Help diagnose this electrical problem

[KKruger]

Brake light comes on at random times. Checked the fluid and float, both are fine, float is on top. There is no rhyme or reason as to when the light comes on, not like I hit a bump or steer or anything, I have disconnected the Ebrake connector to eliminate that as the issue. Completely random. When it does come on, the alt needle will start sweeping from 25 to 75%, based on engine RPM. Then the light will randomly turn off, after a minute, or 10 minutes or more, and the charge needle is back steady at 50%. ETAC? Bad ground? I am at a loss. Any ideas?

[kev]

_{Clean your contacts in your ignition switch. See Ken's instruction here:}

 

_{http://www.starquestclub.com/forum/index.php?showtopic=92298&st=20}

 

_Kevin

[KKruger]

Ok I read through that and the related threads but I honestly don't think that is the issue, because when it is working right, it works perfect. Alt charges fine, the blinker does not effect the charge needle, everything is bright and powerful. It is only during this intermittent problem, the brake light randomly coming on, that everything goes awry, the alt is having a very hard time powering the battery, the lights dim, at stop lights the signal lights and stereo stop working. Then after a bit, the brake light goes off, and the voltmeter jumps up to 75% to get the battery back up to speed. Normally, when I first start it, the brake light is off. Then after it gets warm, it will pop on, then intermittent. Although sometimes it has been cold when I started it and the brake light was on. It seems like it may be heat related, but that is not for sure. So far, I have replaces the main 4 fusible links (4 because it is an 86, I understand other years have the big 5 that go out), and I have run the car with the ETACS unplugged. I have inspected the grounds and don't see any issues. This same thing happened years ago when I would pull the E brake, and I tried to diagnose it then, with no luck, so I just unplugged the E brake sensor. It worked fine for years, but now the problem is back even without the E brake plugged in. I looked at the wiring diagram, and the E brake sensor runs directly int to ETACS, so I immediately eliminated that as the culprit. I have not tested the alt yet, but it works great when it is all good. Could it be an intermittent issue with the alt, and would testing it even find the problem, considering it is random? I am at a loss. I appreciate the ignition advice, but after reading the post and the related posts, it doesn't seem like it is the same issue. because of the intermittant aspect to it. It seems like something may be grounding out somewhere, but is there a way to isolate it? Could a well equipped shop find a fault like this without tearing everything apart?

[Metric-man]

The battery needs to be fully charged, and the alternator tested.

 

You could have one bad cell or the alternator's regulator could be on the way out.

 

 

87's had a TSB on the ETACS that ran down the battery,

there is a part number to look for on the defective ones

Your profile reads your car is an 1986,

I would still check the part number.

(MB510682)

 

 

http://www.starquestclub.com/forum/index.php?showtopic=61301

 

Even if your battery has recovered according to your dash gauge,

You need to place it on a charger so the alternator if not already weak to the point of replacment doesn't become over worked.

The alternator is for maintaining the battery's level but only to nominal levels, if your battery continually needs to be maintained/charged by the alt and it's designed limits, the alternator's life will be compromised.

[KKruger]

Deleted double post Edited November 3, 2012 by KKruger

[KKruger]

Solved. First of all, I have been told on the forums that the only time the dash brake light comes on is when the fluid is low, or the float is stuck, or the e brake is engaged. Not true. At least on an 86. On an 86, the dash brake light also doubles as a charge warning light. It is wired this way from the factory. So, when the alternator is going out, or not charging enough, the brake light comes on with a brightness relative to the discharge. I had the problem and the symptom reversed. I saw the brake light coming on as an indicator of a bad ground or short and went on the assumption that it was causing the discharge. I was wrong. The regulator was going out, and the odd, random timing of the light coming on was the alt overheating, the regulator shutting down, then it would cool off and charge fine again. Replace the alt, problem solved. There is another issue with this as well. About the time I did the GM alt conversion many years ago, my e brake, when engaged, would cause a massive current draw, and not allow the car to charge. I assumed there was a wiring problem with the e brake indicator circuit and just unplugged the wire at the handle. Problem solved temporarily, until I could diagnose the problem. Well, I couldn't, so I just left the e brake connector unplugged, and ran that way for years. So, now, instead of the brake indicator light illuminating relative to the discharge condition, it would just come on full blast during discharge, confusing me into thinking that there was a wiring/ground issue when the alt finally started giving out. The GM alternator needs an indicator light in its' circuit to operate correctly, and I do not think that the GM and Mitsu operate exactly the same way. So, by disabling the e brake, I was screwing with the alternator function. possibly relating to its' early demise.I also think there is a possibility that the GM alt conversion is the reason my e brake wiring was pulling on the electrical system in the first place. Has anyone else done the GM conversion on an 86? I would like to know if they had the same issue with the e brake. Well, there it is. Many, many hours of troubleshooting by me and others. Bottom line, the brake indicator light is also the charge warning light on an 86.

[Tim_C.]

Yes, the GM alternator needs a lamp circuit. As long as there is a circuit there, it should work fine. E-Brake on/off shouldn't affect it because it simply thought the e-brake was always off.

 

glad you got it figured out and fixed!

[KKruger]

Thanks Tim. I bought the kit from your gp many years ago. I installed a stock GM now (a cheap one) and kept the GP core. What do you suggest as far as a rebuild. I want to rebuild the one I got from you and reinstall it. I see there is a "Western alternator" sticker on it. Should I have them do it? or a local guy? I'm in San Diego. Thanks

[TexasQuest]

Solved. First of all, I have been told on the forums that the only time the dash brake light comes on is when the fluid is low, or the float is stuck, or the e brake is engaged. Not true. At least on an 86. On an 86, the dash brake light also doubles as a charge warning light. It is wired this way from the factory. So, when the alternator is going out, or not charging enough, the brake light comes on with a brightness relative to the discharge. I had the problem and the symptom reversed. I saw the brake light coming on as an indicator of a bad ground or short and went on the assumption that it was causing the discharge. I was wrong. The regulator was going out, and the odd, random timing of the light coming on was the alt overheating, the regulator shutting down, then it would cool off and charge fine again. Replace the alt, problem solved. There is another issue with this as well. About the time I did the GM alt conversion many years ago, my e brake, when engaged, would cause a massive current draw, and not allow the car to charge. I assumed there was a wiring problem with the e brake indicator circuit and just unplugged the wire at the handle. Problem solved temporarily, until I could diagnose the problem. Well, I couldn't, so I just left the e brake connector unplugged, and ran that way for years. So, now, instead of the brake indicator light illuminating relative to the discharge condition, it would just come on full blast during discharge, confusing me into thinking that there was a wiring/ground issue when the alt finally started giving out. The GM alternator needs an indicator light in its' circuit to operate correctly, and I do not think that the GM and Mitsu operate exactly the same way. So, by disabling the e brake, I was screwing with the alternator function. possibly relating to its' early demise.I also think there is a possibility that the GM alt conversion is the reason my e brake wiring was pulling on the electrical system in the first place. Has anyone else done the GM conversion on an 86? I would like to know if they had the same issue with the e brake. Well, there it is. Many, many hours of troubleshooting by me and others. Bottom line, the brake indicator light is also the charge warning light on an 86.

That is some good info to know there. Cause when I've had alternators bite the dust before, the brake light was also on very dim the same time the battery light was on.

[Metric-man]

Why would there be a battery voltage gauge if this were true?

Both the liquid chrystal and anolog dash have battery voltage gauges.

 

The ETACS will flash the battery indicator, if the parking brake is engaged while the vehicle is moving.

There should also be an audible alarm at around 2mph but once 2mph is passed the audible alarm shuts off.

 

Maybe? should? probably? could of would of? checked the ETACS?

[KKruger]

1. Why? To draw they eye. Not everyone notices the gauges, but an idiot light gets attention. Lots of cars have both.

 

2. Wrong. My car has an ammeter, not a voltage gauge. 86s are wired much differently than 87s. Some years had a volt gauge, some had an ammeter. Take a look at the FSM and wiring diagram. Those differences include the ebrake alarm as well.

 

3. If you took the time to reply, you should have taken the time to read the whole thread. The ETACS was eliminated as the issue earlier in the diagnosis.

[Metric-man]

Your description of the battery meter makes the whole idea of the brake light ,

having the secondary purpose of current drain sensor even less believable.

 

Idiot lights are typically check engine lights not brake lights, your correct that 86's are wired differently

the major difference in the gauge cluster is the dimmer switch and the ammount of current it draws.

I would believe the dimmer switch overloading and illuminating the brake light on the gauge cluster, before the assumption of a secondary use of the brake light senario, there is still the possibility of the vehicle speed sensor and it's interaction with the ETACS and the gauge cluster for the brake warning light.

My information comes from experience and the 86 FSM.

 

So yes your explanation of the problem with the GM alt conversion makes sense,

but the reasoning by the use of the brake warning light does not.

[KKruger]

These posters may beg to differ.

SFBMX88

 

http://www.starquestclub.com/forum/index.php?showtopic=127777

The swap took almost a whole day. To clarify everything, I had to combine the charging diagrams from both an 88 and 86. Just a note, the red brake warning light on the dash of the 86 is also tied into the charging circuit. So, if you are having alternator issues, your dash brake light will illuminate. I think 87 and up has a separate charge/battery light.

mikec

 

http://www.starquestclub.com/forum/index.php?showtopic=77688

Dash brake warning light comes on for:

* brake fluid in the reservoir is low... or the float is stuck down as Jimmy noted.

* parking brake switch (in center console) says the parking brake handle isn't all the way down.

* the alternator output voltage is nil. The "bulb check" for the brake light ties into the alternator/charge light via a diode... so when the alternator isn't working you get BOTH the charge light (battery symbol light) and the brake warning light.

[ghinckley68]

The alternator belt broke on my 89 and the brake light came on as well. So the 89s or wired that way also.

[Metric-man]

These posters may beg to differ.

SFBMX88

 

http://www.starquest...howtopic=127777

The swap took almost a whole day. To clarify everything, I had to combine the charging diagrams from both an 88 and 86. Just a note, the red brake warning light on the dash of the 86 is also tied into the charging circuit. So, if you are having alternator issues, your dash brake light will illuminate. I think 87 and up has a separate charge/battery light.

mikec

 

http://www.starquest...showtopic=77688

Dash brake warning light comes on for:

* brake fluid in the reservoir is low... or the float is stuck down as Jimmy noted.

* parking brake switch (in center console) says the parking brake handle isn't all the way down.

* the alternator output voltage is nil. The "bulb check" for the brake light ties into the alternator/charge light via a diode... so when the alternator isn't working you get BOTH the charge light (battery symbol light) and the brake warning light.

 

I understand what your point is but, you were stating the brake warning light has another fuction,

besides the brake system and "doubles" is not a correct description,

you also did not mention if the alternator /charge light was illuminated at the same time,

in your example..

 

The wiring diagram in the 86 FSM also shows the same circuit shared by,

the wash ( windshield water resivior)

and the oil warning light. (in the analog dash circuit diagram).

 

Please excuse me if I offended you by trying to clairify how you came to your solution,

but I don't see any need to go further.

 

For example, If you have a flat tire and want to say it became flat because,

a nail pushed the air out , I can't agree with your conclusion but we both can agree with the cause.

Edited November 5, 2012 by Metric-man

[KKruger]

The 86 doesn't have a battery light. That's why I didn't mention that it came on. I only quoted that post to supply additional information concerning the brake light coming on during low charge conditions and a way to point out the differences in the wiring of the different years. That car was obviously not an 86 because it had a battery light. But to suggest that It is wrong to think it is possible for a car to have a gauge and a corresponding idiot light (see fuel gauge and low fuel light, temp gauge and high temp light, both of which the 86 has, and a volt meter with a corresponding charge light, which the 88, for one example, has) is not a sound analysis. In addition, your assessment that idiot (or tell-tale, the more international term), are typically check engine lights, is not something I would agree with. Whether or not the factory built it to have the brake light come on during low charge conditions is something that none of us will probably be certain of, but to me, IMHO, it appears that in at least the case of the 86, it was designed that way. Either way, the fact remains that it does double as a low charge indicator by its' operation. I am not offended by your comments, in fact, I appreciate all the information anyone provides. I am just trying to add any information that I can for anyone that has a similar problem. Although I don't think your nail in the tire example holds air.

[Metric-man]

Did you eliminate or disable the rear anti-skid hardware from your car?

[KKruger]

No, never been messed with.

[Metric-man]

No, never been messed with.

 

Have you read the brake section of the 86 FSM,and

also regarding precautions regarding EMF interference?

[Metric-man]

The brake warning light is wired in a parallel with the alternator charging voltage circuit,

This will cause the brake warning light to illuminate not solely for a secondary indicator for a malfuction

of the charging circuit, but as an ABS (rear brake lock-up control) circuit fault warning.

 

The ABS (rear anti-skid) circuit is susceptible to voltage inconsistencies by the sensor components design,

but uses a fail safe mode to allow normal rear brake hardware use without the added safety,

of the anti-skid feature.

Since this safety feature is presumed automatically, a failure to the circuits system is also communicated through the brake warning light illumination (red) as well as the anti-lock warning indicator light (amber)

Edited November 10, 2012 by Metric-man