cruise98

This is weird. Electrical diagnosis always drives me nuts.

The blue wire goes to the alarm control unit, and is also connected to the G2 relay through fuse 18. Since you have no alarm, i guess this is bridged in the factory harness somehow. Actually, the way I interpret the diagram, relay G2 closes with the key on, and energizes the blue wire to "excite" the alternator field.

Check for continuity of the blue wire at the alternator from relay G2 fuse panel position 87 IIFRC. I think something is wrong with the circuit of the blue wire. Does position 30 on G2 have 12v?

David Floyd

13.1

12.8 ignition on

can't get a pic while installed, anybody have an old alternator to show the noise reducer?

David Floyd

No continuity at 87 or 87a and position 30 reads -13.3, battery reads 13.1v at same time

Battery read 13.3v (charged overnight) as I left home this morning, 35 miles, 5 starts no headlights no a/c or wipers, battery reads 11.8v upon returning home

Dash guage tends to read 1 volt less than actual

Tom M'Guinn

13.1 what, amp? With the ignition off? You should be down in the low mA range.

David Floyd

That was the volt reading across the battery with ignition off and on, guess I don't understand the reading you ask

cruise98

The blue wire has no continuity. This is the problem.

Tom M'Guinn

Sorry, I was asking how much current is being drawn from the battery -- you do this test by connecting the multimeter in series and seeing how much current (in amp or mA) are passing through. I was just thinking maybe there is some large drain, but based on your last note, it sound more like you are not charging for whatever reason. I looked at the back of any old alt, and presume the noise reducer is the black one-wire component? My rebuild bosch came with its own new one...

Spidey944

This is along the lines I was thinking of. You only have 2 wires (3 if u have the Iceshark/Rennbay H/L kit) in that area behind the alternator shroud. When you pressed on the duct shroud, you made contact with these two wires going to the alternator as the orientation of the connectors must have been too close. The RED(?) power/excitor wire coming straight off the battery may have cooked. Hence the Bzzzzt noise and puff of smoke.

I did read all of the posts, and they started to backtrack a lot and get my mind all jumbled up. There is a simple sollution to this. Keep your diagnosis within these two wires going to the alternator. My guess is still the one from the battery. You have an open circuit not allowing the current to complete it's path. HTH.

tconn

For a number of years I made my living diagnosing
electrical/electronic problems, while I haven't really studied the schematics in full, logically this is where the problem should be.

tconn

The black component on the rear of the alternator I have is a
capacitor for noise reduction.

After looking into this a bit more, I agree with cruise98.
The blue wire at the alternator should have 12v on it with the key on, if not this could be the problem.

David Floyd

1.6 v with the key on at the blue wire, grounded to the alternator case

This is with a new blue wire run to the firewall connector, where does the blue wire run from there.. to relay pin 87 ?

Bri Bro

That voltage (1.6V) agrees with what I measured, there is a light bulb in the path that drops most of the voltage. The bulb is the alt warning light. Sure is a strange problem.

tconn

Some tests that I would try if possible.

Remove batt cable from back of alternator. attach meter to
alternator. Start car and see what the alternator is putting out. If it is generating voltage then re-connect the batt line.
Disconnect the alternator cable from the starter. Start the car, check voltage at the alt cable by starter. If voltage
normal re-connect alt cable to the starter and diconnect the power feed from starter to ABS module. Check voltage again. If voltage normal then could be a problem with the ABS module dragging the voltage down. your starter is working normally? so probably not a short in it.
This will isolate the cables as potential problems.

If you remove the batt cable from the back of the Alternator
and don't see it producing voltage, then attach a jumper cable from the negative batt post to the alternator case.
Check for voltage at the output of the alternator.
If its working, you have a bad ground.
If not working then I would disconnect the blue wire from the rear of the alternator, attach a 12v source to the alternator with it's negative on the case of the alternator.
Start the car and see if the alternator works. If it does then
you know the blue wire circuit is bad. If not then it's something with the alternator.

You can check the capacitor on the rear of the alternator,
Diconnect it, put your DVM across they usually fail open ,
if you see it "charging" then it is ok. If its a dead short then
it might be shorting the alternator.

Hope some of this makes sence and helps.
If not ............

David Floyd

Thanks for all the help guys, tomorrow after work I will be back under the hood following all above suggestions.

No ABS

David Floyd

Check 1) with everything connected normally, the large + at the alternator reads 20.3v grounded to the case.... good correct ? car running

Check 2) With the neg cable disconnected from battery there is continuity from the neg battery post and the blue wire at the alternator.....