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Unread 05-23-2003, 02:09 AM   #1
Popol
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alternator cj7 1979 fault & road lamps

Hi all,

I started a new thread as this is a new issue and i guessed if i posted in the other thread it might get missed.

I mentioned previously that the battery needed charging every night as during the day it was going flat.

I was all set to go and buy a new battery this morning, as the car had been idle for 6 months and suspicion was that the battery was probably on its way out,

However, Last night whilst driving I noticed something strange. the voltmeter which started at 12volts started dropping rapaidly until when I pulled up in front of my house it was reading around 7 or 8 volts.

Now I am no genius at cars but I am thinking, "Well, how can the alternator suddenly pump out less volts?" then it struck me that the voltmeter lights up even when the motor isn't running, so what it is actually showing me isnt the voltage coming off the alternator, but the voltage on the system, it also struck me as odd that when i pressed the gas pedal the voltmeter didnt rise or fall but stayed constant.

So this morning, with these nagging problems in my head, I decided to stop at the jeep garage before i went to buy a battery and order a thermostat and whilst there I asked if there was an easy way to test if the alternator was working.

They said, drop a voltmeter on the battery terminals, make a note of the output (in my case it was 12.4 volts, it had been on charge all night) and then start the motor and take a reading again, the voltage should be around 14 volts (mine read 11.5 volts).

So running the engine is actually draining the engine by -1 volt almost, whereas it should be +1 or +2 volts.

I switched the engine off reread the reading (now 12.2 volts) and restarted the engine to be sure (now 11.4 volts +-).

So pretty conclusive that the alternator isnt doing its job.

My question now is, before I replace the alternator is there a way to test the voltage actually coming out of it, I am hoping there may be a wiring fault somewhere that can be fixed with a little elbow grease and some patience, but before I do that I need to know that the alternator itself is actually giving out current.

Anyone know which terminal it is I should drop the voltmeter onto on the alternator and what expected voltage range will be coming off it?

Lastly, seperate problem, Road lamps, on the CJ there are two headlights, the main circular ones and the smaller round ones underneath, the smaller ones arent actually wired in I noticed, I also noticed that the bigger headlamps have been converted to dual filament, I noticed because it was night and a small blue light came on near the 80kmph mark on the speedo, and I thought, hmm, that looks like a full beam light to me, and indeed I was dazzling everyone as i drove, could i find the switch to turn it off, no chance, I drove along for half a mile, went over a pothole and the full beam turned themselves off, I think I have a long weekend looking at wiring diagrams ahead

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Unread 05-23-2003, 05:47 AM   #2
Popol
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well i think I found a way to test the alternator.

http://rollingmotors.com/charging.html

its not precise, but good enough for what I am looking for, at least to see if any voltage is coming off it, and where I need to start looking..
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Unread 05-23-2003, 10:00 AM   #3
knifeboy2
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Putting the voltmeter on the battery terminals is testing the alternator directly. If you were paranoid that it wasn't correct however, there is a screw post on the side of the alternator which you can use to test. There should be a heavy guage wire going to it with a rubber boot over it. Move the boot and do your testing, just watch where your hands are compared to the impellers and belts.

I would say pull your alternator, its really not that hard, take it to autozone and have them test it. They'll do it for free and if its bad buy a new one.

And with your voltmeter, it should go up and down depending on engine speed. The range should always be between 12 and 14 volts. Usually 14 when the engine is running and 12 when its not. If you're getting anything below 12 you're gonna have problems.
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Unread 05-23-2003, 01:06 PM   #4
Lightningdon
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headlights

Popol,
The high beam switch should be a foot operated switch on the floor. Look near the left side under the p brake pedal. Just step on this switch while driving to switch between high and low beams. The blue light on your speedo indicates high beams on.

Newer Jeeps use a push/pull action on the turn signal lever to accomplish this.
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Unread 05-23-2003, 01:19 PM   #5
rustyCJ
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you dont even have to remove the alt from the vehicle for autozone to test it now. they will wheel this lil cart out with all the stuff on it and test it in the vehicle.

i stepped on my highbeam switch one night to turn them on and the switch was rusted so bad no matter how hard i stomped on it i couldnt get the highbeams off. if sitting in the jeep the switch is to the left of the left foot against the body under the dash. if your highbeams are going on and off by themselves it sounds like you have a loose wire or faulty switch
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Unread 05-24-2003, 02:00 AM   #6
Popol
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Thanks for the tips guys, I dont know who autozone are, but if they ever set-up a shop in ibiza I will be glad to pay them a visit

I went to my local jeep garage, so far unable to buy (even though all components show on their schematics) :-
Water pump, Exhaust (any part), thermostat, thermostat gasket..

I don't have the luxury of well equiped shops or knowledgebale staff come to that, so I am pretty much restricted to doing everything for myself, hence the reason i asked for help.

Thanks for these wonderful tips though guys, switch on the floor for hi/lo beam really? wow, guess ill be on my hands and knees later taking a peek at that.

Thanks all, great response., thank you..
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Unread 05-25-2003, 09:31 PM   #7
Lightningdon
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Popol,
You can't miss the floor mount dimmer switch. It is pretty obvious once you look. I guess I never realized people didn't know about the floor dimmer. Us older guys remember when all cars had them.
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'75 CJ5 304cid, t18 tranny w/granny low, model 20 T Case, DANA 44 rear, 30 front, 4" suspension lift, 33" tires, in need of more work!

"The only thing necessary for the triumph of evil, is for good men to do nothing." (Edmund Burke)
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