Alternator not charging - relay tray issue ??

[Rweiss6]

Disconnected wire from
Post- measure about 12.0 volts
Put multimeter to post and ground- measured zero
Grounded loose wire , light went on !

Light was not working today before I disconnected ( sometimes it did). Used some sandpaper on post before reconnecting, still no light.

Ready for next step…..

[18Fiatsandcounting]

An '81 spider would have an internal voltage regulator (internal in the alternator) assuming it has the correct alternator, but the charge light on the tachometer must be working for the alternator to work. Also, this particular bulb cannot be an LED; it must be incandescent to allow enough current to flow to energize the alternator so it can do its thing.

If the engine runs, what voltage do you see on the alternator output post when running? If you see only battery voltage (12 to 12.6 volts), then the alternator isn't charging. It should be putting out around 13 volts when idling and up to around 14.4 volts when you rev the engine. A voltage much higher than that indicates that the regulator isn't, well, regulating.

Based on what you've described, I doubt that it's an issue with a relay in the tray under the passenger side dash. Or anywhere else.

-Bryan

[Rweiss6]

Just dbl checked - turn key to run - no battery light
Disconnected wire from alternator, grounded it- lights turns on nice and bright

I had checked voltage at alternator week or so ago, it was 13.3 approx , and increased a bit when revving engine.
I also did that the other day , when I knew light was out,
Checked voltage and it was 12.2 approx

What does it mean when light goes on w grounding ?
Is the problem w light circuit or w the alternator, or maybe can’t tell yet ??
New to me. Very interested to get this figured out , do whats needed , and get back on the road !!
Much appreciated !!!!

[spider2081]

What does it mean when light goes on w grounding ?

his is a good indication the light circuit is working. The alternator needs the voltage on the light wire to excite the alternator before it starts spinning.

Is the problem w light circuit or w the alternator, or maybe can’t tell yet ??
I think the problem is with the alternator. There is a good chance its with voltage regulator/brush assembly. This assembly is held to the back of the alternator with 2 screws. be sure to disconnect the car battery before doing anything to the alternator. The cars battery is connected to the alternators output post.

New to me. Very interested to get this figured out , do whats needed , and get back on the road !!
You could remove the alternator and have it tested at one of the big box parts stores. I feel that is a better test than having it tested in the car.

[Rweiss6]

I just read interesting posts from 2016 about VR and alternator problem. Mine is a 65 amp Bosch, prob orig to car, it shows 82,000 miles , spent many years in Canada ( summer use ??) and 15 years in storage , so maybe real mileage.
Anyway , that post ( many were yours ) suggested getting new VR from Auto Ricambi or Vick ( recommendations?) and replacing it.
Should I try that first , so don’t have to remove and replace alt ? At least not yet
Also, does it make sense for light to not work at all, if prob is VR ? Or does it indicate bigger alt failure ?
Also, other day it worked fine for little while, then not, I had thought maybe loose wire somewhere ( dropping that theory) but maybe fully warmed up made some difference?

If I start car, test voltage at alt again, and it’s 12.2 , do I still need to take to local advance or auto zone or O’reileys ? Thank you

[Rweiss6]

Meant to add - light does not go on when engine running and alt not charging ( batt tests at 12.2 apprx)
Also, as noted , light not on when key in run position, engine off
If alt is failing, shouldn’t light go on when running ??
That’s when it’s needed of course.

[18Fiatsandcounting]

If alt is failing, shouldn’t light go on when running ??

That's what should happen, but your charging light is not coming on when you turn on the ignition but before starting the engine. It appears the bulb circuit is working, but if the light doesn't ever come on (running or not), then something is wrong internally with the alternator or voltage regulator.

With every wire connected as it should be, what voltage do you see at the alternator output post with the engine running? At one point you mentioned you saw 13.3 volts at idle and more when revved, which is normal, but then you mentioned seeing only about 12 volts more recently, which isn't normal.

Given that these alternators are available in rebuilt form at most auto parts stores (or they can quickly get one) for around $100, it may be worth swapping out the alternator. Having it rebuilt or spending more time diagnosing would likely cost you more. That being said, if an auto parts store near you will check the alternator for free (or a small amount of $$$), I'd try that first.

The one thing that I still don't know is if the charge light bulb is LED or a regular incandescent. The alternator won't work if that bulb is an LED, even if the bulb works. Too little current flowing to energize the alternator.

-Bryan

[Rweiss6]

Bulb is incandescent I’m sure. I’ve never changed it ,

Just started car, voltage at alt is 13.4 , at battery 13.2. Didn’t rev engine
Batt Light was on - for 2 seconds- then went off before started car. It flickered for a moment - that’s new- then went off. I measured alt and batt after that , so alt was still working , but maybe failing ??? Other day I had 10-15 min ride w alt working, but after another 10
Mins , checked again and was not.

Could it be slowly dying ? The VR or alt , both ??

Also , I heard a newer squeal type sound , from belt area, certainly could be from alt , it lasted minute or so and went away.

If next step is new alternator ( willing to test more if makes sense ) , which one to buy ? And which not to buy ?
Happy w 65 amp I think I love the car but don’t necc need orig Bosch alt if other types easier to get and ( maybe easier to install )are avail, Appreciate advice on next steps

[spider2081]

The chance of the voltage regulator/brush assembly is about 60%
Your symptom could be worn brushes and they are part of the voltage regulator assembly.
I don't think one can tell much more with out removing the voltage regulator from the back of the alternator and giving it a good visual inspection. Keep in mind if the brushes are worn the armature slip rings are probably worn also. So replacing the voltage regulator is not the same as installing a repaired alternator.
Personally I like the Bosch 65 Amp alternator. They are very well built and very reliable. Being old for an alternator is far from being old for a huuman. Just ask me.

[Rweiss6]

Thank you all, funny thing- both lights on this morn, started car and light stayed on , actually working as it should. Time for new alternator , no more testing
I have ordered parts mostly from Auto Ricambi, (including brakes and high torque starter year and half ago, it’s been great improvement ) , so unless someone advises something else, I’ll order 65 amp from them, and new belt too , mine is couple years old but prob good idea. Any advice or heads up appreciated
I’ll disconnect battery first, and have at it !! First timer, should be interesting

[Rweiss6]

An update may be helpful to others, esp rank amateurs like me
Bought 65 amp alternator from Auto Ricambi, installed it myself - you tube video helped.
Measured voltage at battery and alternator, was 14.3 at both. Old one never was above approx 13.3 when it was working at all. Batt light functions as it should

This forum was very helpful in determining the problem
And advising next step, now and many other times too

If anyone can use the original (I believe) Bosch 65 amp that came w car when I bought it 3 1/2 years ago, I packed it up well, and will send if you pay postage. Hate for it to sit here, or get thrown away

Car did stall and not restart when warmed up , wondering if new higher voltage affected the Ignition control module ? Did start after 15 mins and got me home. Wonder if any connection? Thanks again

[spider2081]

If anyone can use the original (I believe) Bosch 65 amp that came w car when I bought it 3 1/2 years ago, I packed it up well, and will send if you pay postage

I'm interested in the old alternator if shipping is not too expensive. Where do you live??

[Rweiss6]

I’ll PM you. I’ll figure out cheapest way , happy to get it into good hands, maybe easy rebuild ( for you !!) someone can use it again.

[spider2081]

I replied to your PM with a PM