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Not sure if this is the the true issue I am having, but the voltage regulator is suspect, as when i increase the RPMs the voltage increases as well, sometimes over 15V, which then shuts off the radio.
So far multimeter tests at the radio indicate high voltage at times and the dash indicator matches that as well. will test at the battery post too.
I know that the voltage regulator is attached to the alternator, and I believe it is positioned at the bottom front of the engine on the driver's side. I was wondering if I had to replace the voltage regulator, could I do it without removing the alternator. It looks like it just screws in, but I have no idea.
It screws onto the alternator body inside the cover, but it might depend on the alternator model, and it could be inegral with the brush holder. Either way it would be pretty tight for space to work in there, unless you have access to a hoist. Also , if this part has failed, whats the state of the rest of it - bearings, commutator etc ? Do you want to be going in there again soon ? I would get a refreshed and tested one fitted if it was me. I had mine off while doing the belt 12k mi ago, thought I should replace the brushes, couldnt get any, put it back in. Still waiting for it to play up...
You can replace the voltage regulator on the Bosch alternator with the alternator installed in the car. Disconnect the battery ground cable and isolate, remove the shroud from the alternator, then remove the two screws holding the voltage regulator/brush holder to the alternator. Installation is reverse of removal.
If you can see the nut, it should be accessible with a 1/4 drive 8mm socket(5/16"). I have a double ring spanner in 1/4"+5/16" with cranked ends that is invaluable getting to recessed nuts/bolt heads like these.
This is mine! https://www.henchman.com.au/41441620...16-inch/pd.php
jp 83 Euro S AT 57k
Usually, replacing the regulator is a good excuse to remove, disassmble, clean and inspect the rest of the alternator. Regulators seldom fail on their own, and are more typically a victim of another fault in the system. That's usually worn brushes and slip rings, but may also include diode or winding section failure. The brushes are part of the regulator assembly that will be replaced. But they do ride on the copper slip rings, so when the brushes are worn it's likely the slip rings are too. Noisy or worn bearings allow vibration in the rotating part that will eventually destroy some winding connections and/or insulation. A worn set of brushes and/or slip rings cause less excitation current to actually pass through, causing the regulator to increase voltage to try and overcome that resistance.
Having the whole thing apart offers an opportunity to replace at least the drive end bearing, test the diodes to make sure none are failed, and get all the accumulated oil and crud washed out and away so it will cool better. Maybe even a new belt.
warning I strongly suggest that you only use a Bosch regulator to replace the regulator in your Bosch alternator
otherwise there's a strong possibility that the voltage regulator will cause the alternator to output more than the desired voltage of 14.2 or less
if that happens the next possibility is that your computers can be damaged as can other parts of the electrical system
a Bosch regulator cost quite a bit more but it will provide trouble free operation
My 88 S4 suffered a cooked LH computer due to a bogus aftermarket regulator it was outputting 18.7 volts
the battery can absorb some of this extra voltage , but it will eventually boil the battery
Thought I read somewhere that upgrading voltage regulators might be prudent with AGM batteries as they need to see a higher voltage to charge. I'm sure I read it here but cannot find it. If this isn't a thread hijack, I'd love to understand if there are Bosch Voltage Regulators which are supposed to be used.
Thought I read somewhere that upgrading voltage regulators might be prudent with AGM batteries as they need to see a higher voltage to charge. I'm sure I read it here but cannot find it. If this isn't a thread hijack, I'd love to understand if there are Bosch Voltage Regulators which are supposed to be used.
There is a modification to this style of Bosch voltage regulator talked about fairly commonly on the '80s Mercedes and BMW car forums to allow charging the AGM batteries, which involved adding a diodes on the regulator to offset the sense voltage be 0.6v.
You could also use a germanium diode for a 0.2v/each bump, if a smaller offset was desired, I suppose.
While I agree with all The above advice, I prefer a Bosch regulator and alternator rebuild is a good idea WYAIT. I have a free voltage regulator if you want. It was the one that was installed in my alternator when I had it rebuilt by a local “Bosch authorized” center. Since I had new Bosch regulator I swapped it.
do you want this one?
Last edited by Michael Benno; 07-06-2019 at 08:04 PM.
warning I strongly suggest that you only use a Bosch regulator to replace the regulator in your Bosch alternator
otherwise there's a strong possibility that the voltage regulator will cause the alternator to output more than the desired voltage of 14.2 or less
if that happens the next possibility is that your computers can be damaged as can other parts of the electrical system
a Bosch regulator cost quite a bit more but it will provide trouble free operation
My 88 S4 suffered a cooked LH computer due to a bogus aftermarket regulator it was outputting 18.7 volts
the battery can absorb some of this extra voltage , but it will eventually boil the battery
^^^ THIS
Stan is 110% correct here, as I had the exact same issue...produced by a KAE voltage regulator. And the same issue was repeated with three other KAE voltage regulators with Capt. Earl and I were able to diagnose the issue.
The design of the KAE regulators are not accurate enough, so both brushes don't sit correctly. What you will notice is that at low RPMs (under 3, 000), the alternator performs exactly as it should, outputting the correct amount of voltage.
However, if you get above 3,000 (or to the point that the rotation in the alternator cannot create a clean electrical flow due to one of the brushes being over compressed do to poor fit) the voltage will surge repeatedly. The symptoms you may see are certain electrical system cutting out like the radio, headlight beams pulsing along with other lights, etc. What you wont see is the destruction of your computer which will happen over time, requiring a rebuild, as well as probably some fuse/relay replacements, which if you are lucky, will happen at Frenzy with experts like Stan, Sean, Pete and others around to save you.
Altogether the cost of the KAE + repair costs will outweigh the cost of the Bosch regulator replacement.
12-25-2013, 04:58 PM
Voltage Regulator Replacement
