Alt light on with brake light

[fbmustang1969]

I have an 85 w/manual trans. The problem is the Alternator gauge light comes on (reads about 12 volts with light on, about 14 off) and when the light comes on, so does the brake symbol. The lights would go off if the engine was spinning about 4000 rpms. Brake fluid level is good. Is my alternator going out?

[Donn29]

Yes, the Alt light triggers the Brake light for some reason.

[Mercuralis]

When your alternator goes out, you'll get the Alt light plus the Brake light, only you'll get no voltage reading either. It sounds like there are issues going on with your Alt. It might be going out, or it might just be bad wiring.

[Donn29]

...only you'll get no voltage reading either...

That incorrect, there will always be voltage, especially if the lights are on.

Pull the alternator and take it to a mom and pop shop, tell them to replace only what it needs.

[83restomod]

could be the charge lamp relay, bad alt, e brake plug came unclipped or broke. check the simple things first before you take the alt off. also with the car running take off the cable from the batt and see if the car stays running. if it dies alt is bad. if it runs check all other things that were mentioned

[supkar]

I like Restomod's backyard, shade-tree mechanic's tricks which, by-the-way, work very well. Yeah, pull the batt. cable and see if it still runs or go to a discount parts store and they'll come out and test it (alt. and batt) for free in the car. Brake light and alt. light on USUALLY means the alt. going out. I have a couple for sale and so do others on this forum, I'm sure. You can PM me if you want.

[frobozz]

For what it's worth, if you look at the schematic, you'll see that Toyota purposely wired it so that if the Alt light comes on, the brake light also comes on (but not the other way around.) I'd love to know the reasoning behind that, any Toyota engineers lurking out there?! (as if...)

My best guess is that the alt light is simply too subtle and you wouldn't see it when it was on... but light up that big red BRAKE warning light, and people are going to notice, and do something about it! So this was a quick-n-sleazy fix, rather than redesigning the dash to have a more useful alt light.

Duncan

[Donn29]

could be the charge lamp relay, bad alt, e brake plug came unclipped or broke. check the simple things first before you take the alt off. also with the car running take off the cable from the batt and see if the car stays running. if it dies alt is bad. if it runs check all other things that were mentioned

I wouldn't suggest doing that, my voltage regulator died when my Brake and Batt light started flickering, I was hitting 16V, eek! It's quite likely that had I disconnected the battery the ecu or something else may have been destroyed at +18V!

All in all, fb, read my Post that I have linked in my sig, It'll do you good.

[Lexusboy]

I have an 85 w/manual trans. The problem is the Alternator gauge light comes on (reads about 12 volts with light on, about 14 off) and when the light comes on, so does the brake symbol. The lights would go off if the engine was spinning about 4000 rpms. Brake fluid level is good. Is my alternator going out?


donn29: thats exactly what is happening to me... hmm well thats good to no i guess. maybe the alternator is just dirty we shallsee

fbmustang1969: does it die out from idling every once in a while? like at a stop light, or wont start up again after a dead stop every once in a while like your battery is dead? and then you have to push start it...in traffic...by yourself... up a hill... >.<

[Donn29]

fbmustang1969: does it die out from idling every once in a while? like at a stop light, or wont start up again after a dead stop every once in a while like your battery is dead? and then you have to push start it...in traffic...by yourself... up a hill... >.<

That sounds like the little copper contacts in the solenoid in the starter, a super cheap fix.

[Mone]

I'm glad this is a recent thread. I won't feel like I'm reviving it too badly.

I had this problem with my first 82. I bought an alternator with a lifetime warranty and swapped it. I was getting the red light and the e-brake light, and it would drain my battery. It ended up killing 3 alternators in 4 months before I took a closer look on the car side to see that one of the three prongs was bent over (inside the little cover that goes on the main alt plug). After straightening it out, no more alt issues, no more red lights, no more dead batteries.

Now my friend's 83 is having the same issue, so I'll be troubleshooting it all over again. Hopefully I can repro it.

[Lexusboy]

mine turned out to be a loose connection because i didnt tighten it enough ::::

[david]

Every since I have owned my 1985 Toyota Celica Supra I have gone through three sets of alternators and batteries.

The cause, bad connectors. These are the connectors in the driver's and passenger's side front kick panels. Water seeped from the window pillars into the area where the connectors were causing corrosion and eventually causing electrical short circuits. I cleaned the connectors with oil based paint thinner and WD-40, no more electrical problems.

Also anyone know where I can get one of those rubber covers that goes on the top electrical connector (nut) on the alternator. The one that looks like a right angle spark plug cover (cap).

[AChan]

Strange...I am having the same problem. The thing is, I installed a brand new alternator a month ago. But this was also around the time I installed a new power steering high pressure line. It is possible I spilled some PS fluid on the alt...So maybe it went bad because of that. The strange thing is that these lights turn off after driving it for a while or if I hit a bump...

But aside from this, I have had some electrical problems ever since I got the car. The light bulbs in my tail lights stay on as if I turned the lights on. What could this be?

[alfun]

my alt and brake light comes on too while i am driving sometimes. sometimes the voltage meter spikes and sometimes it doesn't, but after a few seconds both the lights turn off. i thought it was a loose battery terminal, bad alt belt, or powersteering fluid dripping on the alt but everything looks ok.

[Donn29]

It is possible I spilled some PS fluid on the alt...So maybe it went bad because of that. The strange thing is that these lights turn off after driving it for a while or if I hit a bump...

But aside from this, I have had some electrical problems ever since I got the car.

Sounds like it! Try to recreate the symptoms with the engine idling.

[AChan]

Sounds like it! Try to recreate the symptoms with the engine idling.

I got the alternator tested, and it was perfect. I just cleaned the connections and it solved the problem. The connection was gunky and the positive battery to alt was wet with PS fluid...

I'm glad that is taken care of, but my tail lights stay on when the battery is connected...:duh:

[Donn29]

I got the alternator tested, and it was perfect. I just cleaned the connections and it solved the problem. The connection was gunky and the positive battery to alt was wet with PS fluid...

I'm glad that is taken care of, but my tail lights stay on when the battery is connected...:duh:

Like the brakes are on or like the corner lights(does pushing the brake pedal make the lights get brighter)? Sounds like the brake pedal switch is buggered.

[AChan]

Pushing the brake pedal makes the tail lights brighter. The parking lights just stay on when the battery is connected.

[Dave A.]

Maybe these two pages in the TSRM will help: http://www.cygnusx1.net/Supra/Library/TSRM/MK2/manual.aspx?S=E&P=15

http://www.cygnusx1.net/Supra/Library/TSRM/MK2/manual.aspx?S=E&P=16



Is anything else staying on besides the parking lights?

[Donn29]

Pushing the brake pedal makes the tail lights brighter. The parking lights just stay on when the battery is connected.

So all of the corner lights stay on? Or does turning the parking lights on, turn the rest of them on? Sounds like the wiring to the combo switch is bad(as is shorted), or the relay failed in the closed position. You can probably pull the corner light relay to turn them off.

[AChan]

Thanks for the help, but I am terrible with wiring diagrams.

If it makes a difference, when I got the car, there was an aftermarket alarm partially installed...And there is nothing on my headliner. No sunroof controls or dome light. But a dangling wire from the dome light is there.

[Donn29]

Thanks for the help, but I am terrible with wiring diagrams.

If it makes a difference, when I got the car, there was an aftermarket alarm partially installed...And there is nothing on my headliner. No sunroof controls or dome light. But a dangling wire from the dome light is there.

Well theres your problem!