Pesky electrical question

Britt · 03-12-2002, 02:49 PM

Alright, I dropped my engine and transmission about a month ago. I finally have it all back together but the starter will not crank. I debugged it down to no voltage at the big input wire on the starter. I put a jumper wire (made up of two sets of jumper cables) on it and the motor starts. I figured maybe I messed up something on the alternator and took it off to check. Nothing appears to be out of place. The jumper test shows me the starter is working. I am now tracing the wire (big red one) from the starter to the 14 pin connector which is on the driver's side in engine compartment. I pop the connector off and start tracing continuity. I have connection between pins 2 and pin 14 on the connector (female side which is the wiring loom going to the starter and to the red wire in the alternator (B+ lug I think). I then get out my voltmeter and leave the connector unplugged. Carefully turn the key to the ON position and don't find 12.5 volts only either of these pins.

I traced a few of the wires on this connector and here's what I found -

On engine harness female-side connector -

Pin 1 - Ground Pin 2 - Starter (lug 30) Alternator (B+)
Pin 3 - Oil Pressure Warning Lug Pin 4 Oil Pressure Sensor
Pin 5 - ?? Pin 6 - ??
Pin 7 - Skip Pin 8 - ??
Pin 9 - Ground Pin 10 - Skip
Pin 11 - Blue Alternator (D+) Pin 12 - Skip
Pin 13 - Brown Alternator wire (Gnd?) Pin 14 Starter (30) Alt (B+)

Key ON reading voltages on the male (Car side) of the connector -

Pin 1- 11.63v Pin 2 - 0v
Pin 3- 7.43v Pin 4 - 7.74v
Pin 5- 11.84v Pin 6 - 0v
Pin 7- Skip Pin 8 - 10.72v
Pin 9- 11.83v Pin 10 - Skip
Pin 11- 11.83v Pin 12 - Skip
Pin 13- 0v Pin 14 - 0v

The skips mate so the connector is not backwards or anything taht silly. I am totally confused as to why the Ground pins look to have voltage on them. This is a floating (ie - not connected situation as the ground connector is on the other side of the connector (behind the alternator).

Does anyone know what the pins of this connector should be connected to? Do these voltages mean anything to any of you? I had the wiring loom pulled to the side when I was washing the engine compartment. The other piece of info I have is that the engine ran for a second or so (then I shut it off) when I did the jumper test on the starter. I could not find a wiring diagram in the Bentley or the Haynes manual (don't have the factory manual).

Clues? Help? Ideas? Anything?

Thanks in advance.
britt
86 Carrera

Britt · 03-12-2002, 03:35 PM

Pin 1 on the engine harness side actually goes to the Starter (terminal 50) not Ground.

More questions which may relate. -

Alternator wiring

Can anyone confirm -

B+ Lug goes to big red bundle of wires (~5 or so)
D+ Lug (which has a shielded blue wire coming off of it on the alternator connects to the Blue wire on harness which then goes to Pin 11 on the engine harness side of the connector.
Brown wire (goes to Pin 13 on connector and a Ground wire bolted on case) connect to the other alternator lug (which ohms to the case of the alternator.

This all seem correct?

alan911 · 03-12-2002, 03:38 PM

Try this. Different year, but close wiring set-up.

http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=61555

Looks like your Pin #2 is the problem. From what you described, with ign. on you should get the 12V with a probe on #2 pin on the car side, and the other probe to chasis ground. This should go through the connector to the starter. You're getting -0- Volts. Athough the starter actually should be on Pin #1, typically Yellow.

Hard wire Ground connections are Brown and there is no need for a ground through the 14 pin connector. That's what the braided chasis straps are for and why they are very important.

You'll drive yourself nuts on the voltage for the pins as some are not live until the enging is actually running i.e. the sensors and stuff. And some are only acitive during the starting cycle. And some are not even connected to anything on the engine. Plus you will get no readings from the Alternator connections (charging circuit) back to the battery while the connector is disconnected as another example.

Your ???s after the pin #s are because those pins are only used if you have certain equipment like Tip-tronic stuff as an example. Typically, 2-7-8-12 are not used- on the engine side but are indeed there on chasis side.

This info is for my '77 so take it with a grain of salt.