1981 Targa SC not charging

[SanDiegoMike]

I posted previously about a cold start problem and at the same time noticed that the battery was not charging. When I turn the key before starting I do not get the battery light. When the car is on and the battery is not charging I still get no light. Another Pelican mentioned that a bad buld could disrupt the loop. Kind of strange but I am new to the 911 world. I had the alternator tested and all is good. Any thoughts? I will also continue searching prior post. Thanks in advance.

[timmy2]

In simple terms:
The alternator light is part of the voltage regulator circuit.
Did the shop test the regulator?
If yes, then the lamp may be burned out so the VR isn't getting a signal to tell it to get to work.

[SanDiegoMike]

You wouldnt happen to know the part number of the correct bulb would you Thanks for the info!

Originally Posted by timmy2

In simple terms:
The alternator light is part of the voltage regulator circuit.
Did the shop test the regulator?
If yes, then the lamp may be burned out so the VR isn't getting a signal to tell it to get to work.

[Bob Kontak]

Originally Posted by SanDiegoMike

You wouldnt happen to know the part number of the correct bulb would you Thanks for the info!

Mike,

No replacing bulb till the original is tested.

Sorry, those are the rules.

FYI - Open up the pdf file of all the parts and part numbers on your car via this link. Select your model and year.

Genuine Parts Catalogue - Classic Genuine Parts & Literature - Porsche Classic - Dr. Ing. h.c. F. Porsche AG

[Norm K]

Originally Posted by SanDiegoMike

... noticed that the battery was not charging. When I turn the key before starting I do not get the battery light. When the car is on and the battery is not charging I still get no light. I had the alternator tested and all is good.

You don't say how you know the battery isn't charging. Have you re-installed the alternator, post the "all good" testing, and measured the output at the battery terminals? Is the battery not charging because the battery won't take a charge or is it not charging because it's not receiving power from the charging system?

[SanDiegoMike]

Sorry about that. The alternator was removed and tested. It was reinstalled. The battery is brand new as of this weekend. The battery is not receiving power from the charging system.

Quote de SanDiegoMike

... noticed that the battery was not charging. When I turn the key before starting I do not get the battery light. When the car is on and the battery is not charging I still get no light. I had the alternator tested and all is good.

You don't say how you know the battery isn't charging. Have you re-installed the alternator, post the "all good" testing, and measured the output at the battery terminals? Is the battery not charging because the battery won't take a charge or is it not charging because it's not receiving power from the charging system?

[SanDiegoMike]

Thanks for the link Bob. I will pull the original bulb tomorrow and check it.

Quote de SanDiegoMike

You wouldnt happen to know the part number of the correct bulb would you Thanks for the info!

Mike,



No replacing bulb till the original is tested.



Sorry, those are the rules.



FYI - Open up the pdf file of all the parts and part numbers on your car via this link. Select your model and year.



Genuine Parts Catalogue - Classic Genuine Parts & Literature - Porsche Classic - Dr. Ing. h.c. F. Porsche AG

[timmy2]

If the lamp is good...
You should check the wire continuity from the starter to the alternator by connecting a voltmeter at Pin 14 of the 14 pin connector with the battery connected. Pull the 14 pin connector at the rear fuse panel and stick a probe in the #14 hole and touch the other probe to ground. you should see battery voltage.

Check and clean the power leads at the starter. that is where the alternator is connected to the main battery lead. (Where red meets black!)
Also check and clean the grounds at both the transmission to body strap and at the body to negative post strap. (Battery disconnected for all of this work)
Clean all the terminals at the 14 pin connector too.

[Bob Kontak]

Originally Posted by SanDiegoMike

Thanks for the link Bob. I will pull the original bulb tomorrow and check it.

Hi Mike,

I am hoping you get into the diagnosis of your fine automobile, vs part replacement. You will need time and a few tools to get it right.

A $3 bulb is not an issue. In fact, I would order another when you order the O2 relay under the seat. Although, you can get both at the local parts store.

I am not certain if the O2 relay is your running problem, but for chump change you can take it out of the equation.

Advise as to your level of DIY repair experience. I am pretty high as I have always had the guts to rip stuff apart but often have to rely on the guys here to help me put it back together after I eff it up. :-)

So I suggest, in this order, assuming you have basic tools.

1. Buy one of those $30 headband flashlights or a trouble light.

2. Buy a decent multi-meter. Not a $200 Fluke unless you are loaded, but spend $60-75. Watch a youtube video or two on how to use them. You will need the DC voltage function and the resistance function for starters and then when you are bad-ass you can start checking current (amperage) draw, for example, to test if your fuel pump is at the end of it's useful life. A new one sucks little juice, on old one sucks more.

3. Down the road...Fuel pressure gauges and an analog dwell meter. for checking fuel pressures and setting your A/F ratio.

Perform the task Timmy2 says. The 14 pin connector is on the bumper side of the rear fuse panel. Get your reading glasses on and you can find the #14 cast into the connector part. Check if voltage is making it there.

[Bob Kontak]

Originally Posted by SanDiegoMike

I posted previously about a cold start problem

You don't have a cold start problem, you have at least only a cold running problem. Your car starts = no cold start problem.

[SanDiegoMike]

Following the advice of others I tested the bulb instead of replaced it. It was fine. I also got a non "harbor frieght multimeter". Following Timmy2's advice I opened up the back to get to the 14 pin connector which is where I found what you see in the pictures. In the panel there was a light that was sticking threw a hole the PO had drilled. When I opened up the panel I saw that it was taped and stuck into the plug pictured. The other loose plug had a question mark on it. I manipulated the light and found that the light came on. I had a friend check and found that when this light was on the battery was charging. When the wire was moved and the light was off the battery was found to not be charging.

Originally Posted by Bob Kontak

Hi Mike,

I am hoping you get into the diagnosis of your fine automobile, vs part replacement. You will need time and a few tools to get it right.

A $3 bulb is not an issue. In fact, I would order another when you order the O2 relay under the seat. Although, you can get both at the local parts store.

I am not certain if the O2 relay is your running problem, but for chump change you can take it out of the equation.

Advise as to your level of DIY repair experience. I am pretty high as I have always had the guts to rip stuff apart but often have to rely on the guys here to help me put it back together after I eff it up. :-)

So I suggest, in this order, assuming you have basic tools.

1. Buy one of those $30 headband flashlights or a trouble light.

2. Buy a decent multi-meter. Not a $200 Fluke unless you are loaded, but spend $60-75. Watch a youtube video or two on how to use them. You will need the DC voltage function and the resistance function for starters and then when you are bad-ass you can start checking current (amperage) draw, for example, to test if your fuel pump is at the end of it's useful life. A new one sucks little juice, on old one sucks more.

3. Down the road...Fuel pressure gauges and an analog dwell meter. for checking fuel pressures and setting your A/F ratio.

Perform the task Timmy2 says. The 14 pin connector is on the bumper side of the rear fuse panel. Get your reading glasses on and you can find the #14 cast into the connector part. Check if voltage is making it there.

[SanDiegoMike]

I stopped there trying to figure out the light and plug to nowhere before moving into the 14 pin connector.

[Flat6pac]

The 3 wire plug is a voltage regulator plug which you dont have on the control panel. So, you should have a Paris-Rhone (Verlo) alternator. It will have an 8 mm allen hole on the center of the alternator shaft and has an on board voltage regulator on the back.
The back of the alternator will have 3 wires connected with the black wire taped off that was used when the VR was on the control panel.
Bruce

[Flat6pac]

The green wire is the distributor wire. Plugs in and a clip retains it.
Bruce

[SanDiegoMike]

Thanks for the ID. Why do you think they had the light jumpered to it?

Originally Posted by Flat6pac

The 3 wire plug is a voltage regulator plug which you dont have on the control panel. So, you should have a Paris-Rhone (Verlo) alternator. It will have an 8 mm allen hole on the center of the alternator shaft and has an on board voltage regulator on the back.
The back of the alternator will have 3 wires connected with the black wire taped off that was used when the VR was on the control panel.
Bruce

[timmy2]

Somebody has done some unique wiring modifications to your car...
Can you post a picture of where/how the light hooks up to the original alternator plug to get it to light up?

Interesting that the original distributor green wire has been bypassed.

Did you take any pictures of the wiring connections at the alternator?

Take a bunch of pictures of the harness wiring in the rear panel area, should be able to figure out what has been done and how to get it back to normal....

I'm thinking they disconnected the alt light from the circuit and put the one you found in there instead.

Hope you are up for some wire tracing...

[SanDiegoMike]

So now that you say that I am back at the gauge and bulb. There is an upper and lower red light. Pardon my newness. The upper has no bulb or wiring going to it at all. The lower, with a G surrounded by a circle has a bulb that test good. Is the upper red light the alternator/battery light?

Somebody has done some unique wiring modifications to your car...

Can you post a picture of where/how the light hooks up to the original alternator plug to get it to light up?



Interesting that the original distributor green wire has been bypassed.



Did you take any pictures of the wiring connections at the alternator?



Take a bunch of pictures of the harness wiring in the rear panel area, should be able to figure out what has been done and how to get it back to normal....



I'm thinking they disconnected the alt light from the circuit and put the one you found in there instead.



Hope you are up for some wire tracing...

[Bob Kontak]

Mike - nice job so far. Some things are a little weird, but suspect we can get it straightened out.

The green "?" wire is profoundly important. It has to be bypassed with another similar function wire.

It is the wire from the distributor to the CDI box that tells it when to fire a spark. Car cannot function without it.

Here are some pics of where it plugs into the dist. The hole is where it goes.



Here it is plugged in.

[Bob Kontak]

Originally Posted by timmy2

Take a bunch of pictures of the harness wiring in the rear panel area, should be able to figure out what has been done and how to get it back to normal....

I'm thinking they disconnected the alt light from the circuit and put the one you found in there instead.

Hope you are up for some wire tracing...

Do this, Mike. We can help you.

[timmy2]

Pelican Parts - Porsche 911 Parts Listings & Diagrams
Download the '78 and the '82 diagrams from the link above and print them out. they will help.

The lamp for the alternator should have a blue wire and a red/black wire to it. The top lamp on my car is for the oil pressure idiot light and says OEL below it. It should have a green/white and a red/black to it.

Use your ohmmeter and a long wire jumper to extend one lead and connect the blue wire at the bulb in the gauge, to the blue wire in the 3 terminal connector and see if there is continuity (very low ohms)

I'm beginning to think someone used a lamp instead of a resistor to modify you charging circuit when using an updated alternator.

Read this thread, especially the post by Early_S_Man to understand what I mean.
Converting to new stile alternator Help!
Here is the resistor you need for the mod:
ACS 5s 1R J T&R Arcol | Mouser