Voltage Regulator Replacement

After a long drive last weekend I noticed that the battery was very warm to the touch. I checked the current and volatge this evening and discovered that after about 15 minutes of idling, the voltage measured at the battery starts climbing rapidly from 13 volts up to 17+ volts within about 1 minute. I assume this means the internal voltage regulator in my alternator is faulty. Do I have to remove the alternator to replace the regulator? According to my owner's manual, this is a 45-Amp Bosch alternator.

There are 2 different alternators used by VW as OEM. Both are 55A (aftermarket 75 and 120A are available too). Generators are 30-45A. The Bosch or Morotola AL78 with 3 prong plug uses an external regulator that is easily replaced (probably a thin 2" square with M or Motorola written on it - Bosch units may use a different regulator). The AL82 has a replaceable internal regulator. Above number may have an X or N at end of number - X means rebuilt and N means new.

Here's replacement regulator for internal AL82 one:
http://www2.cip1.com/ProductDetails.asp?ProductCode=BOS%2D9%2D190%2D087%2D003%2DUS

Have you looked at Speedie Jim's VW site - http://www.nls.net/mp/volks/htm/elec.htm

A diode could be bad too!

I'm not so sure that charging up to 18V for a low battery indicates a bad unit though (AMP gauges read to 30+/-). Output of alternator and regulator should be able to be tested separately. Does it drop down after 1/2 hour of driving?

Wolfgang - Thanks for the reply. The battery is being overcharged (i.e., over-voltaged) to the point where it becomes hot. The longer the car runs, the hotter it gets. The current level (as opposed to voltage) is reasonable as I switch lights and other accessories on and off. That's the value that you refer to as being displayed on a +/- 30A Amp scale. What is out of spec is the voltage, not the current. I don't believe it should ever exceed the high 14's if the charging system is working properly, and mine is going past 17V.

I can't think of anything other than a bad voltage regulator that would allow the voltage to go out of range (that's the regulator's sole function). My alternator is internally regulated, and I haven't been able to determine if the internal regulator can be changed without removing the whole alternator. If I have to remove the whole alternator, I'm going to replace the whole unit. It's 9 years old, and sooner or later the rest of it will need replacement anyway. If I can simply replace the regulator without the chore of removing the whole alternator assembly, then I'll just change that.

Isn't the regulator under that visible black plastic plate on the alternator?

If you have a sealed (gel cell) no maint. battery, WATCH OUT!!!! Some of these have been known to explode due to gas build up within the cells.....Especialy when radically overcharged.

I would have the battery checked along with the Alt/reg.....Just to be safe....

Oh really? Hmmm... Makes me worry about my Odyssey gel cell.

i had a newer dodge PU and the regulator inside the alternator went bad and it was charging so much it burned up these huge battery cables and melted the battery case.

Leon and Bob - I agree with both of you, an over-voltaged battery can explode and is nothing to mess around with. Not sure how long mine has been on the fritz, but I'm glad I noticed it when I did. The bad thing is that unless you check the voltage or feel the heat, there is nothing to warn you that anything is wrong.

Wolfgang - I think you're correct. I removed the black plastic piece (see pic below), and there is blue wire out the top of it that goes to the dash gauge, which agrees with the regulator depiction on my wiring diagram (if you can see item #22 on the pic below). However, looking at the thing, it doesn't look like it's anything more than a plastic housing with two spring-loaded brush contacts. I suppose there could be a diode embedded somewhere in this housing, but other than that, I can't see any circuitry that would perform a regulating function. I'll try to get another one at NAPA tomorrow.

Battery explosions...I saw one go up as Teamster warehouse worker was jump starting a fork lift off of an 18 wheeler battery.
The entire top of the battery came right up into the poor slob's face like a bomb went off..acid and all. Luckly, he was wearing glasses and there was a garden hose nearby. I had to tackle the guy onto the pavement hold him down tilt his head to the side and run a stream of clean water into his eyes until the First Aid got there....no permanent eye damage. ~Alan

Alan

How tell a generator from an alternator. I have 3 sitting on my bench and trying to decide which one to use/rebuild

Hint - Generators have part numbers stamped in them starting with GR and Alternators AL. An alternator takes a different stand and different mechanicasl fuel pump too.

Alternator:
http://www.kustom1warehouse.net/New_12_volt_alternators_for_VW_p/al82x.htm

Generator:
http://www.kustom1warehouse.net/New_and_rebuilt_12_volt_generators_for_VW_p/generators.htm

With just a glance.
Generators are straight cylindical tube looking units.
Alts. have a larger diameter lump at the pully end.

Felix......I have a Bosch 55A. Alt with internal reg., that was severely damaged when the belt pulley separated at Carlisle 2008....The shaft is eaten up and the face plate behind the pulley was almost cut into......If you think it would help you, It'll cost you postage/shipping.....It was still working well when removed from the car....Less than 10,000 mi. on it.

I found part diagram for a 914 Bosch alternator - and appears regulator in behind what would be the fan on a T1 engine. Sounds like Leon's would fix you right up recycling is great!

Leon - Thanks for your generous offer. I already ordered the above linked regulator from CB. If it doesn't work out, I will take you up on your offer.

Wolfgang - The SOC is a great community!

Alternator has to come out to replace voltage regulator. I removed everuthing that needs to come off to remove the alternator and fan except for the hex bar throttle linkage. How the heck do I get that out? Each end of that bar srews into a threaded hole in each carburetor housing. When I tried unscrewing one side, it bound up against the opposite side. Do I have to loosen each carburetor base in order to get this bar out?

My quick method, loosen one of the carb intakes, lean the carb / manifold out board to release the hex bar ball and socket. ~Alan

Alan - Thanks for the tip. FInally got a few minutes to work on it tonight and sucess!

Hey Felix, just wondering if it was your regulator. I have the same problem now.

Ben - I just got the alternator our of the car Sunday night, and will be changing the regulator and re-installing alternator this weekend, so I'll give an update then. I can't imagine anything other than a faulty voltage regulator that could cause excessively high charging voltage.

Just a thought.....Check the wiring connections for the charging circuit......Loose or corroded junctions can raise hell with charging rates......

Felix,
Any updates? just wondering if it was the regulator.

Ben - I changed the voltage regulator and the problem of excessively high charging voltage/hot battery was solved. I bought the regulator I linked from the CB catalog above. It's the exact same regulator that was in the Bosch alternator to begin with. Hopefully the new unit will last another 8 years like the original. It was easy to change, once I got everything out. I also took the opportunity to replace the fan with a welded, balanced fan as per Larry Jowdy's suggestion, replaced the studs on the alternator stand with bolts and lock washers (makes it possible to slide the alternator stand straight in or out, without having to lift up the shroud), and replaced a downward exiting crankcase ventilation tube with a synthetic hose (also allows stand to slide straight back without lifting up).

I had a battery explode once in a Volvo 142 I had, was on Hwy 400 in Ontario which is a very busy highway, especially after a long weekend in the summer, which is was.

At first I noticed a funny smell, like rotten eggs. Sulfur I would imagine. Kept up for a while and then all of a sudden, Kabloom! Hood went up (to the first catch) and everything went dead. Every electical thing that was on either bit the dust or blew the fuse and battery acid was everywhere. By the way, this was back in the 1970's and the battery was the normal lead/acid battery not a sealed gel unit. So if you smell rotten eggs and you've got no dog in the car to blame it on it might be wise to pull over and check the battery.

I was able to fill the battery up with water and just limp home. Was a faulty voltage regulator.

Brian - That must have been quite some experience! While I didn't notice any peculiar smell, I did notice that the battery was red hot (before replacing the regulator) and I could see small amounts of fluid weeping out of the battery. I'm not sure how long it was in this condition. My battery is hidden under a carpet in the front boot, and there is no voltage gauge on the car. Because the voltage is too high (as opposed to a bad alternator or bad connection that causes the volatge to go low), everything on the car appears to be working fine - lights come on, starts right up, etc. I only noticed the problem because I was moving stuff around in the boot and noticed the carpeting over the battery was extremely hot. When I checked the voltage with a meter, I knew immediately what the problem was. I feel lucky I didn't repeat your experience.

Great news, I'll be ordering mine soon. thanks