Alternator/Generator Pedestal

The saga begins ... Dave wrote to Rob - Just about the first thing we replaced in this car was the alternator pedestal. It was cracked all the way around near the bottom, we discovered the problem when oil ran out all over the place when we put oil in the car. Could this be a result of stress and strain caused by the fact that this engine ( a '71) is equipped with an alternator rather than the generator that it's supposed to have?

Dave replaced the alternator pedestal with another cheap one purchased from one of the VW parts catalogs. This pedestal, like the first one, was made of pressed powdered metal -- made in China.

Two years later Dave had the same problem with the broken alternator pedestal! He reported - I took the fan belt off and started jiggling things and found that the whole assembly was loose -- because the alternator pedestal is broken in two right at the base, just like before! What concerns me most is the underlying cause. There's got to be something basically wrong that is putting so much stress on the alternator pedestal.

Rob responded - That IS strange. Here's a thought -- there are several different fan backing plate shapes (the piece which bolts the fan to the shroud). I don't know all the details, but even though they look similar, the non-doghouse one is different to the doghouse one (because the fan is 5 mm wider) and the 38-amp generator (Buses/Kombis) plate is different again (that generator is longer). I wonder if the Beetle generator and Beetle alternator versions are a little different, and whoever overhauled your engine used the wrong one -- putting stress on the pedestal. I can't see any other place of conflict which would stress the pedestal.

A few days later Dave found that all four of the fan cover bolts were totally MISSING! Whether cause or effect, there's sure something wrong.

Rob responded - Now THAT would certainly cause some stress on the alternator pedestal. It has the spinning weight of the fan on one end, and the downward force of the tightened fan belt on the other. No wonder it cracked. But I can't see you leaving four bolts out altogether, but then if they were there, where are they now??? They have nowhere to go except inside the engine compartment. Didn't have four spare bolts last time you dropped the engine did you?

Dave wrote - I haven't had time to have a thorough look -- they may be there inside the engine compartment. You know, both bolts that hold the oil cooler tin in place also vibrated loose, and this afternoon I also discovered the cause of the recent intermittent miss -- the nut on the positive side of the coil had vibrated loose, and the wire was just loosely connected!

Dave wrote to "Speedy Jim" - I have a very perplexing problem with my '73 SB ... For the second time in our experience with this car (2-1/2 years), the alternator pedestal has broken in two -- a circumferential crack all around the base of the pedestal. This was the first of many problems that we have repaired in this car since we purchased it in June 1997; now it has happened again.

By way of background -- this car (chassis no. 133-3001-550) was built late in the 1973 model year. The engine in the car was replaced by a PO with a 1971 model (#AE320891) that is equipped with an alternator with an exterior voltage regulator (under the rear seat). VW changed from a generator to an alternator in mid-1973, so originally this engine had a generator rather than an alternator. I don't know whether this change has somehow altered the system so as to put excessive stress on the alternator pedestal, but it's a consideration.

Not only is the alternator pedestal broken in two, but ALL FOUR of the fan cover bolts have worked themselves loose and are missing! The bolts associated with the oil cooler tin have also worked themselves loose. I don't know whether this is cause or effect.

I am in the process of raising the fan shroud and pulling the alternator/fan assembly out of the car. I have a new alternator with an internal voltage regulator on order from Aircooled.Net, but I am very anxious for your advice before putting the system back together to make sure that I have addressed the root cause of this problem so that it doesn't recur. John Connolly has recommended that I replace the fan, but I'd very much like to hear what you have to say about this situation before I proceed.

"Speedy Jim" responded - I have never heard of a failure like this...never. Given all the other mysterious things happening (loose bolts), I very much agree that the fan should be replaced. There are two fans, one for non dog-house and one for dog-house coolers. Are you also aware that the alternator belt is different from the generator belt?

Rob wrote - It's a weird problem, and I just can't think of why there would be stress associated with the fan to alternator, and alternator to pedestal fixings which would a) loosen the fan mount bolts and b) crack the pedestal. Where the bolts went is a big puzzle too -- maybe they are lodged behind the induction manifold just below the fan plate, or maybe they are in the well under the engine pulley. As I said previously, the only thing which comes to mind is perhaps an incorrect fan mounting plate used on the alternator.

Dave wrote a progress report - I AM going to have to raise the fan housing, even though the alternator is totally loose, so that it will clear the intake manifold. Hopefully that will become obvious when I get the alternator/fan assembly removed.

Rob responded - I was wondering if you would. That would be a "given" on the single-port engine (one-piece manifold) but I wasn't sure with the dual port. But I guess the outer ends would be in the way (on the right side particularly).

Dave wrote of continued progress - I went out tonight and took the alternator strap off, screwed in the two top bolts in the fan cover to hold the alternator up (my concerns about the nuts being stripped were unfounded) and removed the broken alternator pedestal. It's now sitting on my workbench in two pieces. I'm not understanding this. One would think that the fan cover bolts were inadvertently left off, causing vibration and stress ...

Dave wrote to "Speedy Jim" - I'm pretty sure the problem lies with me. I dug out a picture that I took of the engine after I had it all reassembled and cleaned up, sitting on the patio before reinstalling it. I scanned the picture at 200% and took a close look at the two top bolts in the fan cover. The blow-up is a bit fuzzy, but I'm pretty sure the bolts were missing! Apparently I neglected to put them in.

Like Pogo said, "We has found the enemy, and they is us!"

"Speedy Jim" responded - I don't think leaving all four bolts out would make any difference. The cover is only there to keep the air inside and to locate the shroud reference to the fan. I don't think you're going to be able to take the blame for this! :-)

Dave responded - But -- if leaving the bolts out isn't the reason the pedestal broke, what IS? This is the second time this has happened in this car -- there's got to be some underlying problem... I keep coming back to the alternator itself. This engine is 1971; VW didn't put alternators in Bugs until mid-1973, yet this Bug (itself a 1973 model) has an alternator with an external voltage regulator. Is it possible that this mismatch is somehow causing a problem that is putting excessive strain on the alternator pedestal?

"Speedy Jim" wrote - I would be looking for more clues, I guess, such as -

• Does the fan belt exhibit any peculiar vibrations through a range of RPM's? (I assume it's not overly tight.)
• I'd try to rig up some way to spin the alternator at high RPM (without the engine running) to look for unusual vibration.
• After I got the fan out, I'd examine it closely for any signs of damage. (By the way, you will need an impact wrench to get the fan off.)

Rob wrote - I got this reply from my mechanic friend. Couple of good points in it -

• Cracked alternator pedestals are not uncommon.
• Cheap pedestals crack far more readily than the genuine article.
• The 50amp alternator and 30amp generator fan mounting plates are the same, so that should not be a problem for you (there are several different ones -- he mentions the 38amp genny (used in buses).

Dave wrote to "Speedy Jim," John Connolly and Rob - Of course the alternator pedestal MUST be replaced. I'm told that there are two qualities available -- the el-cheapo made out of pot metal, which breaks easily, or the high-quality original VW part. Given our history (two broken pedestals in as many years), I want to get the good one. The question is, WHERE? All that I've seen are the el-cheapo ones.

• Aircooled.Net - If you need a genuine VW pedestal, I do NOT have them. You will have to get it used somewhere.
• Wolfsburgwest - This part does not appear in our catalog due to the poor quality units currently available. Unfortunately, I do not have a source for an original unit, sorry. Try locating a used piece, that's your best bet. Russ' Recycling in Duarte, California is an all-VW wrecking yard, they may have one.
• Russ' Recycling - They sent Dave an original-equipment alternator pedestal for only $15!

Dave wrote - We have a dearth of wrecking yards around here that have VW stuff, so this is a very valuable find! I have ordered a used original alternator pedestal from Russ' Recycling. Once I have this "new" pedestal installed, then the reassembly will begin -- a new alternator and a new CDI unit, with all associated parts (fan, etc.) cleaned and painted -- its gonna be gorgeous!

Dave stripped the new alternator pedestal down to the bare aluminum, and it shines like a new dollar!

The original-equipment alternator pedestal from Russ' Recycling has held up for more than five years now. Dave strongly recommends that you do NOT buy the cheap pot-metal pedestals -- they just do not hold up. Get yourself one with the "VW" stamp clearly visible!