Early 944 Charging Problem... Alternator is good! Need Help!

[x2nervisx]

Ok so I have an 83 944. It starts up fine and stays running until the battery drains. For some reason the battery is not charging.

What I've done so far:

- Cleaned the grounds with my dremel tool in the front passenger and driver's side headlight area.
- Replaced the negative battery cable with a brand new one and also sanded down the contact points.
- Replaced the cable that grounds the chassis to the rear of the engine block.
- I sanded down the contacts on the alternator AND the starter.
- The battery light DOES illuminate and stays on the whole time.
-I've already replaced my alternator with another used one and a NEW voltage regulator and had that bench tested at an auto parts store and it passed all tests. I've actually tried 3 different used alternators with the same results.


With all that done, I still get 12.3 volts when i read across the battery and when I put my voltmeter directly to the alternator, I get the same readings. Increased RPMs do not help. What else should I be looking for? I'm at a loss right now and this is the only thing holding me back from restoring my 944. HELP!

[krystar]

so you're saying your alternator is not actually providing the engine with enough electrical power to self sustain? realistically, once the engine is started, the battery can be unplugged completely and engine will keep on running.

alt belt is tight right? the pulley is spinning?

[x2nervisx]

belt is tight and the alternator is spinning fine. No noises at all.

[zedsn]

You could have a battery draw this is pulling the voltage away and not letting the battery recharge. My 83 had a drain and I was able to isolate a batch of 3 wires that went to the battery positive terminal with a switch in the cockpit. Not the best way but an easy fix for me at the time. Try to take a digital volt meter on the + and - terminal with the ignition key out and see if the voltage drops a small amount every couple of minutes. If it stays the same and doesn't drain down you have a different problem.

[Rasta Monsta]

12.3 volts does not a good alternator indicate, padawan.

[944 Ecology]

Yep, either take all three alternators to autozone and have them test them, or spend a few bucks and buy a rebuilt alternator.

In other words, you have three bad used alternators.

[x2nervisx]

The alternator on the car now is the one I just had bench tested at pep boys.

The test results are as follows:

lamp/diode trio - Passed
regulator test - passed
rectifier test - passed

battery volts:
Low - 13.50
Actual - 14.17
High - 15.40

[matthewb]

You might try checking for a short in the wire that goes from the dash light to the alternator. Should be a blue wire that runs out along with the starter signal wire. If that is shorted somehwere then it will make the light light up and will not allow the alternator to turn on.

You would need to have a pretty serious draw somehwere for the draw to pull down more than the alternator could put out. I would hazard to say that you would be starting a fire somewhere if that were the case.

How much of a restore did you do on this vehicle? You could start by disconnecting that blue wire on the alternator end and turning the car to run, if the alternator light is lit up there is likely a short somewhere in that wire. The light should not light up if it is not connected to the alternator.

Good luck

[x2nervisx]

Originally Posted by matthewb

You might try checking for a short in the wire that goes from the dash light to the alternator. Should be a blue wire that runs out along with the starter signal wire. If that is shorted somehwere then it will make the light light up and will not allow the alternator to turn on.

You would need to have a pretty serious draw somehwere for the draw to pull down more than the alternator could put out. I would hazard to say that you would be starting a fire somewhere if that were the case.

How much of a restore did you do on this vehicle? You could start by disconnecting that blue wire on the alternator end and turning the car to run, if the alternator light is lit up there is likely a short somewhere in that wire. The light should not light up if it is not connected to the alternator.

Good luck

i'll try disconnecting the blue wire tomorrow and seeing what happens.

[kfray]

Check the cable from the alternator to the starter, this is the charging path:
Alternator to Starter to Battery positive terminal.
With the engine running the Battery voltage should read between 13.5 and 14.5 Volts DC if the Alternator is charging
http://www.pelicanparts.com/944/electrical/944_84_1_1.jpg

[AA_Ezra]

Ok, maybe the person who mentioned to this me will chime in but... if i remember correctly if the blue wire connections has some sort of diode or maybe its the dash light that has a diode. Either way if one of those things is damaged it does not let the alternator work correctly.

But i also suspect that it may be the voltage regulator which only runs a few buks

[x2nervisx]

I replaced the voltage regulator before I put the alternator back in.

[John_AZ]

Have you checked the resting battery drain while the car is sitting?

Disconnect the POS cable and put an ammeter between the post and wire.
Set your guage at a high amp reading and move down to ma=milli amps.

I get about 9.0ma drain +- on both cars.
Clarks says you can expect up to 65ma but that is way too much.
Excessive Battery Discharge Rate



If the drain is "normal", get a battery hydrometer and check the specific gravity.
If the cells are low----get a new/remanufactured alternator

I just replaced and alternator that had a running charge of 13.9V. I did all the steps you have done. It did not keep the battery charged.

The Bosch remanufactured did. BTW, a remanufactured alt is a lot better than a rebuilt and will last longer.

GL
John

[HondaDustR]

Yeah, sounds like it could be the exciter wire. It's pretty simple on the early cars. Just a wire from the ignition switched voltage, through the charge light, and to the small alternator lug. With the key on, car not running, wire disconnected, you should see battery voltage on the wire at the alt and it should light the charge light if you touch it to ground. If the light stays on with the wire disconnected, then there's your problem.

Do the tests at the parts stores actually put a significant charging load on the alt? My rebuild from a local shop came with a test pass sticker for 105A.

[Arizona_928]

My N/A has the exact problem.... I've been fiddling with the blue wire forever.
Have even replaced all of battery/alternator wiring. Interested to see what is causing yours.

[x2nervisx]

Battery is good. After doing some research, could the factory alarm be preventing the alternator from charging? I just noticed that when I turn the key on, i can hear the factory alarm box clicking (the horns don't work so i assume the clicking would mean the horns going off). I don't have a key for the alarm and i also noticed that the wiring was disconnected from the key hole for the alarm anyway. I've read in somebody else's thread that he was able to start his car with his alarm brain removed but it prevented the alternator from charging his battery. I've already researched how to disable the factory alarm but every single post i've read deals with the later style alarm. I haven't found anyone that has disable the factory alarm in an early car. I've tried the clarks garage method but the alarm relay still clicks when i turn the car on. Is there a definitive way to disable the alarm on an early car?

[mxfrank]

This is what the back of a typical (not necessarily Porsche) Bosch alternator looks like:

http://www.coolcatcorp.com/faqs/LucasBosch5.jpg

The D+ lead is used to "excite" the alternator field at start up. If it's not getting current, there will be no charge. This terminal is wired in series with the dash warning lamp. If the bulb is blown, there will be no current at D+. The first thing I'd do is disconnect the lead and attach a voltmeter between the wire and a good ground. Turn the ignition "on". If you don't see voltage, the problem is in the dash light circuit.

[Rasta Monsta]

To add to the above, you can also disconnect the exciter wire, jump directly from the big lead to the exciter post, and then check your voltage.

[earlr85944]

Hi Greg, this is Rich, I figured the first alternator was good as it came off a good running car. I think you are on the right track looking at the alarm, that did actually happen to me where my car would not start unless the alt belt was removed, it turned out to be a bad alarm module. Your situation is a little different but you are correct in that the alarm is activating, get that fixed first. On a previous 944 I was able to pull the plastic vent from the inside door pillar and remove the clip behind the alarm key switch and then manually disabled it, otherwise jump it out the module, dont have the procedure off hand.

[x2nervisx]

Hey Rich. Turns out my first alternator was good in the first place! I'm in the midst of getting this all sorted out now with the alarm. But with the trying to start the car several times a day, I think I broke the starter. Do you have another starter for sale?