orangecurry

If you do everything at the same time, you won't know what the issue was.

I'd do the VR as it's obviously failed, measure the output of course, and then do some driving. But do take the solid state DME with you in the car.

However, I have found that just taking-out/replacing the OE DME (I have two of course!) will usually make it magically work again - the physical movement re-establishing the contacts - but would fail again at some future point.

Which is why I bought the solid-state DME - though to be fair I have not yet resoldered my OE DME contacts.

95_993

Use care with the insulator on the alternator as they can easily break and are impossible to find.

https://rennlist.com/forums/993-foru...rt-needed.html

flyweight

True. However, as much as I would like to nail down the exact root cause, I prefer for this problem to go away (permanently) right now. It was quite a bit unnerving when I lost power on the 2-lane twisty mountain road with no shoulders. Luckily it happened right next to a space for cars to turn around. I shuddered at the thought of this happening go up a steeper hill on that road.

flyweight

Disappointing results after replacing the voltage regular and DME relay: similar result of 17v+ when idling measured at the battery.

What does this now mean? Grounding problems?

jay@EZimmoblock.com

Very strange. Dumb question: do you know if your meter is accurate?

flyweight

No no i was the dumb one. Borrowed another from a friend and turned out my multimeter itself is low on battery. In the picture the right one is mine. Both matched once I replaced the multimeter battery.


Now my battery reading is 13.4v idling, 12.3v when engine off, and 12.2v when engine off but headlights (tail lights converted to LEDs) on. My battery is 2.5 years old. Those numbers seem low but do they indicate my alternator is on its way out?

Heuerman

Look good to me but you need to blip the throttle to get the alternator to energise or hold the revs at 2,000 and measure the voltage which should be 14.3V

IXLR8

Actually, if the one on the right was supposed to read "voltage", you should have had the BLACK lead in the COM port.

IXLR8

Well this was at idle and that battery voltage is measured directly at the battery terminals.


The factory voltage regulator for the 993 is set to 14.5V at the alternator because of its location from the battery.

Heuerman

Yes, you would expect a drop in voltage because of the cable run from alternator to battery but anything in and around 14.3 is fine.

flyweight

@IXLR8 Thanks. That was indeed rudimentary mistakes from me.

The cigarette lighter based voltmeter told me that the voltage is 13.2-13.3v while driving, idling at 2000RPM, or just idling. Verified at the battery terminals as well.

What does this say about my alternator then?

IXLR8

I'd like to know what the voltage is at the battery, then I'd know for sure.

If all electrical connections are good, then your alternator might be the issue. Turn on more high current loads: high beams, rear window defroster, etc. to load the alternator to see what the voltage is doing.
Either a voltage regulator or a bad power diode in the diode pack. Why not rebuild the alternator if the mileage is high?

flyweight

Thanks. That makes sense. I'll measure at the battery when I get the Bluetooth voltmeter.

I'm definitely open to have the alternator rebuilt locally.

IXLR8

Well lets hope they do a good job because if it is a high mileage unit, turning down the slip rings to smooth them out (which are already quite thin when new) is a bad idea. They should be replaced. Even Bosch was and maybe still is doing that and you'd think it is a Bosch rebuild.

flyweight

Another newbie question: in what state should the alternator be delivered to the shop for a rebuild? Do I need to remove the impeller and the fan? When I replaced the voltage regulator, I couldn't even remove the impeller (it rotated) so I replaced the VR in place.