Turbo II

iTrader: (1)

Last Friday, warning cluster lit up. Belt was fine but heard screeching sound when I revved it sometimes. Also under 1k rpms cluster lights went out, over it they came on. Drove it home removed alternator took it to AutoZone and they said it was bad.

Took alternator to a shop that rebuilds them, they check it and said it was bad also so I left it with them to rebuild. Picked it up today, installed it and it worked fine for about 5 mins and then lit up the warning cluster and showing up to 18V output at times.

Battery reads fine, car runs great, no squealing this time from the belt (was it trying to lock up before?), just the same over/under 1k scenario and putting out way to much voltage. It was putting out anywhere from 13 to a little over 14 volts before it flipped out.

Is it possible they I got a bad rebuild or is there another electrical problem I should look for?

bumpstart

is the s5 alt mounted into a s4 harness by any chance?

Turbo II

iTrader: (1)

No, it's all original. '91 S5 Turbo N370 alternator. Just tried it again and it did the same scenario. It worked fine for 5 mins again except I noticed this time since it's dark outside and the parking lights were on so I could see the dash that around 3500 rpms or so the two lights on the warning cluster (open door and parking brake on) were fluctuating some (brighter then dimmer) as well as the lights on the dash and doors. Other than that everything was fine, anywhere from 13 to 14 volts depending on the revs until it decided to freak out again and start putting out 17 volts and the warning cluster came back on. Guess I'll be pulling it back off tomorrow morning.

bumpstart

sounds like the S terminal is getting a very poor signal
( the dash warning cluster glow up down is usually a dry joint issue through the interior fuse panel and the body CPU ,, possibly un -related )

run yourself a temporary S wire directly off the battery to the back of the alt,, this is the pin closest to the B+

( the normal wire is also supposed to be live 100 % of the time and the other white/black wire is for the dash light )

if your S signal wire is intermittant,, the s5/6 alt will try and adjust its output to the max
- even with the car not running ,, and may get hot and fail the diodes

else,, welding on the car with the battery connected will also blow the diodes

Turbo II

iTrader: (1)

Thanks for the info, I'll try that before I take it off and back to the shop. I have never seen the lights doing that before and like I said it was RPM related. Someone asked me if the voltage regulator was built inside these which I've found it is. Is that something that should be looked into if it needs another rebuild?

bumpstart

if it requires a rebuild there is definately something wrong with the L and S wiring
i would go as far as bypassing it ,, running my own S,,and ignore L
( the difference is the alt will need to lift to 3K revs before it turns on first time )

i have run these alts thus for umpteen years,, no issues beyond that need to rev to excite the field first go
( interestingly s4 alts only need to get to 1500 rpm before they self excite first time )

Turbo II

iTrader: (1)

Took it off this morning and went back to the shop that rebuilt it, of course they were closed. So I went in AutoZone down the street to have them check it and it passed twice. Told him it seems to take 5 mins or so before it starts screwing up and he said they could test it on the car to get a better idea. I'm not to thrilled about driving it around with this problem even though the store is just 5 miles from the house and not sure what they could find out.

Haven't tried the wiring suggestion yet but may give it a go before I do anything else.