1st gen brake and charge light flashing??

[Leo Ahearn]

I have an '86.

Yesterday, driving down the road, the "charge" and "brake" light started flashing off and on, timed with bumps in the road, driveline on and off the throttle/shifting, etc. Clearly an electrical issue, not simultaneous problems with both systems that are somehow synced with each other.

I used the Haynes manual to trace the circuits for the two lights. They share a common ground, and for some reason I don't understand, a diode connects between the two lights.... humm.

Has anyone heard of this before? Does anyone know where this diode is?

Thanks, Leo.

 

[fourwd1]

Nothing unusual, your alternator is going up, usually the brushes.
You can replace them yourself.

 

[Leo Ahearn]

At the risk of looking like I talk to myself a lot I'll post the latest.

OK, so I asked myself over and over WHY the diode existed between the two lights. Then I asked the guy in auto tech school down at the local Autozone what he thought. He said if the second light is coming on it is because the diode is bad or it cannot shunt all that is being thrown at it... HUMM....

8 screws and one speedo connector later I have the inst cluster in my lap. Out comes the multi-meter. I test the voltage to the brake lamp. At idle, zero. At RPM, 9 volts....

I test the voltage to the CHARGE light. At idle, zero volts. At RPM, 16.6 VOLTS!!!!!!! I think I'm on to something here!!!!

I go back to the Autozone and have them drag out the electrical system check machine. Sho nuff, I gots a bad voltage regulator. Upon closer inspection of the battery, I see the weep holes are wet and there is some spray on the fender well and radiator hose.

So in the end, while the Toy engineers were smart enough to link the two lights via the diode to alert you to an overcharge situation, they were not astute enough to tell you so in the owner's manual nor was Haynes astute enough to put it in their book.

Time for a new alternator. The receipt in the glove box shows it got a new one, under warranty from NAPA, in 2004. Time to see if NAPA will honor this one as well.

 

[fourwd1]

... So in the end, while the Toy engineers were smart enough to link the two lights via the diode to alert you to an overcharge situation, they were not astute enough to tell you so in the owner's manual nor was Haynes astute enough to put it in their book...

Exactly, I guess I should have pointed that out, since you were questioning the diode.

Both lights on together means big alternator trouble, and the most common problem is the brushes.

BTW, if the Brake light ever comes on intermittently, especially when using the brakes, it's probably low fluid level in the MC.

 

[Leo Ahearn]

Thanks.

About 50 miles of driving with no VR managed to fry the battery as well. It was dead this AM. Was new as of 2/1/07.

I am being coached by a long time Toy owner that the auto store reman alternators are absolute do-doo and I'm inclined to agree with him. Got a used OEM Denso located 3 miles from here for $35. Gonna go that route.

 

[Leo Ahearn]

She's all back together now. The capper was having to pull the instrument cluster again to put the idiot lights back in. NAPA gave me a new battery in exchange for the old one so my net cost for the fix was $38

Hard to believe that the original alternator out of an '85 Celica is deemed more reliable than a factory rebuilt aftermarket but that sure seems to be the case.

Is there anything else I have overlooked that might be leading to premature voltage regulator failure? Both the used parts guy and the Autozone guy told me that new alternator + dead battery = fried VR, that you must have a charged battery in it when you replace the alternator. Otherwise if you jump it with a dead battery and try to get the alternator to charge you exceed the duty cycle rating of the VR and burn it up.

 

[LostinDartmouth]

1989 volt and brake light on....burnt smell under the hood.

Hello from Dartmouth:

once again I must thank this forum for finding solutions. Two nights ago, I left my key in the "on" or ACC position and drained the battery. Jumped it and drove for a half an hour to charge it. Didn't work and had to jump again.
Have since smelled a strange 'burnt odour from under the hood. Both the ALT and Parking Lights came on. Volt meter showed no charge.

So, I'll check the brushes and Voltage Regulator.

Do you know if I need to remove the alternator to do this or can the alternator be accessed in place?

Thanks
P

 

[illzoni]

Nothing unusual, your alternator is going up, usually the brushes.
You can replace them yourself.

Could you explain please?

I'm getting intermittent high voltmeter readings along with the aforementioned lights glowing at the same time.

Thx,
Jon

 

[fourwd1]

Hello from Dartmouth:

once again I must thank this forum for finding solutions. Two nights ago, I left my key in the "on" or ACC position and drained the battery. Jumped it and drove for a half an hour to charge it. Didn't work and had to jump again.
Have since smelled a strange 'burnt odour from under the hood. Both the ALT and Parking Lights came on. Volt meter showed no charge.

So, I'll check the brushes and Voltage Regulator.

Do you know if I need to remove the alternator to do this or can the alternator be accessed in place?

Thanks
P

You have to pull the alt out to work on it.

 

[fourwd1]

Could you explain please?

I'm getting intermittent high voltmeter readings along with the aforementioned lights glowing at the same time.

Thx,
Jon

Depends on what the "high" voltage readings are, and if you're using a real DMM instead of the dash gauge.

When the alt is not charging properly and the light comes on, voltage may drop below 13.8V indicating the batt isn't charging. When operating correctly the charging voltage is 13.8+ (can be as high as 16V or so).

 

[LostinDartmouth]

Follow up on alternator

Hi...a quick followup...had to replace the voltage regulator. Was over charging for awhile and then burned out completely. Brushes were also worn down with only a year or so left in them, so I bought a Champion new alterntor for $180 dollars (brushes and a regulator would have cost $130 anyhow...)..

Thanks for the help.

Alt and parking brake light are now off.....Problem solved.
Paul