Club 80-90 Forums

Hi All!

I am hunting for a gremlin that blew my alternators voltage regulator which blew my battery.

First I had 17V charge that boiled my battery, then I put in new regulator and new battery and 50km later I had 19V charge. Fortunately this time I had the multimeter plugged in so stopped immediately and saved the battery. Managed to get home without headlights and I lost 0.2V charge on the batery after 3 hours.

The alternator is now off to the rebuilders, but I think that the problem is still in the system.

I have around 1V voltage drop when switching the headlights on and another 1V drop when switching on the front heater fan. Are these normal or high measurements? I think they are high.
The headlights are relayed and I had Osram nightbreakers.

Can they caused the fail of the alternator? Any other thoughts?

Thanks!

can't really comment on the fault, but i can on the voltage drop..
Measured from the fuse board via scanguage.
no fan, no lights = 14.4v
fan speed 1 = 14.1
fan speed 2 = 13.9
fan speed 3 = 13.8
fan speed 1, lights on = 13.7
Diesel van, original wire running from rear to fuse board. At the battery/alternator end the voltage stays at 14.4 whatever happens (120amp)
headlights running off relays, but only from the rear of fuse board not dedicated wire from battery.

have you tried a different multimeter incase yours is out of calibration?

Thanks Lloydy!

I have only one multimeter, a small Düwi 07974, but will buy a bigger one next week to measure amperage higher than 200mA.

I before the regulator blew, I had
14,4 without anything,
13,4 with headlights,
12,4 with headlights and fan at speed 3

These numbers were read at the factory radio connector in the front. And I had 14,6 at the battery.

any old multimeter will do, just as a comparison to what yours reads

1V drop is not unusual with high current like headlights and heater motors.

V=IR or R = V/I
110W of headlights is 9.2A at 12V
12/9.2 is 1.3 ohms
not unusual, better contacts and thicker wires will help

lloydy wrote:any old multimeter will do, just as a comparison to what yours reads

I can only borrow my brothers one, but I wanted to buy a bigger one anyway. Beside that I have to buy bulbs too as they did not survive the 19V (or the relay, have tho check it also) so they are next weeks tasks as everything is closed due to new years day.

itchyfeet wrote:1V drop is not unusual with high current like headlights and heater motors.

V=IR or R = V/I
110W of headlights is 9.2A at 12V
12/9.2 is 1.3 ohms
not unusual, better contacts and thicker wires will help

Thanks.
I think I must clean the contacts and earthing points before the next measurements.

ZsZ wrote:I am hunting for a gremlin that blew my alternators voltage regulator which blew my battery.

I can't think of anything on the vans electrics that would cause this. Not been doing any arc type welding on it have you? (that can damage alternators etc).

As long as the rebuilders do their job properly on the alternator, I reckon that will sort it. (personally I would have gone for another alternator, just to be sure).

And +1 on the voltage drop = connections mostly, then degregated wiring. CovKid has written some very good info on this (and what to do about it) in the wiki.

ghost123uk wrote:Not been doing any arc type welding on it have you? (that can damage alternators etc).

Not welded it since the summer of 2013 and then I had a 65A alternator instead of this 90A.

Can too big batteries damage the alternator? I had an earlier 80Ah Alpha low height for main and a 80Ah Banner energy bull for leisure.

E D I T: Just read this: https://club8090.co.uk/wiki/VW ... ry_to_dash" onclick="window.open(this.href);return false;
I think I need to make a list for the autoelectrics store.

another question: is a battery separator instead the simple combining relay can remove some load from the alternator?

like this http://www.ivt-hirschau.de/product_info ... ucts_id=46" onclick="window.open(this.href);return false;

ZsZ wrote:Can too big batteries damage the alternator?

No

ZsZ wrote:another question: is a battery separator instead the simple combining relay can remove some load from the alternator?

like this http://www.ivt-hirschau.de/product_info ... ucts_id=46" onclick="window.open(this.href);return false;

No, that device is not required and would have some disadvantages regarding charging your leisure battery. A simple split charge relay is fine. You have the luxury of a 90A alternator and that will have no problem charging the two batteries you have (assuming it is working correctly). Remember, most of us have only 65A alternators on two batteries and there are no problems there either.

OK! Thx ghost123uk! Then I will keep measuring voltage drops, and get the leisure battery tested by a shop.

I wouldn't get it tested by a shop. In my experience they are quite likely to get it wrong one way or the other. They will say it's faulty to sell you a new one or they might just be not competent to test it correctly. Plus, a leisure battery must NOT be tested using the usual high current discharge test, it will damage it.

Best gett your meter out and measure the voltage on the battery before putting it on a normal charger, and again after an overnight charge (but left for an hour off the charger before measuring) and again, leave it not connected to anything and measure it 24 hours later. Post those three results here "we", can likely tell you more about it's condition.

I still reckon, as I said further up, if you can get another alternator, and they are quite common fitments to many VAG cars of the era, then you will 99% be sure of curing the problems you had. (you might have to swap the pulley off yours to another alternator = no problem there usually)

ghost123uk wrote: Best gett your meter out and measure the voltage on the battery before putting it on a normal charger, and again after an overnight charge (but left for an hour off the charger before measuring) and again, leave it not connected to anything and measure it 24 hours later. Post those three results here "we", can likely tell you more about it's condition.

I have only a Lidl and an Aldi "smart" charger. Maybe I should get a 6 or 12A "dumb" charger anyway. Next week I will post the measurements.