1974 1.8L not holding a charge, Causes other than alternator Options

[Robnxious]

I have tried digging in on this a bit on here searching, and have seen posts saying "make sure it's the alternator before replacing". Here is what I have found so far. When the battery has a full charge, the volt reading is 12.75, and when it's running, it's about 13.5 (I remember reading on here last night that the running voltage should be about 14.5 IIRC). Which tells me it SHOULD be the alternator (that and the fact that if I run it with lights on at night, it needs charging when I get home). Also, my battery charger has an alternator check function and it said it was bad.

But, I also did the old shade tree mechanic trick of disconnecting the negative battery connection when the car was running, and it didn't miss a beat, still idled strong.

I do have an alternator that I bought (yeah I know, didn't see the threads saying "make sure it's the alternator before buying" until after I had ordered it), but seeing how this is a PITA job the first time, I am hoping I can get my new baby up and running easily.

Any help is appreciated, and thanks in advance

[larryM]

When the battery has a full charge, the volt reading is 12.75, and when it's running, it's about 13.5 (I remember reading on here last night that the running voltage should be about 14.5 IIRC).

if I run it with lights on at night, it needs charging when I get home).

I also did the old shade tree mechanic trick of disconnecting the negative battery connection when the car was running,

normal alternator output is 13.8-14.2v - that would generally be tested "off-idle"

normal alternator output

how to test alternator

on-car alternator test

what is your volt reading when running with lights on? - likely less if it won't recharge the batt

BAD idea to disconnect alternator with engine running see
alternator woes - google

[TheCabinetmaker]

No on the 14.5. I suggest a battery terminal cleaning. Including the negative cable to body post, and also the ground strap above the trans.

And Larry is right about disconnecting the cable while running. That's an old trick for an old generator.

[Robnxious]

normal alternator output is 13.8-14.2v - that would generally be tested "off-idle"

normal alternator output

how to test alternator

on-car alternator test

what is your volt reading when running with lights on? - likely less if it won't recharge the batt

BAD idea to disconnect alternator with engine running see
alternator woes - google
[/quote]

Thanks for your quick response. To answer your question, I went out and tested it.

*Started it up, was at 13.3 running.
*Turned on Lights, went to 12.75, and then started dropping rapidly. After less than 1
minute, it was down to 12.4
*Turned lights off, popped right back to 13.5 instantly and stayed there
*Decided to test it with lights off, but turning the radio on. Stayed at 13.5

It looks like I have a simple solution here (just don't drive at night! (IMG:style_emoticons/default/smile.gif) ) Seriously though, I have ZERO time in working on these, and am not a trained mechanic, nor have I done any major projects on cars except for replacing items, but to me it seems that if I am running the radio, the power should drop if the alternator is not running, or after it dropped w/ the lights on, there should have been a slight drop when they were turned off, not an increase.

I do have someone up here who does fantastic work and is a board member (Ron Kain of IPB Autosport, who did the inspection on it and who I had told that the alternator was bad, so it's not a mechanic who diagnosed it, it was me) but what's the fun of owning one of these if you aren't willing to wrench on it yourself?

[Robnxious]

No on the 14.5. I suggest a battery terminal cleaning. Including the negative cable to body post, and also the ground strap above the trans.

And Larry is right about disconnecting the cable while running. That's an old trick for an old generator.

Thanks, I sent him some stats re: his answer, feel free to add anything to that. The battery connectors are clean and pretty much new. I will clean the ground strap above the trans. I have the feeling that hasn't been done in eons

[TheCabinetmaker]

Those readings are normal. If your battery its running down with the lights on its probably not taking a charge.

[Frankvw]

Could this not just be a bad battery? Not charging properly and using up the power when in use... Have your battery tested to rule this out. The battery places can test this pretty easy and most of the time as a free service...

[Robnxious]

Could this not just be a bad battery? Not charging properly and using up the power when in use... Have your battery tested to rule this out. The battery places can test this pretty easy and most of the time as a free service...

Brand New battery too, which leads me to believe it had had a problem starting before and they just thought the battery was bad and replaced it.

[rhodyguy]

Don't forget the ground post forward and below the engine relay board.

[porschetub]

13.8 is the norm,but I noticed my new regulator is marked 14.4volts??,not sure what the original ones supplied from the factory were,you would presume the same.
Surely if the OP has good battery and earth contacts (and new battery) you would think the regulator is at fault,strange that it is still making above battery voltage with no load however.
I have rebuilt many altenators and played with charging systems in many cars over the years but it amazing to me some of the weird shit that can go on......

[ottox914]

I'd agree with checking all grounds, battery, trans strap, the multi-lug ground on the engine, by the relay board, and load test the battery- not just a check for voltage with a meter. Made that mistake once- checked with a meter and had great voltage at the battery, but when load tested, the battery was no good. Wasted a fair bit of time looking for the answer when the problem was an easy one to fix, and was right in front of me.

[pbanders]

Follow through the tests on this link, it's the best reference I've found.

http://www.ratwell.com/technical/ChargingSystem.html

[Root_Werks]

Others have asked it and I don't see the information in the previous posts:

Does the battery drain overnight? As-in, just sitting without the car running.
Is your 914 still L-Jet (if it is, there are other things to check)

[Robnxious]

Others have asked it and I don't see the information in the previous posts:

Does the battery drain overnight? As-in, just sitting without the car running.
Is your 914 still L-Jet (if it is, there are other things to check)

No, the battery does not drain over night, yes and it's still L-Jet

[TheCabinetmaker]

So, the battery only runs down when driving with the lights on?