Alternator voltage regulator failure

sunbeamsam

Active Member
So, towards the end of last summer I’m driving along and my aircraft duel ammeter is flickering all over the place as it has done before when some of the connections worked loose. The sun is shining and I’m concentrating hard on trying to diagnose a clutch fault. Then all of a sudden the stereo cuts out, which is annoying. I then smell hot electrics. I stick my fingers behind the ammeter to wiggle things and ouch, I burn my fingers. I then move my mobile phone holder which is covering up the voltmeter to see a worrying 16volts. I’m a mile from home so stop, let things cool down then make a dash back, fire extinguisher in hand.

Multimeter confirms the volts are now completely rpm related and that the voltage regulator must have gone. I order a replacement and order is restored - correct volts, flat ammeter readings and no bubbling batteries.

All this got me thinking.

When I rewired the van I put most things on their own circuit - there are loads of fuses - except for between the alternator and battery. I understand this is the norm for all cars built before the mid80s. More modern cars have some form of fuse link fitted rated at 100 or more amps.

So, the hot wiring was caused by the increased voltage making the batteries take more charge (amps), the acid was starting to fizz as they massively overcharged. Generally though a flattish battery won’t draw more than what - 30 amps?

Question, would I be wise to fit a circuit breaker between the alternator and battery? If so at what rating? Currently (excuse pun) I’m thinking of fitting two 40amp circuit breakers, one on each battery. Is this too much, not enough?
 

Panky

Administrator
Staff member
I think fitting a circuit breaker or fuse is just masking the problem. Sure it will pop if it happens again but what is causing it in the first place? Is there another problem with the alternator that is causing the reg to fail? maybe an intermittent short somewhere. I think I'd be looking at changing the alternator to see if you can get to the root of the problem.
Or you have just been unlucky and have bought from a bad batch of regs.
 

bazzateer

Well-Known Member
I think fitting a circuit breaker or fuse is just masking the problem. Sure it will pop if it happens again but what is causing it in the first place? Is there another problem with the alternator that is causing the reg to fail? maybe an intermittent short somewhere. I think I'd be looking at changing the alternator to see if you can get to the root of the problem.
Or you have just been unlucky and have bought from a bad batch of regs.
Could be wrong but as I read it he had a regulator fail and the replacement is working fine. Not sure there's an ongoing problem other than a single regulator failing?
 

sunbeamsam

Active Member
Yes all is okay now. The voltage regulator is part of the alternator so I bought a complete new alternator (one of the 70amp ones for a mini). I’m just thinking on how to stop this ever happening again.
 

sunbeamsam

Active Member
OCD got the better of me again and my unnecessarily complicated response the the problem that doesn’t exist has been to fit 3 circuit breakers - one for the alternator and one for each battery.

F0C36157-BA3C-44D7-A7EB-23887AA3955E.jpeg

I’ve added little voltmeters with built in high/low alarms. I haven’t set these up yet but they will buzz if the volts go too high like if the voltage regulator fails again.

9D734C40-53A1-4AFC-9025-59A08970AD20.jpeg
Need to charge my main!
 

Panky

Administrator
Staff member
Gives off a strange red glow at night like a spooky atomic clock. It's always around 12 o'clock though
 
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