Voltage regulator test.

Hey guys,

do you know of a way to test the voltage regulator?

Stick a multimeter on it and see if you get a reading. Should be somewhere around 13.8v


best, whit

Thanks for that.

Theres no other way that they can break? (ie. causing voltage spikes, etc) ?

The deal is the latest e34 is eating computers (if you remember that thread from before the server crash)

Well - we took it to a local BMW only shop and talked to many others - and nobody has a single CLUE of what it could be except that they say it seems like a voltage issue. Apparently the injectors and coils are all good.

We thought that maybe the voltage regulator could be spiking, or something like that - causing the ECUs to break. I think It's killed about 5 or 6 ecu's in total now.

Thanks!

Quick bump - don't want to kill yet ANOTHER ecu. lol

would act as a huge regulator, limiting significant overvoltages. Also, there are too many electronic devices in the car besides the ECU, has any one of them got fried??

Have your shop been able to identify the ECU damage?

In any case, you won't be able to test the regulator unless you start the engine. You can unplug the alternator and test without it, but guess you will fry the next ECU.

Javier

The cd changer is broke but it could or could not have anything to do with it. When we drove it with my trusty 735i's boat batrie it ran on an ecu for a long time so it could be acting as a huge capacitor... just some ideas.

EDIT:
This is the link to what the problem is related to:
http://www.bimmer.info/forum/showthread.php?t=12087

I also have an e32 w/ same exact voltage regulator should I switch the regulator from the 5 and into the 7 and then have it tested or should I switch the whole alternator? I don't mind if it fry's the 7's computer because that would say exactly what the problem is and its ecu's are only 30-40 bux as appose to 200 for the m50 computers

Being that the e32 runs on different electronics, what says that the ECU will die.. or is as sensitive?

I have heard of several cases where a bad voltage regulator has caused death to the ECU, though. I guess its sort of rare but happens to a handful of people.

Basically - at this point there is nothing that is not suspect.

If you're not seeing significant flickering of the lights, I sort of doubt that the ECU problem is regulator-related. Besides, the ECU should be able to tolerate substantial and prolonged overvoltages. I don't know to what standard BMW specifies its utilization equipment, but if you use MIL-STD-704 as a model, the equipment in the car should be able to withstand sustained long term overvoltages of 50% indefinitely. (I may be slightly off on the exact percentage, it's been a while since I used 704). If the regulator were doing that, you'd definitely see unusual light brightness and you'd be roasting the battery.

That said, you might be seeing repeated load dumps caused by an intermittent connection in the battery circuit, or in the battery itself. Load dumps can be very nasty affairs. Again, the ECU should be designed to tolerate these, but like many things, it depends.

If I were you, I'd be looking first at the battery circuit very closely, then I'd be checking the injector and coil drive wiring for intermittent connections to ground or +12V.

Well the deal with the regulator is the car hasnt ben running for more than a little bit without dying - so we cant tell if electronics are going crazy or not. It's also been daylight out - so no headlights or anything.

And: the battery has been dead for a while, so possibly due to the regulator? I have a suspicion that this whole deal is caused by the battery (oddly enough) - because we used the battery from the e32 to run the car when the loaner ECU didn't die. Every other time it has been the original battery and the ECUs keep dying.

Holy crap. No wonder you're having problems. If that battery is open, and you're essentially running without a battery, you're abusing the crap out of everything! Before you do anything else, FIX THE DAMN BATTERY! And make sure the connections to it are in perfect condition from the alternator and starter back, and including the grounding.

Well, voltage regulators are cheap so it makes sense to replace it. I think the more likely explanation is a frayed wire somewhere in the engine harness that's shorting out and causing damage. Have any of the destroyed ECUs been diagnosed?

E32 735i has practically the same electronics as an E34 535i; same goes with the 740/540. There are some more goodies in the E32, but nothing that seriously differentiates the electrical systems.

best, whit

Well i riped the alternator out and brought it down to kregan and they tested it and the voltage regulator and no problems there so there is something elts eating the ecu's

Figured it out see other post "m50 won't start"