Red UFO

Can anybody translate what Wally said into English?

928ntslow

This is actually a very good post. Thanks for the info Wally. My 82 (same color as ozz) has this issue at idle and when the AC is on. At idle, voltage dips down to 10v, when the AC is on and I am at idle in gear, the voltage may sometimnes drop below 10v and my V-1 starts to spasm due to low current to the cigarette lighter. It has been doing this for a few months.

I will check the lighting and follow the procedure if it goes beyond that.

Very cool!

dr bob

The issue that started this thread is one where the altaernator fails to "light off" until the engine speed is high enough for residual magenetism in the rotor to make enough power on its own to finally self-excite. Keith, it sounds like your car makes voltage right away from starting, but that it doesn't make a lot of current at idle. This is in fact a fairly normal condition for the alternator. Performance of the alternator depends on having adequate RPM's. Alternator manufacturers rate their alternators at a certain available current, and the fine print usually states a minimum RPM for that to occur.

On to your problem: Battery. A tired battery won't sustain the system voltage without a lot of help from the alternator. Your symptoms point directly to that problem. Battery old in the '82? If you aren't convinced that the battery is the problem, do a quick check with a battery hydrometer (less than $5 at the parts store...) to see how it's holding up. Lots of us try to use a battery until it strands us. We end up sacrificing an expensive alternator trying to save a few bucks on a battery that you'll end up replacing soon anyway.

Wally published a fairly comprehensive annual electrical maintenance program that cuts down on a lot of mystery issues on the cars. If it isn't already included in that list, a quick fluid density check with the hydrometer should be added to the annual inspection and clean routine. Depending on the alternator to cover for a battery that's weak maens the alternator is working extra hard all the time. Save your alternator by replacing the battery when it gets tired, without waiting for it (and the alternator...) to die on you.

Keith, I have a hydrometer if you don't want to carry it in inventory at home. Cheap ones start at $1 or less at the Wal-Mart battery rack, the one with the little floating *****. The more deluxe unit has a calibrated float that tells you the actual specific gravity of the fluid. Less than $5 last time I looked. You may need to go to a high-end place like NAPA to get the better one. The cheap one will do the job fine, though, and takes up less room in the toolbox when not in use.

HTH!

928ntslow

Thank's Bob, but battery is fairly new and recently tested well. Alternator has been replaced with in the last year and charges just fine. Idle is set to 750rpm. I guess I didn't mention that the "charge" light does NOT come on in postiion #2 in my post. Before I do anything else, that bulb is getting replaced! (I need to order some oil filters and other little tid bits for the 82 anyway).

I will certainly report back after the bulb is replaced. Thanks!

Big Dave

Can anyone snap a pic of their alternator light? I don't see one, and I'd like to know where I should be looking.

Sorry for the silly question.

Garth S

No such thing! The red light in question is at the lower scale end within the voltmeter - it illuminates a narrow slot with the ign. key at position #1. ( when the entire pod blazes red in all the icon spots).

SharkSkin

Dave, get a strong light, like a 60-100W droplight and shine it on the cluster. You should be able to make out the various lights this way.

Brian B

All of this made me check out my instrument cluster. My alternator light is really dim. I guess its time to get in there and check things out...

porsche928freak

keeping you guys updated, i ordered a new ignition switch so let's see how it goes, i will get it on tuesday, another question do you guys have a picture of the pin 14 ? i checked the cables on there and some of them seems to be craked and corroded, when i was replacing the cables a couple of pins went out from the connectior and i need the order, thanks again you guys in advance, this post is getting really cool and hope all the info here helps a lot of 928 freaks

OZZ

Apoc

Hmm, interested in this one. My 79 doesn't start charging until about 2000 rpm, but then it's fine,a dn the little red light at the bottom of the alternator scale is on all the time.

Steve

SteveG

So yesterday I had the batt act up on the Sienna. Hot weather, using A/C a lot, must have put too much demand on the alter, batt was perhaps 5 years old. The hygrometer (cheap) showed each cell to be good. Voltmeter showed 10.6. Sears quick test showed it as bad. I thought the hygrometer was the more accurate method. I'm getting the $5 hygrometer and checking again, just to try and understand this procedure. Batterys are tricky.

Big Dave

I'll have to check for the light on the alternator gauge. If it's out, it'll be time to dive into the pod...another first in my 928 ownership.

Good thread!

docmirror

Steve (Apoc). It's not working right if the light stays on. You are getting a sympathetic volage on the rotor to keep the alternator running. Who know's where it's leaking in from. The circuit on the early cars is dead simple. If the light is on, the 12V to the D+ on the alternator isn't getting voltage.

SteveG

I hope you don't have a hygrometer, but have a hydrometer. That's for checking the specific gravity relative to pure water which is 1.000. Now, lead acid batteries have a simple failure mode, it is the typical loss of acid which will show up on a hydrometer bought from Pep Boys as the red ball or yellow ball in the fluid(just read the directions). This failure mode results in the glazing on the battery plate from age. The lead takes on O2 from the Sulphuric acid and it becomes PbO2(lead peroxide). This glaze on the plates reduces the current storage capacity and that's why the load test at the shop fails. It won't produce large amounts of current for starting like it should. The voltage might be up near 12V, but the current supply is minimal.

Roger and I troubleshot this issue in a matter of 30 minutes with the pod off and the cover off the fuse board. You need a ohm meter and a length of wire.

Locate the 14 pin connector just aft of the jump start lug on the pass side fender.

Pry off the plastic cover and find pin one, which has a blue wire with a white trace.

Measure the voltage with the key off; 0V.

Key on, do not start; Approx 12V. LEAVE THE METER ON PIN ONE!

Start the car, just at idle, watch the voltage on pin one. It should go up to near 13V. You are looking for a trend here, not absolute voltage.

If it does this, the circuit is good to that point, and should be okay down to the D+ connector on the alternator. If it doesn't work like it should as above, you will need to trace back the problem to connector Z on the fuse board, then follow it back to the pod connector. And ultimately to the ignition switch 12V bus.

If you don't have the WSM this is going to be hard. With the WSM it's a snap. This circuit HAS to work for the alt to charge. If you want to try bypassing things, you can use a jump wire from the jump lug to pin one of the 14 pin connector. Don't miss and hit another pin! Let the car idle, and watch the voltmeter as you jump the 12V from the start lug to pin one. The voltmeter should go up to about 13Vwhen you jump the voltage to the pin.

Doc

dr bob

Hydrometer test is to be used with the battery at full charge. If the battery won'r take and hold a full charge then you don't need the hydrometer to tell you that it's bad. The hydrometer test is there to tell you about a battery that's losing capacity. Charge the battery, move the matal and salts back into the plates as much as possible, then test the fluid again. Read the directions that came with the tool, brother!

The 'expensive' $5 gauge won't tell you any different from what the cheapo gauge does, except that you'll be able to read a specific gravity value off the float, instead of seeing that two red ball and two yellow ***** are floating, but no green balss so the battery must be tired.

porsche928freak

keeping you guys updated, i changed the ignition switch today, and fixed all the wirings going to pin 14 (the one under the hood at passengers side), the alternator is charging like a champ, the gauge moves up almost at idle speed not like before at 4000 rpm, the only thing that still is not working are the lights at position 1 (ignition) any lights are showing except for the stop lights , what do you guys think can be the problem??

And also a big thank you to all of you helping me on the alternator problem

ozz