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Glowing alternator light tonight!
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Tim Donahoe
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PostPosted: Sat Aug 12, 2017 11:39 pm    Post subject: Glowing alternator light tonight! Reply with quote

I went to a Show and shine today and left after dark. It's been so long since I drove the bug in the dark that I had trouble remembering where the light switch was. Anyway, I drove the eleven miles back home, and when I pulled into the garage and the engine was idling, I noticed the alternator light was faintly glowing. Rpms were fine. At this point I revved the engine and the light went out, but at idle, it faintly came back on.

Twenty minutes later, I restarted the car and the light faintly glowed, so I turned on the lights and it glowed brighter. Then I took the car for a spin. Sometimes the light grew brighter, sometimes not--even when I was revving it. Then I turned off the lights, thinking the extra pull was merely because the lights were on, but I still got the intermittent glowing on the alternator warning light.

So, before starting the car, I'll first test with a multitester to see if I have around 12.6 at the battery, then test again to see if I have 13.8 to 14 after starting the engine, and eventually at at two thousand Rpms.

My question is this: Which grounds do I check and clean, if any, aside from the usual suspects: the transmission ground and battery ground connections?

Tim
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Chochobeef
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PostPosted: Sun Aug 13, 2017 5:28 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

Check the alternator ground wire as well. You should have atleast a 12awg brown wire coming off the body of the alt.

You could have a dirty connection up front at the bulb so check/clean those grounds as well.

Look forward to your results (and pictures)
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PostPosted: Sun Aug 13, 2017 6:02 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

Do you have an internallly regulated or externally regulated alternator? Just a big and small wire would be internally regulated. If externally regulated, I would also check the regualtor connections and would swap the regulator if that hasnt helped. Also look for any potentially funky splices.
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PostPosted: Sun Aug 13, 2017 9:39 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

mine has always done that, 14 years and no issues. I just went to lower wattage led headlights and I dont see any diferance in that issue but I do see a lot better at night now like 8x as good vs the old halogens&hellas. could it be you just never noticed it? might want to check the H2o in the battery.
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PostPosted: Sun Aug 13, 2017 11:09 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

I have a 73 and mine was doing the same thing. what I did was remove and clean connections at alternator and regulator and battery. Nighttime driving now there is no glow with lights on and even wipers.
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Tim Donahoe
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PostPosted: Sun Aug 13, 2017 11:28 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

Internally-regulated Bosch alternator.

Tested just now:

Battery at rest: 12.62. I tested earlier after the car was sitting all night and got 12.13. The car sat for about two hours and got the higher 12.62.

After starting car and at idle: 13.35

With motor running and lights on: 13.13

Lights off at high Rpms: 13.35 again.

Light was on as I turned the key, but went off upon starting and running. Even with the lights on this time.

I'll clean connections and big grounds first and recheck.

Tim
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PostPosted: Sun Aug 13, 2017 5:30 pm    Post subject: Re: Glowing alternator light tonight! Reply with quote

Hi. One very simple method to diagnose whether you have an internal alt issue or its outside wiring is this method.
Disconnect the term 61 wire from the alternator and replace this with a known good bulb and wire set-up. You can utilize another VW bulb holder/lamp and wire it up from the coil term 15 thru the lamp and to the alternator.
If you get the same results you probably have an alternator issue. If the you get a different result you probably have a wiring issue.

VW never ran a dedicated ground wire from the alt housing to ???

If you're ambitious you can perform a voltage drop test on the positive circuit from the alt B+ to the battery positive post and a voltage drop test on the negative circuit from the alt housing to the battery negative post and see if anything shows up more than 0.5v drop.

Hope this helps, Bill.
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PostPosted: Sun Aug 13, 2017 6:22 pm    Post subject: Re: Glowing alternator light tonight! Reply with quote

Tim, be aware that the alternator light comes on when the key is in the run position and the charging system has no output, the light will only glow based on voltage differences at the bulb itself. If for example when running at a rpm that allows the charging system to output 14 volts coming back from the 61 field wire to the back of the dash bulb and the voltage at the other side of the build terminal that come from the battery circuit via the key switch is less than 14 volts (due to voltage drops in old wiring) then the bulb can glow due to back feed. If you have more than 0.2 volts when one lead of your voltmeter is places on the battery positive eye and the other lead is places on the bulb terminal fed by the key switch when the system is reved up, you have a voltage drop that needs correcting. Working one lead voltmeter lead to each connection leading to the battery will show you where the drops are occurring. David
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Tim Donahoe
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PostPosted: Sun Aug 13, 2017 7:13 pm    Post subject: Re: Glowing alternator light tonight! Reply with quote

Thanks for all the replies and teachings, guys. At this point, the garage is very hot. It was so hot, I debated for a moment if I should put my hair in a man bun. Reason prevailed, so I let it hang down.

I decided to first make sure my battery was fully charged, so I put it on a charger and it's been going for 2 and 1/2 hours now on the 10 amp charge. The charger's green light has still not come on (indicating a full charge). This seems weird to me, as if the battery wasn't fully charged, despite the fact that I had a 12.62 after testing this morning. Although, before the first test, I had a resting-over-night battery charge of 12.13.

First thing tomorrow morning, I'm going to retest with a fully charged battery to see if my numbers come up. I'll also clean all the terminals.

Tim
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PostPosted: Sun Aug 13, 2017 7:31 pm    Post subject: Re: Glowing alternator light tonight! Reply with quote

Man bun completely acceptable if it's for safety Wink Laughing
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PostPosted: Sun Aug 13, 2017 8:20 pm    Post subject: Re: Glowing alternator light tonight! Reply with quote

Xevin, I can swing a Q (ponytail), but I guess I'm too conservative for a man-bun.

So, my charger light started blinking green, meaning the battery is fully charged. I tested it immediately after taking it off the charger and got 13.32. I don't know what a fully-charged battery should read, but I'm hoping it's something like below 12.60 in the morning after it rests all night without any drain from the radio memory, or some parasite I'm unaware of. In that case, I can assume the battery is bad.

Wishful thinking, I know; but a bit over a hundred dollars for a good Interstate at Wolfgang Internationl here in town, beats the price of a new internally regulated Bosch alternator, by half.

If, in the morning, the battery is still above 12.60, I'll just have to start testing until I find the issue--after cleaning up the grounds and such, anyway.

Tim
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PostPosted: Mon Aug 14, 2017 4:51 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

Around 12.6 seems about right....Running and charging is usually more like 14 and change. Going for obvious....Fan belt tight?
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PostPosted: Mon Aug 14, 2017 5:57 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

Your charging voltage when the car is running and lights are off doesn't appear to be sufficient. I think minimum you want 13.8 at idle. You could have very worn brushes or they are not making good contact with the commutator. May want to give a look to see how that appears when you remove the brush module and see if the brushes are making full contact.
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PostPosted: Mon Aug 14, 2017 11:12 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

Fan belt is nice and tight.

After charging last night, I checked the battery agin this morning, and it held the charge very well. I hooked it up again, started the car, and retested. I got a 13.80 while running. Still not the 14.00 I was looking for. With light on, I got 13.38. Turning on the two speed fan, also--with lights on--I noticed the lights dim a small amount. The neighbor didn't notice, but I did.

The neighbor came over with a plumbing problem, so I quit work on the car to help him. Now I have to go grocery shopping before it gets too hot outside.

After all the interruptions and chores are taken care of, I'll go back to work on the bug.

The test at the speedometer sounds interesting, but getting to the back of my speedo is a bitch. I have to remove the front dash panels and push the speedo out of the hole (I have the 1974 round screen setup).

Oh, well. If it's not too hot, I'll get back to the car later on.

I still have the transmission ground to clean, as well as the alternator connections. If I don't get a good 14+ then, I'll go through the other tests mentioned above.

Tim
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PostPosted: Mon Aug 14, 2017 11:34 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

13.8v is perfectly acceptable.

Your earlier reading of 12.13v is very poor. The battery is significantly discharged at 12.13v so this may have been the source of your issue.

The question is why was it so discharged? Has the car been sitting for a long time? Do you keep it on a battery tender if you don't use it for a long period?
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PostPosted: Mon Aug 14, 2017 11:54 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

Hi. I believe in a previous thread regarding alternator charging systems, either here or on the Bay Bus section, Telford Dorr or maybe SGKent mentioned the Bosch alt's seemed to be on the low side of spec on charging.

You seem to mention being crunched for time. If so, why not try and fab up a bulb/lamp harness and isolate the entire term 61 circuit from the speedo housing to the alternator terminal? An easy diagnosis that should isolate whether you have an alternator issue or a wiring issue.

Why not consider having a core Bosch or Motorola Alternator rebuilt as your spare? Cores are all over the place for approx. $25 and I just paid a local shop to refurbish one for approx. $85.
Since Bosch's reliability is dropping at an alarming rate I find myself looking for alternatives and they are actually out there.

Hope this helps, Bill.
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PostPosted: Mon Aug 14, 2017 1:10 pm    Post subject: Re: Glowing alternator light tonight! Reply with quote

sj, I only drive the bug a couple times a week. Once is to the grocery (7miles away), the other is to a neared store (2 miles away). Or downtown (6 miles)). I have to start the car when leaving and start it again for the trip home. No issues starting at all. So, I don't drive it much.

The thing is, I figured out that I rarely drive it at night, so I don't turn on the lights. I would also have trouble seeing a dim warning light during the day, but, even dim, I think I'd notice. Perhaps, it simply sits too much (with my new stereo draining a small bit of electricity for memory). That would be great. And my trip back from the show and shine while using the lights was indicative of a battery that needed charging (which I did yesterday).

Well, we'll see. I've had my shower, and I'm off to the grocery. However, while working on the neighbor's sprinklers, I also found a rupture in one of my stations. I'll be tending to that first.

Tim
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PostPosted: Mon Aug 14, 2017 6:34 pm    Post subject: Re: Glowing alternator light tonight! Reply with quote

My 2 cents - you are not driving far enough to restore the juice that you used starting the car. And look at the bottom of your oil filler cap and see if it looks like chocolate milkshake on the underside. If doing these short hops, take one decent drive a week (like over 1/2 hour) to get you charged and cook the water out of the case.
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PostPosted: Mon Aug 14, 2017 10:22 pm    Post subject: Re: Glowing alternator light tonight! Reply with quote

and, I agree with you-halfway. Fortunately, I have a working thermostat--the engine heats up quickly, so my oil cap looks good. I also change the oil often.

Although, I did charge my battery up and still got numbers that I didn't think were up to snuff.

I'll give it a good run and see how it goes. I also still have to clean the transmission ground strap, as well as the alternator leads, but I got stuck today digging up sprinkler pipes.

Tim
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PostPosted: Tue Aug 15, 2017 6:08 am    Post subject: Re: Glowing alternator light tonight! Reply with quote

How old is your battery?

A battery reading of less than 12.25v is suspect. You've lost the surface charge since the last time you drove the car, or the last time you had the engine running. It's possible that you can charge a battery with a reading less than 12.25v if you catch it in time. Anything less then it's hit or miss.

Sitting in Summer heat is the quickest way to kill an automotive battery.

Describe your battery - Is it serviceable, or maintenance free? If it's serviceable and you can remove the caps, check the water level. if it's low, bring it up to top level BEFORE charging. Charge it, then check charge value.

If it's maintenance free, and you read a value of 12.13v, it's a good bet that it's on it's way out. It may still take a charge, but don't forget that you saw it's surface charge at 12.13v.
Here in Florida, automotive maintenance free batteries last maybe 3-4 years on average.

Your original question about the Alt light was already answered, but the battery question remained, in my mind, unanswered. Hope this helps Very Happy
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