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General Information => General => Topic started by: TTH on April 18, 2008, 08:22:35 am

Title: 1993 Passat TD alternator question.
Post by: TTH on April 18, 2008, 08:22:35 am

I recently changed my waterpump, and upon assembling everything, the tach will not work.  At around 100 kmh in 5th the tach will bounce to 1000 rpm and back down, and the battery light will come on intermittently.  With the car shut off, battery voltage is a little over 12 volts, and with the car idling, voltage stays the same at times, and sometimes jumps up a little.

Is the alternator on the way out?  Did I miss a wire somewhere when I reinstalled it?  I only have one red wire that runs to the W terminal on the alternator.  I didn't see any others, but am wondering if there is one tucked away somewhere.

The belt never squeals, so I don't think it would be belt tension (serpentine).

Title: 1993 Passat TD alternator question.
Post by: burn_your_money on April 18, 2008, 08:26:35 am

I'm not overly familiar with the B3s but is there not a blue exciter wire? You did hook the big red cable up right?

Title: 1993 Passat TD alternator question.
Post by: TTH on April 18, 2008, 09:26:39 am

The big red cable is hooked up (to the W terminal).  I didn't see a blue wire, but will take a look when I get a chance.

Title: 1993 Passat TD alternator question.
Post by: Vincent Waldon on April 18, 2008, 10:31:44 am

The voltmeter is telling you your alternator is not working.... so neither will your tach.

In order to work correctly the alternator needs:

1) B+  a heavy duty wire (usually red from a big terminal on the alternator to the battery

2) D+  a thin, usually blue wire that runs to the ALT light on the dash and provides excitation voltage to the alternator

on diesels there is also

3) W  a thin, usually red wire, that provides RPM info to the tach and oil pressure warning system

On the serp alternators the D+ and W signals are usually on the same harness and plug into the alternator while the B+ bolts onto a stud.

Sounds like your alt might be a bit different ??  Or perhaps you forgot tp plug in the smaller harness with the D+ and W wires ??  Post a picture if you get stuck ??

Title: 1993 Passat TD alternator question.
Post by: TTH on April 26, 2008, 11:23:32 am

Thanks for the help guys, I figured out my mistake.  When I assembled everything, I noticed that two wires split from the harness (including) the blue, and I plugged that into the A/C compressor.  When I looked at the alternator closer, I noticed that there was an empty connector on the bottom that I missed when I buttoned everything up  :oops: .  After I moved the connector over, everything worked fine.  Thanks!

I don't know what happened to the A/C harness.  The previous owner removed the A/C lines, so he probably whacked away some of the harness as well...

Title: 1993 Passat TD alternator question.
Post by: jtanguay on April 26, 2008, 08:18:46 pm

Quote from: "TTH"

Thanks for the help guys, I figured out my mistake.  When I assembled everything, I noticed that two wires split from the harness (including) the blue, and I plugged that into the A/C compressor.  When I looked at the alternator closer, I noticed that there was an empty connector on the bottom that I missed when I buttoned everything up  :oops: .  After I moved the connector over, everything worked fine.  Thanks!

I don't know what happened to the A/C harness.  The previous owner removed the A/C lines, so he probably whacked away some of the harness as well...

i wonder if there was enough juice running to actuate the a/c clutch  :lol: glad to hear the problem is fixed :)