Questions and Answers

Toyota Camry Alternator Diodes Q. Mr. Ciulla, I have a 1986 Toyota Camry, 4 cylinder, automatic transmission, with 254,000 miles. It has fuel injection, non-ABS brakes. It's got AC and cruise. I don't know about the P/S or the steering, but all of this is a sideline to my question. Yesterday, I started my car and the Rear Lights, Brake, and Charge lights on the dashboard all came on.

When I stop moving - come to a complete or near complete stop, the lights go off. When I start moving, they come back on. In Neutral or Park, so the car isn't actually going anywhere, the lights come on when I press down on the accelerator (above 1,000 RPM or so), but once I release the gas and the tachometer drops below 1,000 RPM, the lights go off. Before I parked my car, everything was fine. When I started it up, this started happening. I stopped and started a few times, and it continues to occur.

While sitting still, the brake light works fine - it comes on when I pull up on the parking brake handle, and it goes off when I put the parking brake handle all the way down. The brake lights also function properly when the brake pedal is depressed.

I checked my alternator/battery circuit last night. At idle, I measured 16 V potential between the alternator and the negative terminal on the battery, at 2,000 RPM, it got as high as 17.5 V. My manual says this should be 14-15.5V, so I was thinking about replacing my voltage regulator. I just had the alternator replaced at the local AutoZone about 18 months ago, because the old one finally died. My battery died earlier this year, so that's also pretty new (say four months old).

I checked the wiring diagrams I have, and was looking for the charge light relay, which per the diagram should be by my left foot when I'm driving - I pulled off the cover and found four empty slots for relays next to the fuses and a couple other relays, but no relay where I expected the charge light relay to reside.

I saw your answer regarding the alternator diodes as a solution to a similar problem on another 1986 Camry (Brake and Charge lights, but not the Rear Lights warning light). Do you know if these diodes are replaceable, or do I need another new alternator? Could the voltage regulator be the culprit behind everything, and would replacing it fix all this?

Thanks,
Ken

A. Yeah, it's probably bad alternator diodes. The diode pack is replaceable, but they can be tricky to put in and even trickier to find. The only place you will find it is at a Toyota dealer and it will have to be special ordered. The diode pack costs $118.00.

Once you have the diode pack, you have to open up the alternator and install them. You have to un-solder the old diode pack (7) and solder in the new diode pack. I used to be able to do it in about two hours.

I say used to because with the time and labor involved, it was more cost effective to just put in a rebuilt. If you want to give it a shot, the diode pack part number is 27357-63020.