can be easily overhauled. Mine lasted the life of the car (25 years) with only a single rebuild (cleaning, slip rings, brushes, and both bearings).

My sympathy regarding the plumbing inspection...