Gentlemen, yesterday my car overheated, so as I opened the the reservoir cap coolant spilled all over the place. I let the car cool off, added more coolant and went on my way.
Right after, the built in voltmeter in my radar detector showed the output voltage of ~17V. If the car's at idle it drops down to 13.5-14V, but as soon as car RPM go over 1000-1500 the voltage spikes too.
I've already tried different regulators - one was Bosch from my old alternator, one was Beru brand from NAPA and both exhibit the same symptoms. I also hosed off the alternator really good hoping to wash away the dried up coolant, but it didn't help either.
My original alternator had a bad diode and the battery light was staying on with car off, so I replaced it with this used one from eBay. It's been great ever since, always staying between 13.7-14.1V, but after the overheating incident with coolant yesterday it spikes to 17V no matter which regulator I try on.
Ive researched the hell out of this yesterday and everything indicated to a bad regulator, but now that Ive tried 2 other ones I am stomped. Any ideas what to do next? Thanks in advance!
Alternator output voltage ~17V, new VR didnt fix it -_-
The field winding regulated current has to go thru the same ground path that is used by the voltage regulator to measure the D+ volts against. Unless this ground is really good these two functions tend to conflict with each other. Clean the the voltage regulator ground path surfaces mechanically (use fine steel wool or dremel wire brush). Most spray contact cleaners will not be strong enough to clean the surface of the the alternator rear cover casting where that lower regulator ground tab needs to make good connection. If there is a regulator ground eyelet it would not hurt to clean the related screw threads also.
Another overcharging possibility is an open stator to D+ diode or diode connection (not the six in the main path). Main output (red) should be measure within about a volt of blue D+, each measured with respect to alternator case ground. If D+ is lower due to weak or open diode path, the voltage regulator will command higher field current than is really needed and cook your battery with too many main output volts. Check the electrolyte levels if your battery style allows access.
If the coolant mess got as far at the battery connections, it would be good to clean them up also. Although less likely to contribute to 17 volts (I assume you can crank and start up just fine), the stray coolant can cause numerous electrical issues elsewhere and later on. In particular there is that mass of stacked terminals that bolt onto the positive battery strap lug that deserve to be individually separated, mechanically cleaned, and reconnected in the original order taking care that the restacked terminals compress flat. Since the current flow is primarily thru the surfaces, not the bolt and threads, both surfaces of each connector need to be clean, and the related battery strap lug surface needs cleaning also. All of this is in addition to the usual cleaning of both battery posts and their lug inner surfaces.
Another overcharging possibility is an open stator to D+ diode or diode connection (not the six in the main path). Main output (red) should be measure within about a volt of blue D+, each measured with respect to alternator case ground. If D+ is lower due to weak or open diode path, the voltage regulator will command higher field current than is really needed and cook your battery with too many main output volts. Check the electrolyte levels if your battery style allows access.
If the coolant mess got as far at the battery connections, it would be good to clean them up also. Although less likely to contribute to 17 volts (I assume you can crank and start up just fine), the stray coolant can cause numerous electrical issues elsewhere and later on. In particular there is that mass of stacked terminals that bolt onto the positive battery strap lug that deserve to be individually separated, mechanically cleaned, and reconnected in the original order taking care that the restacked terminals compress flat. Since the current flow is primarily thru the surfaces, not the bolt and threads, both surfaces of each connector need to be clean, and the related battery strap lug surface needs cleaning also. All of this is in addition to the usual cleaning of both battery posts and their lug inner surfaces.
Thank You Sir for a detailed response! I ended up getting a used 90A alternator from E30 with solid mounts - that did the trick!
However, after starting up the car alternator had a hard time staying @ 13V with just headlights on, and wouldn't get above 13.4V with everything off.
So I took out the regulator it came with and the brushes were down to almost nothing. I swapped it with the one I had from my first alternator (this is my third alternator since Ive bought the car, including the 1 car came with) which is Bosch and still has ~5-7mm brushes left . Unfortunately that didn't make any difference - same result.
Tomorrow gonna try yet another (new) regulator to see if that bumps the output voltage to 13.5-14V where Id like to see it.
Will keep posted, it might help some1 someday
However, after starting up the car alternator had a hard time staying @ 13V with just headlights on, and wouldn't get above 13.4V with everything off.
So I took out the regulator it came with and the brushes were down to almost nothing. I swapped it with the one I had from my first alternator (this is my third alternator since Ive bought the car, including the 1 car came with) which is Bosch and still has ~5-7mm brushes left . Unfortunately that didn't make any difference - same result.
Tomorrow gonna try yet another (new) regulator to see if that bumps the output voltage to 13.5-14V where Id like to see it.
Will keep posted, it might help some1 someday
Where are you measuring voltage, at the alternator or at the battery? If it's at the battery, try at the alt, often it's different due to resistance in wiring/connections. I'm not sure about BMW 80/90, but it's not unusual for alternators with higher maximum capacity to put out less at idle.Orxan4ik wrote:Thank You Sir for a detailed response! I ended up getting a used 90A alternator from E30 with solid mounts - that did the trick!
However, after starting up the car alternator had a hard time staying @ 13V with just headlights on, and wouldn't get above 13.4V with everything off.
So I took out the regulator it came with and the brushes were down to almost nothing. I swapped it with the one I had from my first alternator (this is my third alternator since Ive bought the car, including the 1 car came with) which is Bosch and still has ~5-7mm brushes left . Unfortunately that didn't make any difference - same result.
Tomorrow gonna try yet another (new) regulator to see if that bumps the output voltage to 13.5-14V where Id like to see it.
Will keep posted, it might help some1 someday