No Electrical..help

[eastmedia]

I was trying to track down a weak charging problem. I changed the grounds and seemed to have it fixed. Just after getting it back together I went to start it up and when I turned the key I heard a "zap" and now I have nothing. No lights, no guage power, no electrical anything.

The only thing that happens when I turn the key is my aftermarket temp guage pegs BACKWARDS. Ammeter & fuel guage don't move. Battery is still fine showing 14V.

Stock alternator, etc... Any help is appreciated

[shifty]

Fuses still good?

[eastmedia]

Fuses are all fine.

[TR]

In general:
Make sure the harness is not burnt and proper fusing is in place across the amp meter circuit.

Your issue:

Sounds like you grounded something that does not want to be and it fried. Look for anything that looks like it got hot. Hopefully the ignition switch did not cook.

Un-do everything you did, replace any blown fuses, and rehook one at a time until the problem comes back...That is the one with the issue.

Good luck! TR

[eastmedia]

I just checked it again and I notice that when I pull the light switch out, it also causes the temp guage (aftermarket) to peg negative. The lights don't come on, but does that mean that the power is still there just still shorted or something?

I read in the manual about the headlight having a relay. Could this cause the problem? Anyway to check the relay or bypass it?

How can I check the ignition? I am able to remove the plug. Anyone now how to jump the wires to operate it without the key? (also known as hotwiring?)

[TR]

You've got something grounded that shouldn't be...Either because something fried or a wrong connection...All the other items you describe sound to be symptoms of the same. Don't waste your time on witch hunts based on new findings. Go back, disconnect your recent work and see if the problem goes away. If so, touch each item to ground and see if you get a big spark, blown fuse or anything else odd...That will be your trouble maker...TR

[eastmedia]

Thanks TR.

Went backward and reconnected as it was and what do you know...It works!!

It still seems to be charging a little low. The ammeter starts off in the + area and in about 15 seconds slowly creeps to just below the middle line.

When I step on the brake pedal, it shoots to the + side again until I release the pedal.

To test the alternator I removed the + battery cable while the engine was running and it was fine until I turned on the headlights, then it died. Looks like the alternator is not making enough charge?

Ron

[TR]

You know what? The symptom you describe (starts + then trails to negative and jumps around when a small load is applied) is one I had on a 510 a long, long time ago. I think I traced it to the external voltage regulator. The alternator was charging, but the regulator was all over the place and not consistently charging the battery.

If it is drivable, you can always take it to Kragen for a charging system evaluation, although I prefer to bring those monkeys just the alternator...

[garth]

When I step on the brake pedal, it shoots to the + side again until I release the pedal.

To test the alternator I removed the + battery cable while the engine was running and it was fine until I turned on the headlights, then it died. Looks like the alternator is not making enough charge?

From your description it sounds like your alternator has an open diode. If this is the case it's capacity to charge will be reduced to approximately 50% and will require higher rpm to build voltage. You can confirm this with ohmeter by testing the six diodes in the alternator. They are accessible through the rear opening. The three diodes adjacent to the output terminal should conduct to the terminal, the opposite three should conduct to the case or ground. If you do have an open diode its an easy fix for a rebuilder. If the diodes are good check the regulator under load.

I hope this helps.

[TR]

Garth - That's great knowledge gained for all of us, thanks! TR

[Linda]

I am reviving this thread because I wanted to know how to do the last test mentioned...testing the alternator diodes.
Does anyone know how to do this?
Also Garth mentions "checking the regulator under load" . ?
Thanks,
Linda

[datsunrides]

Holy graveyard Batman!

Think of diodes as electrical check valves. Current should only be able to flow one way. With an ohmeter, you should see nothing going one way and infinity the other. The loaded test Garth is mentioning is probably done with a tester that has a carbon pile (old tech) or load cell. Basically, it induces a load onto the charging system to check the amperage output of the alternator.

Mark

[Linda]

Alright, so Mark, break that down for the electrically-challenged .
What steps do I take with my analog multimeter?

Linda

[ttyR2]

With your ohmmeter set to the 'ohm' scale, touch the positive lead to the terminal on one of the diodes, the black lead to the case of the alternator. You either will or won't get any resistance (should be infinite resistance in one direction). On each diode, test one way, then flip the leads. When you find a diode that is either zero resistance in both directions or has infinite resistance in both directions, you found a bad diode.

Just remember diodes act like a one-way checkvalve for electricity. Current flows one direction but not the other.

One thing I'm not sure of is if each diode needs to be disconnected (unsoldered) from the others to test properly. Anyone?

[dbrick]

One thing I'm not sure of is if each diode needs to be disconnected (unsoldered) from the others to test properly. Anyone?

Usually not, should be able to read them. Last bad set I saw were physically broken/blown up.

Linda, (and anyone else with an analog meter)...Watch Sears, they have an autoranging digital voltmeter that goes on sale for less than $25.00, great tool, comes with digital temp and is user friendly. On sale this week. analog is good for some things, digital is fast and easy to interpret.
http://www.craftsman.com/shc/s/p_10155_ ... rical+Shop