S4 Alternator Woes

[hubrick]

Hello All,
Well, I didn't get many miles on my Elan after 4 weeks of electrical repairs. I decided to check my tire age before getting on the highway for any distance, and there were 3 digit codes ending in 7, so 1997 or 1987. Thanks to the list, found Maxxis TA-202's, got 5, blasted and painted the wheels, and after a couple of weeks I was out on the roads again. Until Sunday. Went out for a 30 minute drive with the aftermarket electric fan on all the time (for some reason the thermostat function has failed). Stopped to swap drivers, and it didn't have enough juice to start again.

Here's what I have:

I've read many threads about alternator swaps for a S4 car, I believe I have the 17ACR Lucas alternator in my car (pictured, I presume that from reading other posts). I don't have the wires at the solenoid that I read somebody describe for a S4 car. One brown wire that either goes to the control box (as per the S4 wiring diagram) or a connector (picture) mounted on the left engine bay frame rail. The big wire from the alternator goes in here and two big wires come out - presumably one to the starter solenoid and one to the control box.

Ignition light comes on with the key, flashes dimly at idle, and goes out at higher RPM - before and after the alternator quit charging.

I have a +2 S130 wiring diagram from Phil that shows the solenoid with 3 brown wires, but I only have one - the other one comes from that connector with the alternator wire. The alternator on that diagram shows a brown with yellow stripe wire going to the charge light, powered by a green wire from the voltage stabilizer. That gets power from the ignition switch through the fuse fox to the green wires. On my car (and the S4 wiring diagram) it shows a white wire from the ignition switch to the ignition tell tale, and a brown with yellow stripe wire from the regulator (a generator pictured in the original wiring diagram). But I don't see a wire on either diagram that comes from the ignition switch to "activate" the alternator.

Here's what I've done:

1. Recharged the battery overnight, was fine in the morning, started and ran again.
2. Tested alternator for charge, had 12.8 v at battery with engine off, 12.5 v at battery with engine running and revved up to 2k or 3k rpm. Thinking bad alternator.
3. Took alternator to a shop today to have it tested. He said it's putting out about 30 amps at 14.5 volts, said with the fan I might want to get one with more current. Said make sure the small wire at the alternator was getting power with the key turned on.
4. Took 6 year old battery to get tested. Said even though it was fully charged, it wouldn't hold a load, so bought a new one.
5. Installed new battery.
6. Tested the small wire at the back of the alternator. It only lights the test light dimly, and shows only 12 volts.
7. Tested the small wire at the back of the alternator. Bright test light and 12.5v with engine not running. Continuity from that point to the terminal on the starter solenoid.
8. Reinstalled alternator. Hooked everything back up. Started the engine. Only 12.5 v at the battery with the engine running, even at high RPM, so still not charging.

Is the low voltage/weak test light on that small wire at the back of the alternator the problem? It's part of the large plastic plug on the back of the alternator, so not easy to run a separate test wire to it, but is that the next thing to do?

Hoping someone has a similar issue with an alternator modified S4 car that can help me out.

Cheers,
Rick
70 S4 (Federal) 45/0030K

[mark030358]

Hi,
Make sure the lamp in the instrument works i.e. is on when the ignition is on, but car not started,, this is the excitation for the alternator. Make sure those connections are clean and use a voltmeter not a lamp. Also check your earths, especially the main one at the rear in the boot through to the chassis.
Cheers

[pharriso]

Rick, sorry to hear of your issues.

What is this thing in the center of your picture? Does it interrupt the black wire?

[Craven]

Could check the wattage size of the charge lamp in the ? speedo, this provides the excitation current of the alternator.

[vxah]

Rick, a 17 acr is so simple, it only needs two wires and ground through the body.
The telltale must not be fed from the voltage stabiliser, it needs an ignition on feed and about a 3 watt bulb. You could set up temporary wiring to test things out? Run a new Heavy Brown Wire from the alternator to the starter solenoid (battery side) and the telltale hooked up, it should work!

[oldelanman]

IMG_20200909_143010162.jpg (116.6 KiB) Viewed 1188 times

Is the tape covering a join in your red wire ? You may have a bad connection or high resistance there.

[rgh0]

It also looks like the steering shaft is contacting the alternator when the engine moves under torque reaction judging by the shiny section on the shaft next to the alternator . This will be be doing either the steering or the alternator any good

cheers
Rohan

[hubrick]

Thanks for all the replies.

rgh0 - I hadn't noticed the alt/steering shaft rub, I'll check it

oldelanman - yes, I had noticed that taped section of wire. my car had/has many places like that, i've been trying to check/replace them all in other circuits, time to do it here too

vxah - yes, simple. I don't know if the tell tale is provided power through the voltage stabilizer, just the +2 S130 wiring diagram I used for the DB10 box wiring shows it that way. I thought about running a heavy brown wire directly from the alt to the starter solenoid, but there's that black plastic plug to get around to connect it to the back of the alt. I'll figure a way

Craven - should have checked the wattage while I had the dash and instruments out for a month, but I'll pull it out and see if it's too much. Seems to be normal - red with the key on, dimly flashing at idle, and out at higher rpm.

pharriso - I was hoping that someone could tell me what that thing is in the center of the picture. The big wire from the alternator goes into it and two big wires come out of it, one to the starter solenoid, and presumably one to the control box. There is good continuity from the back of the alternator to the starter solenoid, so whatever is in there is making a good connection. Guess it's time to pull it out and take a look.

mark030358 - yes I checked it with a volt meter after getting the dim test light. It was 12 volts, about 0.5 volts less than the battery. Yes, the light works as it's supposed to, just not getting 14.5 volts to charge. 12.5 volts at the starter solenoid with the engine revved up to 2k rpm. Seems like the light would be on indicating I'm not getting a charge, can anybody explain how that circuit works - why is the light off when charging and usually on when not charging? Mine is not on even though it doesn't look like it's charging. You mean the ground for the battery wire in the boot?

I'll dive back into it on Saturday. Thanks for the suggestions.

[Craven]

Indicator lamp, one side is connected to the battery, the other side is effectively connected via the IND terminal to the output of the alternator. When no voltage is being generated by the alternator, current flows from the battery through IND terminal, through the internal voltage regulator causing the lamp it to light. As the output voltage from alternator rises the potential difference across the indicator lamp reduces, the lamp dims to the point where the voltage from the alternator output exceeds the battery voltage, thus indicating voltages are such that current will flow from the alternator output terminal to the battery.

[nmauduit]

just to be sure, did you check the battery ground cable to the chassis in the trunk ?

[wotsisname]

I had issues getting my alternator to work. The problem in the end was that the ign warning lamp was earthed at the speedo case. I will have to look at my wiring diagram (+2, early) to remind myself why this was important.

[hubrick]

Hello All,
Well, "diving back into it Saturday" turned in to 10 days. Life got in the way, with a hurricane, pulling the engine/transmission in one of my other little British cars to change the ring gear, clutch, rebuild the trans and the carbs, and we made it to our first attended car show this year in Natchez this past Saturday - wow, it sure felt great to be back out with the crowd again (masks, social distancing).

So here's what I've turned up. The funny looking thing in the earlier picture is a capacitor, I've attached another picture of it. Apparently to suppress noise for the radio. Took the connections apart, cleaned them, back together, don't think that was the problem. Same voltage on both sides of it with the car off and running.

Potential problem with the "taped" red "exciter" wire to the alternator. Removed tape, soldered connection. Ran a jumper wire from the fuse to the alternator. That voltage is 11.7 too, when the battery is 12.5. Didn't make any difference with the alternator output.

Haven't checked the wattage of the ignition light in the tach yet. Don't need to now that I've bypassed that wire to the alternator and still no charging.

Took apart, cleaned, wire wheeled/brushed all the connections for the battery ground at the earth bobbin in the boot. Still no difference with the alternator charging.

Talked to the guy at the shop that tested the alternator good a couple weeks ago to see if there was anything else I could do to make it work in the car. He said run a jumper wire from a brown wire at the control box to the alternator. That's 12.5 volts, red light in the tach is on all the time, but hey, it's just temporary. Didn't make any difference with the alternator output.

So I'm out of options again. I'll call the guy at the shop in the morning and see if he can test the output while it's in the car. If not, I'll take it out again and bring it back to him to check it again, maybe see how he's hooking it up on the bench.

Anything else I'm missing?

Thanks all,
Rick
70 Elan S4 (Federal spec) 45/0030K

[hubrick]

Hello All,
Figured I'd give you a final wrap up of my alternator woes. Turns out the alternator was bad. With no other alternative, I took it back to the same shop as a couple of weeks ago, and this time he said it was intermittent, but mostly not putting out anything, so it was bad. Sure wish he would have said that the first time.

After checking that my electric fan draws less than 10 amps, I decided to just fix it. Turns out it was worn brushes and a broken wire, he had it finished in about an hour for $40. On retest, he said it was putting out 45 amps, so it must be an 18ACR. 45 amps will be plenty.

Took it home, reinstalled it (again), and this time it's charging the battery. Finally.

Maybe now I can get out there and start putting some miles on my Elan.

Thanks for all your help.

Cheers,
Rick
70 S4 (Federal) 45/0030K

[Hawksfield]

Rick
Well done, you got there despite poor support from the proff shop expert.
One good thing you learned your way around alternator circuit.