Need help on 94 ranger either short or bad alternator or something else

[dean94]

Hello my name is Dean I was driving to work in my 94 ranger 2.3l 5 speed when it died acted like timing belt backfiring and no power then died coasted to exit ramp on side of it. Checked timing still in time changed crank sensor twice. Would only attempt to run for a second or just backfire. Read on here that alternator could be problem had alternator tested after being rebuilt 2 months ago tested bad had rebuilt still no luck had alternator checked and tested bad. Got completely different alternator from jerrys rebuilder that tested good from oriellys. Only time truck will run is when alternator is off truck unhooked or no power to alternator. Even changed fender solenoid due to father in laws advice still no dice tried 2 different battery's still no luck. Checked fuseable link on wire from fender solenoid to alternator and it's good. Left wire off at solenoid truck runs good decided to check and see if voltage was going through the main alternator wire had it had almost 42 volts on that wire.truck runs strong and solid with alternator unhooked just backfires when alternator is hooked only code I have on truck is a engine coolant temp sensor code

 

[franklin2]

Check the yellow/white wire at the small alternator plug, engine off, key off. You should have battery voltage there. Use the alternator case as your ground for your meter.

This wire is what the regulator uses to monitor the voltage of the truck, and with that information it throttles the alternator output. Sounds like this wire is not working correctly, and the alternator is going wild. 42 volts is too high. With it plugged up, you should get 14.5 when charging. Be careful, you could burn some expensive stuff up with a high voltage, though the battery will try to hold it down as good as it can. But it will start smoking and boiling also if it would actually run.

 

[franklin2]

P.S. I just looked at the diagram a little closer, that yellow/white is fused. Make sure that fuse is good.

 

[dean94]

What fuse number and also with alternator unhooked and trying another car as battery charger while it runs it just dies so anything above battery power makes it die

 

[dean94]

All fuses checked good

 

[franklin2]

Do you have a meter? With everything off, check that you have voltage on the yellow/white at the alternator plug.

 

[dean94]

I have about 12.8 on yellow white wire plugged in and unplugged with key off even had alternator tested again at oriellys while I ran some errands this morning and it tested good

 

[Mechrick]

decided to check and see if voltage was going through the main alternator wire had it had almost 42 volts

Check the condition of the B+ wire (the fat one) going to the battery. The only way you would see that high of voltage is if there is no continuity between the alternator output and the battery. Even a full fielded alternator would be unlikely to show that unless the battery was junk...

 

[dean94]

Battery in truck did test bad so I have been doing test with good battery from wife's crv that's less than 2 years old still got 40 volt I tested resistance on main battery wire and it had no resistance I haven't seen any bad spots on wire. Could guage cluster be bad causing this? Truck has 232,000 miles on it every ground has tested good that I've seen and read about on truck. One of previous owners of truck had done some crazy wiring on inside of cab for external wiring and a small soundsystem that was removed when I bought it I don't know what wires he may have tapped into

 

[Mechrick]

The alternator outputs on the fat wire, but regulates the voltage looking at the yellow/white wire. The battery is the buffer in the system, if there isn't a solid connection of the B+ wire to the battery or a solid connection between the negative post of the battery and the alternator case, what will happen is the regulator, looking at the y/w wire and seeing low voltage, will keep raising the output voltage on the B+ terminal. This is the only situation that can cause such high voltage on the output...

 

[dean94]

What do I need to check to make sure all that is in proper working order if I hook up fused battery wire to terminal on fender solenoid truck won't run with good battery from wife's car if I remove that wire or 3 wired plug from alternator I can get truck to run but no charging when I have 3 wired plug disconnected. If I have the fused battery wire removed I get high voltage through that wire while truck is running

 

[franklin2]

With everything hooked up normally, check again on the back of the alternator. With nothing on, nothing running, what voltage to do you get from the alternator case to the large output terminal on back of the alternator? The yellow/white wire seems good. But check voltage at that large output terminal with the nut on it.

 

[dean94]

With key off everything hooked up as it should be at that stud I had 12.69 for voltage and 12.69 at battery before I tested stud

 

[franklin2]

You definitely have a puzzler there.

 

[SenorNoob]

Isn't 42v about what a DMM shows when you connect to 12vDC with the meter set for AC?