Odd alternator behaviour

[Jon280]

Went out for a bit of a drive yesterday, and after a few minutes noticed the voltage gauge on the dash was over the end of the scale (i.e more than 16v). As soon as I pulled over, it dropped to the normal 14V, but rose again when I moved off. Stopped, killed the engine, gave it a couple of minutes, then set off again and all was fine.

What could this be? I have only ever experienced alternators not providing enough volts before, never too many. My initial thoughts would be the regulator on the alternator, being faulty, but a bit strange how it misbehaved for a bit, then went back to normal.

Is replacing the regulator (assuming its possible and available) likely to sort this, or is it new/replacement alternator time?

[maston]

Hi Jon, not that I'm an expert by any means but I think you're on the right track mate.
I say this as I had a knackered regulator on the alternator on my old mini with similar symptoms. A new one cured it.

[roseytvr]

Yep new regulator and quick before it fries the battery. Just had the same problem on my griff, £30 cash fitted by local auto electrician

[adam quantrill]

Mine has been doing this too recently so I stick on the fan which brings it back down to 14V steady.

I've been checking the battery but it hasn't consumed much water so I'm not that worried.

[mrzigazaga]

Hi Jon...I think i have a spare alternator..I will have a look in the garage tomorrow..Make sure it is the alternator ..Get a tester on it if poss to see if it is overcharging..Might be a faulty gauge..Cheers..Ziga

[ElvisWedgely]

I would check the battery terminals and make sure they are tight. Then I would check the negative from the battery down to the chassis and make sure it's sound. Then I would check the output of the alternator when the car is running. If it reads around 14.5v then that's fine. Assuming all those are ok, I would suspect a dodgy battery.

Tony. TCB

[RCK974X]

I've seen that on an old Cortina, and it was my favourite cry - "A DODGY EARTH !!"

The main earth strap was corroded, as were several body connectors. Wierd thing was car still managed to turn over, until we realised that many earth returns from the loom went to the same bolt on the body, and not via the big thick earth wire for starter to battery ...

On the other hand, it could well be a dodgy regulator in the alternator, but check all your earths first (even the alternator to engine)

[adam quantrill]

Good point - mine started after the head gasket treatment where several earths were disconnected and remade - I did check them (and clean them) but it's looking more likely to be an earth problem really.

[Jon280]

Will give all those suggestions a check, just recently had a new battery so don't really want to be frying it after only a couple of months! Will get a meter attached to make sure its not just a dodgy gauge, and also check the wiring. Though if a new regulator s pretty cheap may just change that as well as a precaution.

[Jon280]

Well, just been and had a tinker, checked all the wiring and that appears to be sound, and the voltage on the dash ties up with that from a multimeter, although I was getting a nice 14V today. Took the plastic cover off the rear of the alternator to investigate the ease of replacing the regulator, to be greeted with this...



Not a nice simple regulator as I have seen on other alternators.

Think I will just lump for a new alternator, as can get one for around £55 from Euro Car Parts, either a new RTX one http://www.eurocarparts.com/search/401590572/p/hom...
or a reconditioned Lucas one http://www.eurocarparts.com/search/401590571/p/hom...

Any benefit to getting the reconditioned Lucas one over the RTX one? (never heard of RTX...)

[Aeroflop]

After changing my regu last summer due to same symptoms, I'd blame it. It's not just simple screw-off - screw-on, but it's not that hard still. Just remove the alternator, open the plastic end, change the regu and put pieces back in.

There's two types of regus on the same part number, of which one has one wire more. That version needs an external comparing voltage, which is provided via a connector on the alternator. The less-wired version can be installed instead of this (just leave the comparing voltage out), but I don't know if it's possible the other way around.

The regu is the metallic box with 3 wires:
http://gallery.zbxt.net/k/415

The one I installed was labeled LUCAS 15TR REGULATOR PART No UCB 129 37661 AEU3076 NSN: 2920997213715, Kiila has charged really nicely since then.

Edit: agh, you already had checked the inside of the alternator (really, it's just like 2-3 screws oslt from that point you've already been), for some reason I only saw ~half of the message before I wrote mine.

Edit2: You already seem to have the 2-wire version.

Edited by Aeroflop on Friday 28th June 16:23

[Jon280]

Ahh, that makes my life easier. I was assuming it was the bit around the bottom of the alternator, and for some reason overlooked the metallic box. Have now ordered a replacement, as changing that will be a whole lot easier (and cheaper) than replacing the alternator.

Cheers!

[RCK974X]

Question, 'cos I'm interested.... is that one of the regulators with the brushes included in the unit/housing ? I've seen a few more modern ones (like the Valeo one on my Volvo) done that way....

[adam quantrill]

THe bit around the bottom is the diode pack, you have to change this if you have the other problem, namely the voltage isn't big enough.

I changed the diode pack on mine about 6 months ago - you have to take off a few more bits but it only takes an hour to do and the diode packs are about 7 quid on the Flea.

[Jon280]

Well, I have now fitted a new regulator. Found a place not a million miles away from me that were open on Saturday and had the right part for £6. (S and C Electrical in Harlow if anyone needs somewhere similar, they sell on Ebay too).

A decent drive yesterday had the voltage being at what it should be, so hopefully this has solved the problem.

[mrzigazaga]

Good stuff mate..Hopefully see you at the park next weekend then...Cheers..Ziga