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Tue Jul 01, 2014 2:30 pm

Hello
I was driving on the motorway when the Gen light came full on. The engine was roasting.
There's obviously a problem but what is it?
My fan belt is new and is tight, has the correct deflection. I can't feel any rubbish in the fan front.
When I look at the engine, the fan belt is turning.

If it was just electrical would this cause my engine to be roasting hot, I don't think so. The gen light was on when the fan belt was turning.

Any ideas please.

Tue Jul 01, 2014 3:49 pm

Top up or down?

Tue Jul 01, 2014 4:54 pm

Remove the belt. See if the generator spins freely. From your description either something is binding or the fan is jammed up with something.

Tue Jul 01, 2014 8:21 pm

Is it always on now? If it stays on, your generator isn't charging anymore.

As for the overheating? Was it overheating before, or just recently out of nowhere? Maybe the distributor moved? A bag got sucked in?

Tue Jul 01, 2014 9:49 pm

Hello, thanks for the replies.
Just re checked the belt tension, this now seems to deflect nearly an inch and the brand new belt has a shine to it, therefore I'm guessing the belt needs tightening. I have turned the generator by hand and can feel the fan / generator catching on the tinware of the inner fan shroud,is this an easy fix and what would be causing it?

Ps this is on a 1978 convertible beetle 1600cc

Thanks

Wed Jul 02, 2014 7:34 am

If I owned it I would remove the generator/cooling fan assembly and see if something had come loose or it is moissing something like a spacer. There is not much play around the spinning cooling fan and the shroud. A bit of play could make it rub
I found this diagram to help you do your inspection.
I hope you find your problem

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Wed Jul 02, 2014 7:40 am

Almost forgot...........
This is pretty easy to remove and fix if you find something wrong. About the most difficult thing is keeping the alternator shaft stationery while loosening the the 36mm nut. Its #26 "Special Nut" (Like ME!!) that holds the fan on.

Wed Jul 02, 2014 7:41 am

Yup. Sounds like something is caught in the fan. It would explain your shiny belt and other symptoms. I'd take it all apart as mentioned above. Depending on what time of screws/bolts used, you might be able to take the fan out without removing the shroud. I use hex head bolts on the bottom 2 holes that mount the backing plate to the fan shroud so that I can remove them with a wrench. You would have to remove the nut on the back of the fan to do it this way as the generator would come off without the fan, then fish the fan out.

Wed Jul 02, 2014 9:17 am

Great replies and a great diagram.

I couldn't feel any crud when I fished my hand around the front of the fan.

One thing that's bugging me prior to my inspection (next week) from immediate start now, the gen light just stays on. When I move the pulley by hand I can feel the fan turning. The belt has definitely loosened and is deflecting about a quarter of an inch ,but I can see the belt moving when the engine is turning over so I'm confused as to why the light is staying on?
Is it possible for the belt to be turning but not turning the generator?

My understanding is, if the belts turning as is the fan when I'm looking at it, why is it getting roasting hot and the gen light stays on, surely if it's turning it's also charging and cooling the engine with the fan.
(Don't worry I will carry out the inspection next week, just confused why the symptoms are there if it appears to be turning).

Wed Jul 02, 2014 9:21 am

There could be some obstruction or the generator ciould be seizing which would make the generator spin but slower than it should be and the belt would be slipping on the generator pulley.

Wed Jul 02, 2014 10:11 am

14platoon wrote: Great replies and a great diagram.

I couldn't feel any crud when I fished my hand around the front of the fan.

One thing that's bugging me prior to my inspection (next week) from immediate start now, the gen light just stays on. When I move the pulley by hand I can feel the fan turning. The belt has definitely loosened and is deflecting about a quarter of an inch ,but I can see the belt moving when the engine is turning over so I'm confused as to why the light is staying on?
Is it possible for the belt to be turning but not turning the generator?

My understanding is, if the belts turning as is the fan when I'm looking at it, why is it getting roasting hot and the gen light stays on, surely if it's turning it's also charging and cooling the engine with the fan.
(Don't worry I will carry out the inspection next week, just confused why the symptoms are there if it appears to be turning).
Two thoughts;
1. The generator is not turning fast enough because of some sort of interference making the light come on at start and stay on. The friction caused by something rubbing like the belt or fan could be causing all the excess heat you mentioned. Also if the fan is not operating as it should that will definitely contribute to cooling issues.
2. The generator has been damaged due to excess heat. I would take it somewhere and have it tested before you re-assemble everything.

Thu Jul 03, 2014 3:59 am

Does the generator spin by hand with the belt removed?

Thu Jul 03, 2014 9:20 am

Not sure I'll try when I'm back with the car. What will that show?
Thanks

Thu Jul 03, 2014 9:34 am

There are shear keys on both shaft ends, one for the pulley and one for the fan. If one of them broke you would be able to tell by rotating it through by hand.

Thu Jul 03, 2014 11:11 am

So if it spins by hand without the belt on something's broken?

Thanks

Thu Jul 03, 2014 11:43 am

14platoon wrote: So if it spins by hand without the belt on something's broken?

Thanks
Without confusing the issue, when you spin the generator pulley by hand the whole assembly, pulley, generator internals and the fan should rotate as one. I believe you had already confirmed that the everything rotates but something is rubbing. I think the other poster was trying to confirm that the pulley and/or the fan were tight and not spinning loosely on the shaft.

Thu Jul 03, 2014 12:32 pm

Ah got you, thanks for the clarification. Kind of looking forward to the job but think it may be one of those pigs that ends up being difficult!
I'm kind of hoping it's just a loose fan belt, but I'm going to give it a once over anyway.
Thanks for all the input so far, very helpful.

Thu Jul 03, 2014 12:34 pm

Just another point. If the battery has run down as a result of say a fan belt slipping, would this cause the generator light to stay on as the battery has a weak charge in it?

Thu Jul 03, 2014 1:38 pm

One thing I remember from my list of stupid VW achievements is that leaving the alternator strap off or loose on a T1 engine causes the alternator belt to slip and the fan to spin slower and the ignition warning light to start to glow at higher RPM.

It is worth checking that the alternator is securely strapped to the stand. Or all your setting up of fanbelt tension goes out of the window as the fan housing rocks around.

Thu Jul 03, 2014 2:16 pm

the generator light only detects failure of the generator to charge the battery, it does not indicate over heat (the oil pressure light kind of serves that purpose as over heated oil can loose enough pressure to cause the pressure light to illuminate.
the generator is associated with the cooling system however, as the belt that turns the fan also turn the generator.

If either light illuminates while on the road driving you must stop immediately and find the problem, failure to pull over and shut down right away can lead to bad bad engine damage.

If the generator light is on when the motor is at other than idle, either the generator is not running fast enough (slipping belt) or there is an electrical fault.
If the cause of the illuminated light is a slipping belt, then the generator AND the fan will not be spinning fast enough, and the slow fan will cause over heat of motor.

The slipping belt can be caused by a loose or oily belt, or there is something dragging on the fan or generator that is causing the other wise correctly tensioned and oil free belt to slip. If the fan for instance is hitting something in the fan house, if may cause enough drag on the fan and generator that the belt will slip, the fan and generator will spin too slow and the generator light will illuminate.