Why is my alternator doing?

[dugcat11]

I'm new to this forum and to the world of 944s. I've loved them ever since they appeared but just recently took the opportunity to own one. Mine is a high mileage, one owner 1984 model (black with cookie cutters).

One of the small problems I've noticed is that my alternator idiot light seems to give off a slight glow - nothing like the full-on of the parking break warning or other warning lights.

No, when driving at night, it just gives off a faint glow. I had to drive it home from Phoenix to Denver and with the prospect of going bust somewhere in New Mexico before me I decided to take it to a Porsche shop in AZ. They took a look at it and decided that the PO had put in head light bulbs that took too much juice so they put in OEM spec bulbs to reduce the load.

This did not solve the problem as my idiot light still gives off a faint glow. Any ideas? Is the belt just loose? Do other 944s have this problem?

[dugcat11]

By the way, I failed to mention that the Porsche shop in AZ did check to make sure the alternator was doing a proper job of charging ... no problems revealed. However the slight glow remains.

[SoCal Driver]

The "control" of the instrument cluster generator warning light is directly from the alternator. The light has the battery on one side and the alternator on the other. As long as the alternator is putting out as much or more current than the battery the light stays out.

The only replaceable component on the alternator is the regulator -- about $25 for an adjustable one.

14.1 vdc is a good charging voltage for the 944.

The "test" for the alternator body is to dead short past the regulator and see if there is at least 15 vdc at the larger terminal. Don't do this test for long as you can burn things up.

I would also clean and tighten all of the grounds between the battery and the chassis and the engine block.

When was the last time the timing and counter balance belts were inspected let alone replaced?

[todwic]

These are the firstest things I bought when I got my 944, and my first $1200 repair bill:

1. Haynes manual
2. metric socket/ratchet set (craftsman)
3. metric wrench set(Husky from Home Depot. I have since bought another set, since sometimes you just gotta have another wrench of the same size. I went Stanley for the second set, and I've been more happy with them. They are similar in quality to Snap-On, at 1/4 the price. but I digress)
4. Digital Multi-meter

I highly recomend you do the same if your gonna do much home mekinikin.

With your handy Multi meter, you can see if your battery is losing charge, if your alt. is charging enough, if any one acc. is causing undo drain. I have after market headlights on my car and have had no real problems. Point is, if everything is getting the volts that it needs and your alt. is keeping your batt. at a happy Voltage (14.7 I think is ideal, at least that is what my mechanics teacher told me). What I'm tring to say is, if it ain't broke, don't fix it.

[mike944]

A very faint glow is normal. As socal said, the light is connected between the alternator output and the battery. If you alternator is putting out 14.7 volts, and your battery is at 12.5 volts. 14.7-12.5 = 2.2volts just about enough to create a faint glow in a 12v bulb. It could possibly point to either a battery that's on it's way out, or an alternator that's overcharging.

Mike

[SoCal Driver]

Originally posted by todwic
These are the firstest things I bought when I got my 944, and my first $1200 repair bill:

1. Haynes manual
2. metric socket/ratchet set (craftsman)
3. metric wrench set(Husky from Home Depot. I have since bought another set, since sometimes you just gotta have another wrench of the same size. I went Stanley for the second set, and I've been more happy with them. They are similar in quality to Snap-On, at 1/4 the price. but I digress)
4. Digital Multi-meter

I highly recomend you do the same if your gonna do much home mekinikin.

With your handy Multi meter, you can see if your battery is losing charge, if your alt. is charging enough, if any one acc. is causing undo drain. I have after market headlights on my car and have had no real problems. Point is, if everything is getting the volts that it needs and your alt. is keeping your batt. at a happy Voltage (14.7 I think is ideal, at least that is what my mechanics teacher told me). What I'm tring to say is, if it ain't broke, don't fix it.

Don't forget the 3/8" drive electric torque gun/motor!

Get's you into trouble.

[SoCal Driver]

Originally posted by mike944
A very faint glow is normal. As socal said, the light is connected between the alternator output and the battery. If you alternator is putting out 14.7 volts, and your battery is at 12.5 volts. 14.7-12.5 = 2.2volts just about enough to create a faint glow in a 12v bulb. It could possibly point to either a battery that's on it's way out, or an alternator that's overcharging.

Mike

Could stop the glow with a hefty diode or two. Don't see any in the circuit diagrams.

[dugcat11]

Thank you for the expert replies. Regarding whether the timing and counter balance belts were inspected or replaced, based on the receipts the PO gave me, the following items were done 5000 miles (and 18 months) ago:

1) Timing Belt Replacement and front end seal (included a new camshaft drive belt and a new auxilliary shaft belt)
2) Major Maint. Tune-up.

Then at approx. 500 miles later:

1) Adjust cam and aux drive belts.
2) New battery and ignition switch.

I'm very happy with the car. As I want to restore it and keep it for the forseeable future, the suggestion regarding the tools and the meter sounds like a good investment.

I'll run a few tests once I get the meter.

Thanks again.

[todwic]

Then you may be interested in a couple other things I have found quite handy:

1. Screwdriver set (one with shorties for the dist. cap dogs)
2. Craftsman sells a tiny wrench set sizes 4mm to 11mm (or 10mm or 12mm, I forget the big size)
3. Feel free to add tools, needed or no, as wife allows