Amazon: Voltage regulator help needed!

[Faust]

I've recently replaced my alternator with a 55 amp unit from Brookhouse. I've also replaced the voltage regulator (3 pin type).

The new set up is putting approx 19.2 volts into my battery which is obviously far too much - with the old VR I'm getting a reading of 13.1 volts at the battery at approx 2000 rpm. If I by pass the VR and take a reading at the back of the alt and the negative battery terminal, I get a reading of 14.3 volts which is spot on so the alternator doesn't appear to be faulty.

Simon has sent me 2 new voltage regulators and I'm getting the same problem with both. The connections at the alt. are correct and all earths & connections are nice and clean.

Car is a 1970 133 with the factory alternator set up.

Does anyone have any ideas?

[Ron Kwas]

F;

I'm confused..." If I by pass the VR and take a reading at the back of the alt and the negative battery terminal, I get a reading of 14.3 volts "...that is a fairly normal voltage and to be expected, but please elaborate... How do you bypass Reg on that Alt? If you measure a normal voltage at the Alt output (which you can expect to be the highest voltage point in the system), exactly where and how, and under what circumstances do you measure the 19V?

Without understanding your conditions fully, I'll still try to give some suggestions:

First, and in general, assure all charging system connections are proper, clean and tight...poor connections alone can cause major symptoms such as you are experiencing...

...more specifically, a poor chassis connection to the V Reg (external or internal to Alt, which is not clear to me from your info) can cause the voltage across the poor connection to be added to the reference voltage of the V Reg. The voltage at which the V Reg then tries to keep the system is sky high, as you're experiencing...at that voltage, I expect the Battery to be boiling like a witch's caldron...likely expelling droplets of acid out the vent...so clean and neutralize any expelled droplets carefully and totally, check and top up electrolyte level.

Good Hunting!

[Faust]

When I say by pass; I take a reading from the either of the terminals on the rear of the alternator (to starter motor and/or to battery) with the positive probe of a multimeter and put the neg terminal of the MM on to the neg terminal of the battery and I get 14.3 v with the engine @ 2000 rpm... so the alternator seems ok.

The VR is an external 3 pin tpe (mounted on the inner wing) and I've tried two brand news ones which both give the same symptoms.

The reading of 19 v was taken across the batt with 2000 rpm on the engine and no load on the system.

The battery has been fully charged overnight and is approx 8 months old (Bosch job so hopefully it's OK)

I've checked and double checked all connections and wires for breaks or corrossion and they're all fine. I've cleaned the fusebox and replaced all the fuses (inc. the little 25 amp one).

Scratching my head over this one!!

[david philips]

if me i would check with another multi meter/volt meter , if theres only 14.3 at the back of the alternator then there can not be 19 at the battery?

strange and interesting one this post when you do find out.

[Faust]

Brief update:

I could not get the 55 amp alternator to work with the external VR for love nor money – whatever I tried I got no charge or 19 volts – a couple of blokes on my street (ex-mechanics and pretty good with electrics) also couldn’t figure out the problem, nor could my old man who used to be a sparks in the merchant navy

I threw the towel in and got Simon to swap the alt. he supplied for his 55 amp with built in regulator version (excellent service as always from Brookhouse).

The new alternator puts out a healthy 14.17 volts @ 2000 rpm (measured across the battery terminals) – this drops to 13.75 under load. I’m more than happy with this output!

The only problem now is that my amp light is permanently on! I think it’s shorting somewhere behind the dash and there is not a lot of room behind there so I’ve pulled the bulb (I know this ain’t a perfect solution) for the time being (the system does charge without the bulb fitted).

Next job will be installing some extra gauges: amps, oil pressure and water temp.

Thanks to all who helped on this one.

[Volvo Canadian]

Hi, glad you got that fixed. Interesting and so too bad you couldnt tell us how it happened!

Methinks it is virtually impossible to produce a voltage higher than the output of the alternator; right up there with the "perpetual motion" device I've got in the Estate.

I'm in Canada, but judging by some of the posts I've read on here, it sounds like Simon should be knighted...!

[Faust]

Originally Posted by 122 Canuck

Hi, glad you got that fixed. Interesting and so too bad you couldnt tell us how it happened!

Methinks it is virtually impossible to produce a voltage higher than the output of the alternator; right up there with the "perpetual motion" device I've got in the Estate.

I'm in Canada, but judging by some of the posts I've read on here, it sounds like Simon should be knighted...!

I would've liked to have solved the mystery of the climbing voltage as a) it would've been of use to other forum members, and, b) I really don't like being defeated by a car. Alas, it was not meant to be.

I did shout "we obey the laws of conventional physics in this house!" a few times at the bloody thing (shamelessly ripping of 'The Simpsons').

Simon at Brookhouse is indeed a top bloke... if the Queen drove an old Volvo he would've been Knighted by now.

[amazon69]

Simon is indeed a top bloke..in my box of bits delivered today (including an uprated front anti roll bar for a decent price) what did I find?

That's right...a zesty lemon lolly.

And it tasted good.

Thanks Sir Simon. It never ceases to amaze me that I can just pick up the phone and order what are ridiculously obscure parts for a very old car, buy them for sod all, for example clips and nuts that hold on unique parts of chrome trim, and have them delivered from stock the next day. It's greatly appreciated.

[Mike Arnold]

It is not too difficult to make an alternator produce silly voltages if it is externally regulated. If the regulator is faulty or the wrong one or wired up wrongly then the rotor (DF+) can be fully energised by (ie shorted to) the secondary output (D+) and the thing will max out. As Ron says, dumping 55A into your battery whether it wants it or not!

I might have the terminal IDs wrong on this but they are the best that I remember.