# 75 dasher alternator help



## young_olds (Oct 24, 2014)

alternator was bad on my 75 dasher, parts store showed a 65 amp about $10 cheaper than the 55 amp. but the 65a didnt have the plug the old one did, i figured no problem ill just cut it and make it work. well it seems like the alternator kicks on and off randomly and never really charges. I took it in to get tested and it tested good. I was reading service manual and it said that the alternator i have on now wasnt used until 77, looking at the wiring diagrams it appears it may be wired different. Im wondering if the 65a is actually wired different and if so can i wire it correctly or do i need to go back to a 55a. or is the my problem related to something else? any help is appreciated.


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## cuppie (May 4, 2005)

Can you post up pictures of the backside of both alternators?


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## young_olds (Oct 24, 2014)

i went from this

to this


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## young_olds (Oct 24, 2014)

I figured with the wires hooked up to the corresponding terminals it would would just fine. is there anything else that could cause this, it seams to be completely unrelated to rpm's.


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## young_olds (Oct 24, 2014)

Is there a relay or anything I should look at? Most of the time it acts like a low battery, I've had three different batteries in there with the same result. I did notice it sounds like a relay clicks corresponding with more power. If I have my heater, headlights and rad fan on they all run low but as you turn things off the remaning pick up. Unless the power kicks in then everything goes back to normal


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## cuppie (May 4, 2005)

The wiring scheme for both is the same - red wire(s) to B+, blue wire (exciter) to D+. 

First things first: 
Does the charge light work correctly? Key ON, engine not running; the light _must_ be illuminated. If it doesn't, the alternator may or may not start. 
It's OK if you have to blip the throttle a bit after startup to get it to go out - it's 'normal operating characteristics.'

Assuming that the above check out.... Voltage drop(s.) Unless you've replaced them, the battery cables on that car are 40(!) years old now. Time for new ones.  
To verify: Grab a DVOM (volt meter.) Engine running, measure the alternator voltage directly at the alternator (+ lead to "B+", - lead to the alternator case.) 
Repeat this measurement at the battery. Significant difference? Start measuring across the cables (say, meter + to alternator stud, meter - to starter (or B+ post.) The higher the voltage measurement, the greater the drop is (literally, you're measuring the losses across the cable.) 
Of course, you'll need the engine running to do this. And, voltage drop scales with load - the more loads (lights, blower, etc.) you have on, the more power you'll lose across a poor connection or cable.

A visual inspection isn't necessarily worthwhile here (unless the cable is so corroded that it looks like it's about to fall apart.) 
The DVOM, though, will tell you exactly what kind of condition the cables are in.


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## young_olds (Oct 24, 2014)

Idiot light functions as it's supposed to. I'll do the volt meter test and see what I get. Positive cable looks newer but the ground looks pretty old


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## krautwhlz (May 10, 2010)

young_olds said:


> Idiot light functions as it's supposed to. I'll do the volt meter test and see what I get. Positive cable looks newer but the ground looks pretty old


A new, separate ground lead to the alternator case really helped after swapping a later (90A Passat) alternator into my Dasher. Like the throttle blipping thing... I don't know why, but it worked/works & has never given any further trouble. Seems like all my VWs, sooner or later, have gotten additional ground leads... and functioned better thereafter. Weird!

J.R.
SoCal


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## young_olds (Oct 24, 2014)

At Idle voltage drop was maybe half a volt, I added a ground strap to the alternator and will probably replace my battery ground cable


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## young_olds (Oct 24, 2014)

Lastnight I could see an arc on my throttle return spring, it goes from the car to the fender. I figured that meant it was trying to ground out through the spring. Also noticed i couldn't find a ground strap from the engine to the body, my battery ground go straight to the engine. This morning I cleaned up all my ground contacts and added grounds to the body and so far it seems to have fixed my problem. On my drive home tonight I'll be able to test it with the headlights and fans in to see if it actually helped.


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