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996 alternator voltage regulator

uk996

Spa-Francorchamps
Joined
9 Jan 2018
Messages
282
The idle voltage is around 13.4V. I've always looked out for around 14V. I suspect the VR is on it's way out.

Can someone confirm the OEM part number?
I've found most places say it's F00M144151, F00M144136 and others F00MA45232.

Any one changes theirs? Any tips?
 
Thanks Nick,
looks like the Bosch designation is F00M144136
 
To test ..

Engine at operating temp .. electrical load on so lights on main beam . fog lights , hazard lights , heated seats and radio on ..

If a seperate voltmeter on the battery indicates 13 volts or lower on idle then the alternator or possible wiring has an issue with the alternator being the issue 9.5 times out of ten .

Above 13 and it's fine with a sensible reading of 13.3 - 13.4 .

Don't use the onboard voltmeter .. it's not that accurate .
 
...Operating temperature - very important. Sick regulators don't like heat. my regulator would start at 14 when cold and work its way to 12 (on the dash gauge) as the engine warmed. Took me a while to notice and then Figure it out.
 
I've been relying on the dashboard voltmeter, I'll use another to verify the voltage under load.

I don't have heated seats, so I'll use the cigarette lighter to provide the additional load.
 
I've been relying on the dashboard voltmeter, I'll use another to verify the voltage under load.

I don't have heated seats, so I'll use the cigarette lighter to provide the additional load.

I presume the alternator needs to be removed to change the regulator and can not be done in-situ?

(I've changed regulators on my Hondas where the regulator is separate.)
 
Lights on main beam with fog lights on will be enough .. the main figure i work to is 13 volts and less means its an alternator on its way out .. above that and your ok but 13.4 is what i would like to see.

Basically on idle this is a huge load for an alternator so any issues will show up on this test .

Voltage reg replacement is an alternator out job .

Bear in mind that is not always the issue so you might end up replacing the alternator regardless .
 
I also found the bolts attaching the regulator to the alternator very corroded, so even though I had bought a new regulator ended up replacing the whole alternator (bolts sheared, and I could support it well enough under the pillar drill to tried drilling out by hand, but steel bolt in ali I ended up damaging the housing, so new alternator).

As a word of warning for everyone else, if you see your voltage start to change with revs from 11-14v, and you are 5miles from home, don't persevere, park it up and get recovered. The fluctuations will get bigger and eventually you will blow virtually every bulb that is on, fry the headlight switch and the battery...
 

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