Sorry more questions: alternator voltage all over the place

[sproggy]

I posted earlier that my ammeter is suddenly way in the plus side...and bouncing around. I opened up my regulator and it LOOKS fine. Not gummed up and the bar moves freely. No signs of any burning. It's not particularly old but perhaps it got fried internally. I read all Rudi's stuff but in the field it's not so easy to test. Cleaned all the contacts and ground. In testing the alternator, I put my voltmeter to the B connector and voltage is fluctuating ALL over the place from 16 to 4 to 8 to 13 to 15 to 14 to 7 etc.... All in the matter of 5 seconds. What the hell does THAT mean? Variety is the spice of life? I'm assuming it means it's fried in some way, and this also makes sense that the ammeter is bouncing all over.

Or not....?

 

[coonassjohn]

It sounds like a short somewhere in the wiring, or a loose ground connection somewhere.

 

[bj40green]

Here is how it works.
The VR (ign terminal) looks at the voltage from the ignition key.
If the voltage is below 13.6V the VR sends that same voltage to the F terminal on the alternator which tells the alt. for max output.
When the voltage on the ignition key is higher then 13.6V the VR drops the voltage on the F terminal so the alt. lowers the output to trickle charge.
When the voltage on the ignition key reaches 14.8V the VR output (F) goes down to zero (=battery is FULL).
Now..... when the voltage from the ignition key is fluctuating for what ever reason, the VR (F terminal) follows and the alt. follows.
When you have bad contacts in the wiring between the F terminal on the VR and the F terminal on the alt. you have the same problem.
Solution: check if the voltage on the F terminals (VR and alt) are jumping. This means a bad contact / connector.
Check if the voltage on the IGN terminal on the VR is jumping. If so..... tap your ignition switch or wiggle your key to see if the behavior changes.
NOTE: this is the chicken and the egg problem. It's a closed circuit and at several points it can go wrong. Even a bad contact in the fuse block can cause this problem.
PATH: battery -► fusible link -► fuse (block contacts) -► ignition key -► IGN terminal on VR -► F terminal(s) from VR to Alt -► battery output -► circle is closed.

Rudi

 

[sproggy]

Thank you, Rudi. I have cleaned all the contacts on the fuse block and VR and have taken apart the VR and run a little 1000 grit paper over those contacts inside though they were super clean (VR is only a few years old and has seen very little use). I tried my best to clean on the alternator, too. How can I clean the contacts both on the harness plug and on the alt for the F and...is it E? input? They are a little crusty. I will say my fuse block is pretty gnarly looking after near 50 years. It's sort of coming apart. I wonder if that's an issue though checking the voltage there did not reveal any jumping or fading out.

Could it be the ammeter itself causing this? I know it's a pretty simple mechanical device, just two magnets if I remember, and I can't see how this would cause the bouncing but rather be subjected to the bouncing caused by something else. So the VR is bossing around the alternator but what is it in the alternator that is actually changing the output? Couldn't this part go wonky?

With my voltmeter, I am touching the F contact on the VR with the plus probe and touching ground with the negative probe, correct? This is all running engine...does it have to be at 2000 rpm?

And I am unplugging the F/E harness from the alternator and checking the F contact with it unplugged, engine running?

I didn't realize the alternator was getting the juice from the F. I thought it was from the B but thinking it through, of course. And it is of course MAKING power so it does not need to receive a lot of juice to do it's job. And then the B is bringing all the juice back to the battery.

I do not have a fusible link anywhere. Was this stock on a 1971? Do I need to put one?

Tap my ignition switch...I don't know what you want me to tap here...my ignition key cylinder?

I did run the truck for about 20 seconds with the F/E plug out of the alternator, by mistake. I thought I had solved my problem as the ammeter was resting where it usually does and was completely steady. Then I realized the plug was out. However, in retrospect, does this show the the fault is not between the alt and the ammeter but between the ammeter and the alt since?

Your PATH at the bottom of your message doesn't include the ammeter. What am I missing? Is this not part of the path? It is after all getting the full juice from the....hmmm, from the battery or from the alt??

I'm feelin' electric!

 

[bj40green]

You have to look for a bad / intermittent contact. That can be a connector, a connection, loose wire on the back of the Ammeter, bad ignition switch, anywhere in that circuit and can be a pita.
Yes, the Ammeter is part of the circuit. The current through the Ammeter goes 2 ways and tells you charging or discharging.
If the voltage on the F terminal on the Alternator is steady, the output voltage on the B terminal should be steady. If not.... your alternator is up for inspection which is very unlikely. Even the VR can be the problem. It's a matter of elimination.

Rudi

 

[sproggy]

Well back to having at those contacts and connectors. Thank you, Rudi.

Sproggy

 

[bj40green]

Sproggy, here is a red neck solution:
Disconnect the VR.
Run a wire from F VR to F Alternator.
Run a small wire from the battery positive to IGN VR.
This way you eliminate the whole wiring circuit from battery, fuse, ammeter, ign switch etc.
In other words; you hook up the VR directly to the alternator.
If the problem is still there..... it's your VR. If the problem is gone..... you know what to do.

Rudi

 

[sproggy]

Hey Rudi...ooo I like that! I'll give it a go in the morning! I noticed what seemed like an odd thing yesterday. In testing the VR and alternator, when I used the negative post on the battery as a ground, the voltage fluctuated all over the place. But not so or less so when I used the engine block as a ground. Does this make any sense? I will add that it was not always easy to make good contacts so I was unsure if the fluctuations were caused by the system or my bad connections.

The plot thickens: I did have a short recently and perhaps twice. My unused choke cable that just flops around in the engine bay, more or less, managed to make contact with the electrical connection on the automatic chock mechanism on my Weber carb.....this connction comes from the positive side of the coil and of course the choke cable will be grounded with the body. It started smoking and I grabbed it off and cursed and secured the cable to the firewall. Later when I was driving the car I noticed the ammeter not in it's normal place and realized I had a blown fuse. Once I replaced it, all was fine. A few days after that I replaced my brake booster and had to move this cable to do so. Working on the electrical issue yesterday, I realized I had not re-secured it and in fact found the end of the cable burned off and still sitting next to the carb. I believe this was from a second instance of this thing shorting out although it did not blow a fuse this time. Perhaps it instead fried the VR or...?

I will try your fix tomorrow. Thanks

Sproggy

 

[bj40green]

when I used the negative post on the battery as a ground, the voltage fluctuated all over the place. But not so or less so when I used the engine block as a ground

Time to check the ground cables.

Rudi

 

[sproggy]

Well I don't know what happened..... I cleaned as many contacts as I could. All VR contacts, NEW alternator, cut new battery cables and cleaned all the contacts. Sanded fuse block contacts. Opened up VR again and saw nothing, dropped some screws on the ground. Closed it back up. DId some other crazy stuff I can't really remember. Voltage was still all over the place and would slowly climb at idle (reading from B) from 12 slowly to 16.
I moved onto the redneck method, screwed it up, shorted something, read your instructions again and came up with a different interpretation and tried that. No shorting as this time I didn't try to plug E into the positive battery terminal. Said giddyup and got the horses galloping. Voltage at B was still climbing from 12 up past 15 and ammeter nervous. Turned the key off but truck didn't shut off. Pulled the lead going to VR IGN off the positive battery terminal and the engine died. Pulled the Redneck Method wires off and tried the truck again. Everything back to normal. Ammeter calm and not jumping. Voltage from B around 14 if I remember...fluctuating a little which I recall is kind of normal but not climbing to 16 and not dipping to 7. So....I don't know what happened.
I'm not too upset to have a new alternator as the old one was developing some rust inside and I don't imagine that's so great. Got a new VR coming in the mail but that will be good for a spare.

Rudi, what do you think was going on? I will say, I spent a lot of time trying to ground my volt meter on the intake manifold and suddenly thought maybe that's not so great as it was quite hard to maintain a ground. I had a lot better luck using the valve cover hold down post/bolt. So I might have been my own worst enemy there but grounding on the battery was showing crazy fluctuations, too. And the ammeter was jumping around all the time so something was up. It wasn't just me

I'm curious. The E (ground) to the VR...where does it originate...from where is it pulling the ground? I could not trace that white wire with the black stripe.

My white with red stripe VR IGN wire is attached to the bottom position on my fuse block. Is that correct?

I had a thought while doing this. I rather think of the ground wire almost as an afterthought. I know I need it but in my head...the POWER source is vastly more important. You gotta have power! I realized this is wrong. The ground is every bit as important, in fact, perhaps better to think of it as NEGATIVE POWER. As we all know, you need both the + and the -. Each is useless without the other. I've been doing the ground a disservice all these years. I only bring this up as I wonder if some other crappy mechanics like myself might have this same issue. We make problems for ourselves by not thinking of the ground as equally important as the power source.

So, Rudi, what do you think was going on? The only thing I can conjure is that even though I had taken apart the VR and all the wires off and polished all the wire fittings and connection posts, somehow there was still not a good connection. When I took it apart a second time and reattached everything, perhaps that time it DID get a good connection. The second time I had it open I did spin back and forth a bit the paper wrapped cylinder (dynamo?) noting with surprise that it spun and was not firmly anchored. Is there something to this?

Thank you!

 

[bj40green]

Congratz! But from your story I can't tell you what exactly solved the problem.
The VR is grounded by it's housing. The same goes for the alternator. Both are connected to each other via the ground cables but not directly to each other because the VR is on the body and the alt. is on the engine and the engine is connected via a cable to the frame and battery. To prevent a potential differential between ground VR and ground alternator Mr. T added a ground wire (W/B stripe) between those two (E vr and E alt.). This E wire is the counterpart of the F wire. F is the + voltage and E is the ground. Clear as MUD ???????
Anyway, the problem is solved for now. Let's hope it stays that way.
Right now I'm in the middle of a packing and moving job (we sold our house) so I'm not on Mud for the next 3 or 4 days.

Rudi

 

[sproggy]

Congratz! But from your story I can't tell you what exactly solved the problem.
The VR is grounded by it's housing. The same goes for the alternator. Both are connected to each other via the ground cables but not directly to each other because the VR is on the body and the alt. is on the engine and the engine is connected via a cable to the frame and battery. To prevent a potential differential between ground VR and ground alternator Mr. T added a ground wire (W/B stripe) between those two (E vr and E alt.). This E wire is the counterpart of the F wire. F is the + voltage and E is the ground. Clear as MUD ???????
Anyway, the problem is solved for now. Let's hope it stays that way.
Right now I'm in the middle of a packing and moving job (we sold our house) so I'm not on Mud for the next 3 or 4 days.

Rudi

Yup, clear as MUD. It's called the Ghost in the Machine, innit? Happy moving and thanks for your help. I have been doing the same thing with my fathers house....been taking forever and a day.

Cheers....

 

[Past it]

Having read it all ,I now know much more about alternators and voltage regulators. But not enough! I have a bj42 1982 24volt (see bj42 found in a derelict barn). My ignition / filter light remains on when engine running, no response on ammeter and battery runs down so seemingly no charging from alternator. I have a 6 wire external VR (brand new )and by opening points on one relay (filter/ignition relay), ignition light goes out. If this relay were functionig correctly it should also energise the second relay and control the field ( F terminal) on alternator. The volts on F is bouncing all over the place.Terminal B on alternator reads a steady 25volts ( when battery charged up). Terminal N from alternator (feed to ign. relay) appears to be open circuit but very unreliable readings. My questions are, (1) is it necessary to earth terminal E on top of the alternator as the top plate looks to be insulated ( I have earthed it to the chassis with no noticeable response), and (2) how do I check that the alternator is giving the correct output or even any. My guess is to unplug 3pin plug on alternator and feed in 24 volts from B, increase engine speed, and monitor output on B alternator terminal. Bit reluctant having read so many disasters with wiring burn outs etc. Any tips ?

 

[sproggy]

That set-up is above my pay grade I'm sorry to say.

 

[Past it]

Thanks Sproggy for even looking. I am getting desperate. Further checking shows my new 6 pin regulator only has 5 wires connected. The sixth pin is just not there. The sixth pin on the wiring loom however has a fat white cable connected to it and I am sure it has to do with starting the regulator process. Taking the plunge I connected the fat white from the loom to the vacant 6 pin on the regulator. Result? Relays clicking all over the place with ignition key removed. Only one option. Remove plug before smoke appears and start crying, again. ---------- I am trying to eliminate the alternator from my search but not sure how to test it. With the alternator 3 pin plug removed can I simply apply 24 volts from the battery into the F (field) pin , rev up and monitor the B output on the alternator? Help someone!

 

[sproggy]

How about pulling the alternator and taking it to a shop to test it? They supposedly do it at parts shops here in the US. If it's not the same in the UK, I'm sure you can find an alternator/auto electric shop via internet and take the alternator there for checking. That would at least eliminate a bad alternator. While you're at it, bring your new VR to test, too. Supposedly, they are sometimes bad out of the box. Did you post this in the main forum, too? I mean, not only in this thread? There probably are not many folks following it.

 

[Past it]

Thanks Sproggy, you're right . I havn'ttried the main forum. My computor connection is crap so I have to delve in when and where I can. There are so many threads on this subject but have yet to find the appropriate one. Off to the main.