924Board.org

[CalGuy]

Hello,

The voltage output when running at 2000+ RPM is yielding an output of 18+ volts (using a voltmeter at the engine).

I have changed the battey and the alternator with new ones but the output is still too high. My guess is a defective voltage regulator inside the alternator. Any ideas? Could it be something else?


Any help is greatly appreciated.

Thanks
_________________
-CalGuy
1980 924
1992 968 (Newest edition dubbed 1BAD968)
2001 Range Rover HSE

[DOCO]

probally the regulator,but i would replace the alt. not just the reg.
_________________
Doco "where am i going and why am i in this handbasket"author unknown
79 924 N/A "Webster"
_______
/______\
[+]___[+]
\0 924 0/
[__]..[__]
"WEBB STR"

[ideola]

Definitely a defective regulator.

I've had three OEM Bosch alternators fail on me in 2011, all of them due to voltage regulators. When it failed on the 937, it took the starter and the fuel pump with it. The day before our party to celebrate its home coming. That was embarrassing.

Take the alt up to your FLAPS and have them test it to be sure.
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erstwhile owner of just about every 924 variant ever made

[gerben1986]

I also think that your regulator is gone. But why didn't you check that first before replacing the battery and altenator? They are much more expensive then a regulator (€ 16,-/$20 I guess).

[CalGuy]

Thanks guys for the responses. I believe the voltage regulator is inside the alternator, is this true? If so I'll install another new alternator and return this new one which is clearly defective. The battery was also dried so that's why I replaced that one. Is there a recommended alternator? The new and old ones are both Bosch.
_________________
-CalGuy
1980 924
1992 968 (Newest edition dubbed 1BAD968)
2001 Range Rover HSE

[RC]

If you are REALLY getting a reading of over 18VDC on an accurate meter, then agree that the regulator is faulty. However, is unlikely that a new alt will also have the same fault. Perhaps before you possibly embarrass yourself returning a good alt, use another known good meter on the DC setting (20V or more) to verify the reading.

Regs are mounted externally at the rear, held by 2 screws, and easy to replace. May not be easy with the alt mounted though.
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World`s quickest 924 2L slushbox

[!tom]

I can't see how an alternator at idle could possibly generate enough current to get the voltage that high at the battery. Either your battery is extremely faulty along with your alternator(s), or your meter isn't giving you an accurate reading.

I agree with RC here, but would like to add that the current necessary to see 18 VDC at the battery would likely be beyond what your alternator could supply, in particular if you have a good battery.
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78 924 NA
5-lug

[Smoothie]

+1 on the whole voltage regulator thing, but if that doesn't pan out-
Another possible scenario... While doing my own bench testing of a bosch alternator a few years ago, I found that my voltage was within range if testing with a battery in circuit. -But with the battery removed, voltage shot up to over 20V. Put the battery back in-circuit and voltage went back to normal.
-Sooo I'd suggest that possibly your wiring is bad, specifically between the battery and the alternator, leaving the battery out of circuit with the alt.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[stevekat]

If you had +18V with your old alternator, and have +18v with a new alternator, and possibly a new battery at the same time, I highly doubt it's your alternator or regulator (if a different regulator came with the replacement alternator.

So I am with RC and Itom, that I suspect it is your meter, or the setting your are using on your meter (make sure it is DC volts.) Smoothie has an interesting prior observation, so if your meter is found to be good, I'd go that direction.

(BTW, I used to hear that pulling the battery out of the circuit would fry the diodes or other components of an alternator. I don't know if this is true, an old wives tale, true in some circumstance with some system designs, or just makes it more likely, but I'd be careful with possibly disconnecting the battery.)

Dan, you voltage regulator on a OE or Bosch Factory rebuilt alternator went bad? Was it a Bosch stamped regulator? It fried your starter? What did it do to it? What let you to discover the issue? You then went to a non-Bosch alt/reg?
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

[CalGuy]

Hey Guys,

Thanks for the responses. I tried a couple different voltage readers and made sure it was in DC volts. The alternator at idle is within range (about 12.6 volts); it's shoots up when the engine is revved above 2,000 rpm or so. I'm pretty sure the reading is acurate because once I rev the engine with headlights on and AC on and defrogger on (or even if all that is off) the OXS unit underneath the steering column makes a high resistance noise (posted on another thread) and all the interior lights are unusually brighter than normal (they light up as much as my newer car) and I know that's not normal. Also the power windows seem to go up and down a lot faster than usual and the blower fan inside is higher. To me these all seem like signs that the power output is high.

Smoothie that is an interesting observation regarding the wiring. Visually all looks well but it won't hurt to check for continuity, so I'll be sure to check that between the alternator and the battery.
_________________
-CalGuy
1980 924
1992 968 (Newest edition dubbed 1BAD968)
2001 Range Rover HSE

[ideola]

One thing to add to this...if you remove the battery from the circuit while the car is running, it will almost always fry the voltage regulator (I speak from experience on this matter !). So if Smoothie's hypothesis turns out to be true, and there was a fault in the wiring between the alt and battery (which is a common occurrence with the location of the NA wiring harness), it's possible you toasted the new voltage regulator shortly after installing the new alt.
_________________
erstwhile owner of just about every 924 variant ever made

[CalGuy]

Ok! So I tested the alternator at two different stores today and both indicated that it was in tip top shape (regulator, too). So I also checked for continuity in the wiring, no faults there. Then as I was installing the metal shroud backing to the alternator I checked for grounding and it was giving a signal!! So I found out that the bolts anchoring the metal shrouding were touching on the inside of the alternator basically in effect short circuiting the entire flow! So I went ahead and added some washers to the bolts and presto everything works cherry. I revved the engine for a little bit (did not drive the car) turned on all the lights, defroster etc and the volt reading was within range.

Thanks guys for all the help! Now time to tackle the running lean problem!
_________________
-CalGuy
1980 924
1992 968 (Newest edition dubbed 1BAD968)
2001 Range Rover HSE

[CalGuy]

Ok! So I tested the alternator at two different stores today and both indicated that it was in tip top shape (regulator, too). So I also checked for continuity in the wiring, no faults there. Then as I was installing the metal shroud backing to the alternator I checked for grounding and it was giving a signal!! So I found out that the bolts anchoring the metal shrouding were touching on the inside of the alternator basically in effect short circuiting the entire flow! So I went ahead and added some washers to the bolts and presto everything works cherry. I revved the engine for a little bit (did not drive the car) turned on all the lights, defroster etc and the volt reading was within range.

Thanks guys for all the help! Now time to tackle the running lean problem!
_________________
-CalGuy
1980 924
1992 968 (Newest edition dubbed 1BAD968)
2001 Range Rover HSE