Early 944 Fuse box Wiring and Charging System warning light

[944noob]

I had to pull the fuse box out of 944 to clean up some corrosion. I took pics along the way so that I would be able to hook all the electrical back up, but I'm thinking I missed something... Everything is back together, but now the alternator light is on and the system isn't charging. Everything looks good behind the dash so I'm guessing the problem is at the fuse box. Does anyone have a diagram to show where and how the charging system warning light is routed? I need to know if I inadvertently unplugged something or if there is a "real" problem somewhere. Thanks!

[John_AZ]

Originally Posted by 944noob

Does anyone have a diagram to show where and how the charging system warning light is routed? I need to know if I inadvertently unplugged something or if there is a "real" problem somewhere. Thanks!

You can follow the tiny blue wire from the alternator to the dash lamp. This is the alternator "exciter" wire and is required for the alternator to charge.

This is the circuit diagram...



The POS Battery wire connects to the B+ alternator wire at the starter terminal.


Gl
J_AZ

[944noob]

Thanks! What do T1a and T1 21 stand for? Is one of those a location at the fuse box that I might have accidentally unplugged?

[John_AZ]

T1 is a typical wire connector---a means it is near the fuse /relay board.

Poor quality WSM Electrical hand held scanner page scans:






GL
J_AZ

[944noob]

Thank you so much! This will make finding the problem much simpler.

[Slam]

Also do a check of the garden variety spade connectors/wire routing on the back of the fuse block. The plugs are pretty idiot proof but it's easy to attach the one-off wires to the wrong spades.

Save John some work - the wiring diagrams are all here on Pelican ;>)

[944noob]

Where would I find a diagram that shows me which spades the one-off wires should be attached to? I just did some digging and found the diagrams John was kind enough to post, but I don't see anything that lays out the back of the fusebox.

[Slam]

fuse panel

IIRC the plugs are A to E (or so) and the spades are numbered. I know, not really helpful. The spades are labeled right on the fuse block but does it ever suck trying to read the letters upside down under the dash. Those letters correspond with the letters at the top of the wiring diagrams.

fuse panel help

There's a better link!

And finally, the Haynes 924 manual has FAR better info and diagrams than the Haynes for the 944.

[944noob]

I finally got some time to work on the car this evening and I found that the problem most likely has to do with the circuit going through fuse 12. I checked for continuity on the blue wire all the way from the dash to the alternator and it checked out so I started looking forthe source of the 12 V that the blue wire is supposed to carry. I'm still not totally certain, but it appears to be at least related to the wire that carries the current from the dimmer switch. I say that for two reasons:

1. My dash lights are out and when I power probed the blue wire the alternator started working AND the dash lights came on.

2. The wiring diagram shows the power wire for the instrumentation wiring at least being tied into the 12 V source for the charging system indicator light.

So that leaves me with two questions. 1. Where does the black wire coming off the lower left corner of the instrument cluster on Part IV page 2 go? (page 1 and page 2 don't cover the entire diagram there's a small sliver in the middle thats missing) 2. Why would fuse 12 not be receiving any voltage? I checked it top and bottom, headlights off and on and there's no voltage present. All other fuses appear to be getting juice as expected.

[944noob]

So I decided to gamble on a new alternator just so I could rule it out. The problem is not the alternator... I hate to have wasted the money, but at least I can take that off the list of potential problems. I'm considering pulling the fuse block to see if I can make heads or tails of this. I've practically got the wiring diagrams memorized and I can't seem to come up with any reason for this. I have a nice bright light on the charging system light so I know that its getting voltage, I know that the blue wire is has continuity to the alternator, and I know that the alternator isn't charging. What am I missing?

[944noob]

The problem was a bad connection on the back of the fuse block for the 2 wire connector that feeds the dash lights. Go figure...