New here, and in desperate need of help!

J-70 · 08-30-2001, 07:34 PM

Hi,

My name is Jason and new to this board. My brother recently bought a 1970 911 with fender flares and a 2.7 liter fuel injection engine swap.

The problem is, 2 days after he purchased it, the charging light came on and my brother can't find the problem. He has brought the alternator to a mechanic, and it's fine. The battery is fine as well. He also brought the voltage regulator to be fixed, but that still hasn't fixed the problem. I think he has already checked the wiring and said it was fine. But the car still has the charging light on, and he is clueless on what is wrong. Anyone know what is wrong?

thnx, Jason

Superman · 08-30-2001, 07:44 PM

No, but it'll be interesting to see how long it takes for someone to have the answer. Stay tuned.

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'83 SC

CamB · CamB's Garage

Is the handbrake on or has the handbrake idiot light switch broken? Or is that the oil pressure idiot light, I can never remember.

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Cameron Baudinet
1975 911S (in bits)
1969 911T

J-70 · 08-30-2001, 08:38 PM

The top light is the handbrake light. The light under it is the generator light or something. It means the car is not charging.
Jason

Clark Griswald · Clark Griswald's Garage

Couple of questions:

How many miles on the engine? And the alternator?

What year is the engine?

Does the battery charge properly?

Is the light on all the time and at all rpms?

pwd72s · 08-30-2001, 09:54 PM

A good battery specialty shop should be able to test the voltage output...don't know other years, but in '72, it sould be in the 14.5 volts range, up or down, depending on rpm...

Rot 911 · 08-31-2001, 05:57 AM

Having learned the hard way, I have found it is always easier to buy the proper test equipment as opposed to the always expensive method of pulling and replacing parts. A decent digital multimeter can be had at Sears for less that $50.00. You will be able to use it on a lot more than you car. In this instance it will tell you if you even have a charging problem! With the car off, test the voltage at the battery. It should be around 12.5 volts. Now start the car. At around 1500 rpm voltage at the battery should be around 13.5 to 14 volts. If so, then you obviously have an alternator that charges properly. If not, well you either have a bad alternator or voltage regulator. In addition a faulty diode in the alternator can cause the light to come on as well as the wiring hooked up wrong on either the alternator or the light. In any event, get the multimeter and start trouble shooting!

Kurt V
72 911E

J-70 · 08-31-2001, 06:06 PM

Hi again.

The engine is a 76, and the light is on at all rpms. I don't know the miles on the alternator and engine.

My brother has a multimeter and he told me that when the car is off, the voltage is at 12.5, but when he starts it, it drops to around 12.1

The voltage regulator has been fixed, and the mechanic said that the alternator is fine. The mechanic works for a shop that deals with porsches, imports and european cars.

Jason

pwd72s · 08-31-2001, 07:12 PM

Sure stumps me. Voltage drops with the engine running? Mechanic says alternator is good? Sure stumps me!
Any differences in that 12.1 V figure with varying revs?

[This message has been edited by pwd72s (edited 08-31-2001).]

pwd72s · 08-31-2001, 07:16 PM

By the way...Kurt, you are absolutely right. I'm decades overdue for the purchase of a multimeter? You have any favorites..in the "cheep" (Under $100) price range?

J Richard · 08-31-2001, 08:12 PM

Voltage drop with engine running = engine running off battery. (I am assuming 12.1v was at the battery) First place I would look is the transaxle grounding strap.

Next I would check the fender flares...

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93RSA

Roland Kunz · 09-01-2001, 02:33 AM

Hello

Maybe it is a wire loom interference caused by the newer engine.

Simple said did you run with two regulators ?

If the alternator was replaced and checked then it was hopefully runing with the regulator from the car.

Grüsse

Jim Smolka · 09-01-2001, 06:18 AM

Just a simple check first. Does the alt light com on with the key in the on position and the engine off?

Superman · 09-01-2001, 08:43 AM

If you have 12.5 volts at rest and 12.1 wiht the engine running, then your alternator is not returning electricity to the system. If the alternator is working fine, then there must be a problem in how it's wired into your car.

Some folks abovve are suggesting you make sure all ground wires and straps are clean, making nice connections. I agree. Some I think are also wondering whether your system is trying to run with two voltage regulators. That would be a bad thing. If there is a voltage regulator internal to the alternator itself, as in later alternators like in my '83, and there is also a VR near the engine fuse box, then perhaps two VRs are being used.

Clearly though, the car is running on the battery, and the alternator is not returning electricity to the system.

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'83 SC

Rot 911 · 09-02-2001, 02:07 PM

PWD, got my digital multi meter from Sears for around $50 to $60. It came in an impact resistant housing and has held up well to all the abuse I give it.

Kurt V
72 911E

pwd72s · 09-02-2001, 02:19 PM

Thanks Kurt. The Sears nearest us is in a mall where Cindy often shops. Next time she's looking at clothes? I'll be in the Sears tool dept.

Rot 911 · 09-02-2001, 06:55 PM

PWD, Sears has departments other than the tool department?

Kurt V
72 911E

pwd72s · 09-03-2001, 08:58 AM

Evidently they do. Cindy says so, anyway. Have to admit, I'm one of those guys who won't hang out near the bra & panty display racks. I feel more comfortable around the 3/8" drive ratchets, know what I mean?