Red Light on Dash on, Need Help!
 

The lower red light on my dash is on. It doesn't seem like the alternator is charging the battery either.

Do I just need a new alternator or is there something else that could be wrong. I just got the car running for the first time in a couple years so if anything could happen from sitting then that could be it.

Thanks in advance for the help.

It could be an assortment of things. First, make sure the fan belt is still on. Then, put a voltmeter on the battery and see what you get with 1) the motor off 2) with it running 3) with it running with everything on (lights, AC, etc).

If the car's been sitting for two years i'd charge the batt. and drive it a bit.
The alt. might come into it with a little use.
If the light dosen't go out after a while then it may be alt. time.

I wouldn't drive it too long, as that light on most cars usually means a voltage below 13 VDC, which means no charge. The car will probably only run an hour or two on the battery charge, depending upon the condition of the battery.

The alternator is not likely to start working again without intervention. I would first verify the voltage at the battery while running. If it is below 13, it's likely the alternator or voltage regulator which is a component of the alternator. If the fan is turning, the alternator is turning.

It is possible that other odd things could cause this, such as shorts, but alternator is top of the list. Most manuals will give instructions for testing the alternator.

If the measured voltage is around 14, indicating a charging state, you will need to dig harder on the cause of the light and beyond my expertise with these cars.

Good luck,

Larry

Thanks for all the help guys. I really appreciate it.

I had the alternator tested at the local auto parts store and they said it is charging. The battery tested bad, but I have since tried a few different batteries that I know are good and it still has the light on.

I've also checked all my wires and cleaned all my grounds. They appear to be good.

Could the voltage regulator be the problem? I have a little experience and usually a bad one causes over-charging, not under-charging, but that is not on a Porsche so I don't know.

Have you checked the tightness of the fan belt? Is your idle speed correct? Does the light go out when you up the rpms?

Other items to consider: Are the battery connections clean and tight? Take them off and give them a good cleaning, same with the wires to the alternator. Check the wiring with an ohmmeter for shorts or bad spots. Check the voltage at the battery with ignition off and again with engine running even though the parts store checked it you should check in the car. If it is low with engine running then you have a bad alternator or a serious drain.

To really determine the problem we need to know the voltage at the battery in all conditions. Also, consider that a bad battery will suck up all the output and drag the voltage low as it eats amps. If you have a good battery in another car that is fine try hooking that in and taking the same readings if light stays on, similar readings point to the alternator.

The fan belt is tight. I've removed the alternator and cleaned or replaced every connection. The light stays on at all rpms.

One weird thing I noticed is the light gets brighter the better the battery. The battery in the car was a little low so I attached another one to help get the car started. The light got brighter when I hooked the other battery.

I am going to put the car back on the lift tonight and follow the wiring back through the car and check it out.

Does it make sense that it could be a voltage regulator? Could that cause I under-charging situation? If I need an alternator then so be it, I just don't want to spend the money if I'm not sure. Thanks again for the help.

Also, I know my car originally had an external voltage regulator. Where would it be if my car still had one? I am trying to figure out if my alternator has been replaced with an internal regulating model. It does have the replaceable brushes if that helps. Thanks again. Y'all are great.

Could just be a blown diode too. Certainly a regulator can fail and cause an undercharge if the failure mode is correct, but that is unlikely in the regulators used in the early cars. If I had to bet, based on your description, you have one blown diode, and that causes a slight "bucking" of the full voltage.

Isn't a diode an internal part of the alternator? So that would me I need a new alternator or is that something I can replace separately?

Separate part for the rectifier assembly. Plus, if you have a meter that can test diodes you can even find the faulty one and then rather than spend 60 bucks on the whole assembly you jsut get a 1.50 part.

How would I got about changing a diode?

Also, What is the difference between the top light (battery light I think) and the bottom light. The bottom light is the one that is on in my car and to clarify, it should go off when the car is running?

So, I finally got my multi-meter to work. It's reading 12.4 v with car turned off at the battery and 12.15 with the car running at idle and 2000 rpm.

With that voltage your alternator is not charging. The shop you took it to is nuts. You need to search the posts. If the alternator has been upgraded to one with an integral voltage regulator you may have to add a resistor to the light. The factory manuals showed how to do this and it is in the board's archives. Also make sure the alt light is the correct one. The light is an integral part of the charging circuit. Essentially if the battery voltage is higher than the alternator side the light comes on. I forget all the details. Do a search. You will find a wealth of information.

Yep... Time for an alternator.

Ok guys, looks like I need to break down and get an alternator. Or see if I can have mine rebuilt. I think it's a bosch model with a external bosch regulator. I'll start the search.

Is there anyway to make absolutely sure it isn't the external regulator before I spend money on an alternator?

Thanks for all the help.

Yes - remove your alternator and take it to a reputable repair shop. They will test it before rebuilding. I've had mine rebuilt twice, as I have been resisting the switch to an internal voltage regulator. I like my external one - no reason, I just do. I think, if you purchase a new or rebuilt alternator, it will be superseded by one with an internal regulator, and you will have to convert your car over. Lots of info on here regarding that. Do what you think is best for your circumstance.

Ok, ordered a new alternator. Another Bosch unit with the external regulator. I think is the problem and otherwise it won't hurt anything.

on tach
the upper green light is your low oil pressure warning light.
the lower red light is you alternator warning light.

my green oil idiot light isnt wired so it never comes on
but my red alternator light stays on at start up till i rev past 2000. then it is fine(off) if the idol stays above 900 rpm.

Well, finally got my alternator on Friday afternoon and it doesn't fit. The studs aren't long enough to go through the fan housing and it didn't come with a nut for the shaft......so I'm making some phone calls tomorrow.....

me think you got the wrong Alt! probley has the internal regulator,you don't get a nut for the shaft, it goes in the fan and the outer pulley half is the nut.

Definately have the wrong year alternator. Something here that should be clarified... If you removed the alternator and took it to a shop and it tested fine, how do you know the voltage regulator (external on your car) is OK? After all, that was still on the car when the alternator was at the shop.

Voltage regulators can be "flaky" when they fail. When the regulator on my 81 failed (mine is internal, doesn't matter, does the same thing), my alternator decided it would be really super cool to throw out 19 plus volts. Blew the bulbs on my headlamps which is what got me looking for a problem to begin with. I must say though that the power windows went up and down REAL well - LOL! Red light stays off on an over-charge...

My husband's 85 (another internal) has been acting up. He drove down the an electric shop and had the car tested at the shop. Diagnosed as not-charging (11.5 or so volts), red light on. He brought the car home. It sat a week or so and he fired it up to turn it around so the rear was in the shade instead of the sun and planned to remove the alternator. Guess what? No red light! Threw a voltage meter on it and it was charging at 16.8 to 17 volts... Not good, pulled it and will take it down to the electric shop for a regulator replacement and rebuild as the bearing feels a bit gravely.

Also, let me share a tip a Pelican dude gave me. Find a ground and a hot inside of your car and put your voltage meter to it. Drive like that if you continue to have a problem to diagnose under/overcharge. I popped the clock out and used the hot/ground from the clock for this purpose. Looks goofy, works well.

angela

http://forums.pelicanparts.com/uploa...1253541217.jpg

[Bulb on the fuel guage is flashing]
Kowalski: Skipper, look.
Skipper: Analysis
Kowalski: It looks like a small incandescent bulb, designed to indicate something out of the ordinary, like a malfunction.
Skipper: I find it pretty and somewhat hypnotic.
Kowalski: That too sir.
Skipper: Right. Rico, Maunal!
[Catches the manual and smashes the bulb with it]
Skipper: Problemo solved.

http://forums.pelicanparts.com/uploa...1253543147.jpg

Wait for it, Wait for it, NOW.

http://forums.pelicanparts.com/support/smileys/lol2.gifhttp://forums.pelicanparts.com/support/smileys/lol2.gif

The shop that tested the Alternator could have told you if it has an internal or external regulator.
Why not ask them??????????before odering a new alternator????

An external regulator would be located on the left side inner fender of the engine compartment.
Take a picture of the area where the filter is and we'll tell you if you have it.

Why not have your alternator rebuild to have an internal regulator?

It's a lot cheaper than a new one. :)

I know for sure it has an external regulator. My local parts store is suppose to have one here for me tomorrow morning. If that doesn't do it then I'm taking the alternator to get rebuilt.

Having exactly the same problem-not trying to hijack your thread, but ask a simple question.

Does anyone know how to test the regulator?

Alterator and internal regulator are tested together on the bench.

If you have an external regulator, it's easy for a shop to test it in situ.
They'll put some leads on and tell you if the alternator is charging and if the regulator works.

Ok, so I replaced the external regulator. Need a little wiring clarification.

New Regulator has: teal, dark brown (maybe black) and red wires

Car has: blue, brown and black wires

I think I know how it goes, but it doesn't seem to be working. Do any of y'all know how the wires match up?

OK. Finally got the alternator rebuilt.

So now I have a rebuilt alternator (which I assume works) and a new voltage regulator.

Light is still on. Still reading approx. the same voltage at the battery.

Anyone have any other ideas?

And, does anyone know anything about the regulator wiring question above? I want to make sure I am doing it right.

Ok, another interesting development. When I first start my car. The fuel gauge reads half a tank and if i honk the horn it drops to almost empty.

Does anyone know what that means?

How do you know that the new regulator matches your alternator?
Take the new regulator and the rebuild alternator to the shop that rebuild it and ask them how the wires go.

Better yet, charge your battery fully, then make an appointment, drive there and let them install and test in situ. Takes no time at all and elimminates any guessing. :)

Another dead end thread where some ****dhhaffhda asks for advice and help then never updates when he finds the solution... sooooo many thread here like this!!

Well, the OP sold his car in 2010. Maybe he gave up and sold it!

there are so many issues you go through threads and the OP just doesn't give a crap to update, it drives me crazy, ultimate show of selfishness lol ask for advice then disappear

I agree, many times you spend hours doing a search for a problem, reading the posts, and at then end, nothing. I will admit that this forum is nowhere near
as bad at this than most others.