Blue alt/voltage reg wire not getting power until I rev.

Post by **Sluggo** » Thu Apr 11, 2013 1:23 pm

Unusual issue. I use the blue wire coming from the voltage regulator as a switch for my fuel pump and auxiliary battery relays. I've noticed lately that the battery light stays on and the blue wire doesn't provide power to the relays until I rev the engine up to about 3000 RPM. I now have a new alternator, regulator and harness but the issue still persists.

Post by **Amskeptic** » Fri Apr 12, 2013 7:16 am

Sluggo wrote:Unusual issue. I use the blue wire coming from the voltage regulator as a switch for my fuel pump and auxiliary battery relays. I've noticed lately that the battery light stays on and the blue wire doesn't provide power to the relays until I rev the engine up to about 3000 RPM. I now have a new alternator, regulator and harness but the issue still persists.

That is classic blown diode behavior. Diodes can blow fast and silently. When you *first* replaced the alternator, did this behavior go away . . . then come back?
ColinSiteSeemsCreakyBalkySlow

Post by **Sluggo** » Fri Apr 12, 2013 10:03 am

Behavior did not go away. I've used the tester several times at 2 different AutoZones and the diodes always passed.

Odd thing is my starter passes then fails then passes then fails. Starter draws between 65 and 89 amps. Different every time I check.

I should add (embarrassingly) that my tranny ground strap has been missing since I owned the bus. Never noticed. Replaced it a few weeks ago. Charging is much better now and a few gremlins went away but this blue wire issue still persists.

RSorak 71Westy · Post by **RSorak 71Westy** » Sun Apr 14, 2013 9:35 am

The diodes always pass on the main output post, there are seperate diodes under the post the blue wire coneects to and one of these ARE bad. If they tested the blue wire terminal like an output term they would see this.

Post by **Amskeptic** » Mon Apr 15, 2013 11:29 am

RSorak 71Westy wrote:The diodes always pass on the main output post, there are seperate diodes under the post the blue wire coneects to and one of these ARE bad. If they tested the blue wire terminal like an output term they would see this.

. . . this man knows, Sluggo. He has been baptized by the fire.
Colin

Post by **Sluggo** » Tue Apr 16, 2013 10:31 am

Guess I'll look into a 70 amp alt since I'm pulling it out again. Thanks for the info. Is it okay to drive around like this for a while? Once I rev all is good and I get full charge.

Post by **Amskeptic** » Tue Apr 16, 2013 1:03 pm

Sluggo wrote:Guess I'll look into a 70 amp alt since I'm pulling it out again. Thanks for the info. Is it okay to drive around like this for a while? Once I rev all is good and I get full charge.

Yes. I lived with blown diodes for years. Had to disconnect the (-) cable if the car sat for any time, because it was slowly bleeding to ground. Lousy charging ability, but I was always at 65-70 mph on the road, where it charged plenty enough.
Colin

RSorak 71Westy · Post by **RSorak 71Westy** » Tue Apr 16, 2013 4:20 pm

Is it okay to drive around like this for a while?

Absolutely the main output terminal is working fine. The blue wire terminal is just for the charge light. If you dont mind it glowing at you all the time your good to go.

Post by **Sluggo** » Wed Apr 17, 2013 6:10 pm

Cool! Thanks!

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Blue alt/voltage reg wire not getting power until I rev.

Blue alt/voltage reg wire not getting power until I rev.

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Re: Blue alt/voltage reg wire not getting power until I rev.

Re: Blue alt/voltage reg wire not getting power until I rev.

Re: Blue alt/voltage reg wire not getting power until I rev.

Re: Blue alt/voltage reg wire not getting power until I rev.

Re: Blue alt/voltage reg wire not getting power until I rev.

Re: Blue alt/voltage reg wire not getting power until I rev.