New owner: where the voltage regulator on my '74

[steve meltzer]

Just purchased a '74 Carrera, after a nearly 18 year hiatus from these great cars. The alternator light won't go out until 5-10 minutes of driving have passed. The battery, at rest, only reads 11.89, and with the car at idle or even revved to 3K or so, the VOM only shows the battery at 11.46. I suspect that the alternator is bad, but I just realized I should also check the belt tension, which i will do. Nonetheless, I thought the VR was on the left inside engine bay, but maybe it's internal to the alternator. Where should it be, if it were there? (I assume that fuses live in the black box, on the left side, with the two wing nuts. I didn't remove the wing nuts as I was in a hurry. I doubt it's in there.)
Any other things I should consider? Any hints on doing the R&R for the alternator? thanx steve

[rwest]

Lots of other stuff under that panel, relays, rear window defroster relay etc., can't remember for sure it the VR was under there in my 77, but I had an external one until my alternator "gave up the ghost" and the new style is internal.

Short story, you could have either type on your car.

[timmy2]

Take off the wing nuts and look. If original it should be there beside the CDI box.

[Zaz]

There is an external mount for the VR next to the CDI, but many (most?) have been upgraded to internal over the years, so you may want to pull the alternator to confirm, as well as to check those connections/grounds. When mine started getting jiggy I took it to a reputable local rebuilder, and beefed up the ground strap termination to the case.

[timmy2]

No way will I "update" from remote to internal VR unless I decide I need a much bigger output for electric A/C.
So easy to change the VR when it failed mounted on the panel compared to pulling the fan and alt. The original alt in my car is rebuilt and should last a while.

[steve meltzer]

Thanx guys. i'll check to see if the VR is in there. Belt is tight. How do you differentiate between a bad alternator and a bad VR? Also, being new to this site, does it not automatically notify you when someone has joined the discussion? thanx again. Most appreciate the help. steve

[ossiblue]

Go to the top of this page and look at the bar just under the orange box with the pencil icon. Look to the right and you will see blue boxes. Click on the one that says, "Thread tools." In the pull down menu, click on "Subscribe to this Thread." Now, when someone adds something, you will be notified, via email, I believe. I've only used it occasionally so I'm not quite certain, but you will be notified.

[steve meltzer]

Ossiblue, thanx so much. i actually found that button just before submitting my last post. much appreciated. steve

[timmy2]

Now you know where it is so time to troubleshoot.
Your battery voltage is very low at 11.5 volts.
Put it on a charger and get it up to 12.5 volts resting. If it won't hold that level of 12.5 or so for a few hours then have your battery tested. (May have a bad cell and the alternator can't fix that)

Then once you know you have a good battery monitor the charging/running voltage. Should be 13.5 to 14.5 if all is normal. Spikes up to 18 volts means the VR is suspect.
Could be the alternator internals as well, but get the battery up to normal charge levels and see what is going on first

[steve meltzer]

Timmy2, thanx for the idea. I must admit i thought of that, but I thought that the failure of the alternator to raise the voltage with the car running (no matter what it was) proved a faulty alternator. thanx steve

[steve meltzer]

oops...I forgot to post that it is an Optima battery. Wonder if that might make my VOM conclusions about a bad alternator invalid?? Anyhow, on the slow (2A) charger now. results tomorrow. thanx. s

[timmy2]

Good luck charging the Optima. They can be difficult at times.
Make sure it is fully charged.

[steve meltzer]

OK, 12 hour slow (2A) charge = excellent, 12.5 on the battery. Therefore, it's good, but, with the engine at about 750 RPMs, the red warning light remains on and VOM shows battery loss at 12.2V. Ergo, it's a bad alternator, right? My previous experience says not to drive the car until this is repaired. right?

I want to put aftermarket AC on the car, so I can drive it in Houston. Best way to upgrade the alternator for this while it's out??

thanx steve

[timmy2]

May not start to charge at only 750 rpm. Mine won't initially kick in until around 1200 rpm.
Need to check output at 1500, 2500 and 3500 etc. (driving RPM's)

[steve meltzer]

let me drag my wife out there to rev it up while i run the VOM. any thoughts about a need for increased amps with an add on AC? thanx. s

[steve meltzer]

OK, no go. even at 3K the VOM reads about 12.2 or so. Of course the red alternator light didn't go off. Time to move on to an R&R, right? thanx steve

[timmy2]

You never said if you found your VR under the rear fuse panel cover.
If it isn't there, then it's R&R time for the alternator.
Maybe take the fuse panel cover off and post a picture.

[steve meltzer]

Thanx again for your help and interest. l'll look tomorrow and let you know. Doubt that's the culprit, but....steve

[timmy2]

If your VR is the original metal box with electromechanical parts inside, it can seize up and fail.
Popping in a $50 electronic one is a lot easier than pulling the alternator.
Always good to know what you have in there as well.

[steve meltzer]

Well, i was sure I could recognize a VR, but I'm not sure. One of these looks like a relay, the other, a part of the CDI unit. So, you would replace the VR, assuming it's there. Right? Is this part available from Pelican? I would assume so. thanx steve