repeated voltage regulator failure

[Birdseye]

I've been suffering some difficult to diagnose electrical problems - see http://www.ybw.com/forums/showthread.php?411656-a-puzzle-for-the-elctronics-guys&highlight= if you are interested. In the end , fitting a new voltage regulatoir to the alternator has cured the issue. But thats for the moment because when I looked in my junk box I founfd that I had replaced the regulator on my alternator 4 times in maybe 3 years at the most. And always with the same symptoms of irregular cutting out causing a beep from the alarm and the tacho jumping

So. What can cause such regular regulator failures. I have checked alternator mtemperature and whilst I think that the 88C is high, people in the know tell me that it isnt.

 

[pvb]

That's a lot of regulators. Are you buying OEM regulators or copies?

 

[Birdseye]

copies. but then the alternator is a copy.

 

[pvb]

Might be worth trying a genuine regulator.

 

[pampas]

carefully check the earth/neg back to the battery+ also +. sounds as though you have a intermittent open circuit. by pulling on each cable connection as the fault if any may be in the crimped/soldered connection, or just a high resistance in the pathway.

 

[Spyro]

Do you have a 1-2-1 switch that could be causing an open circuit when switing between batteries? i.e. breaking before making?

 

[pvb]

Do you have a 1-2-1 switch that could be causing an open circuit when switing between batteries? i.e. breaking before making?

That might damage the diodes, but unlikely to damage the regulator.

 

[VicS]

That might damage the diodes, but unlikely to damage the regulator.

Isn't the regulator also likely to be damaged by a surge ?

 

[William_H]

Is the regulator one of those that is built into the alternator end plate and carries the brushes? if it si then there may not be much you can do. If however it is a separate item then it should be easy to extend the wiring and bring it out to a cooler place outside the engine compartment.
Simplistically a regulator consists of a pass transistor wired to carry current from the field supply, diodes or ign light to the brushes to earth. Or possibly the a pass transsitor is in the path brushes to earth. (sometimes described when fitting smart regulators as +or -ve regulation.)
The regulator is fed with a sample of the battery voltage which is compared to a reference (zener diode) which then controls the conductance of the power transistor. Thsi might be pulsed on and off rapidly but the end effect is the same.
I wonder then if you can't set up a bench test rig at home to check the old (dead) regulators to find if they are faulty and if so in what way. They do use discrcreet component which can suffer from heat. But generally are very reliable. good luck olewill