Electrical problem

[slam1]

I need some input. Batteries in my 88 250 are not charging. Replaced the starter,voltage regulator,exciter wires from alternator to voltage regulator, had the alternator and batteries tested twice. Put a VOM to the alt, only have 12.2 coming out. With the truck running I pulled all the fuses one by one to see if the gauge would fluctuate, it never did. I also checked all grounds. I'm baffled. You folks on this site have always been very helpfull to me, thank you all. Now if anyone has any input, I sure could use it.

 

[icanfixall]

Your alternator has crapped out. It should show at least 13 volts output.

 

[lotzagoodstuff]

+1 for shot alternator, should put out over 13 volts.

 

[suv7734]

Did you disconnect both battery grounds before you changed the regulator? Have you checked the ground connection to the regulator?

 

[MIDNIGHT RIDER]

Did you disconnect both battery grounds before you changed the regulator?

What would take place if a regulator was changed without removing the grounds ??


I replaced mine many years ago and didn't mess with any wires except those connected to the regulator itself.

Thanks.

 

[slam1]

I had the alternator checked not once but twice at a local parts store, under max load it put out 14.5 but on the truck it puts out 12.2 I dont get it!! No I did'nt disconnect the grounds, but I did check every other ground on the truck.

 

[BigRigTech]

Rotating speed might be an issue, if the test bench is spinning it faster than your idle speed it will put out more. Do some voltage drops across all your connections and see if you are loosing the voltage somewhere through a bad cable or etc. Are you reading two different charge rates at the alternator studs and the batteries?

 

[slam1]

I did a continuity test on all the wires I could. Voltage is the same out of alt. as at the batteries 12.2 no voltage drop, same charging rate.

 

[BigRigTech]

By voltage drop tests I don't mean continuity. Put a lead on either side of all your conections. If they are good the meter should read zero, if they are not good then it will show the voltage that is being "used up" by the resistance at that connection. What is the voltage reading at your exciter wire telling the alternator to put out?

 

[slam1]

I just went out and fired it up. Got no reading on one of the exciter wires and a 0.1 on the other.

 

[hahn_rossman]

It sounds to me like the regulator is the problem, not the alternator. If you disconnect the plug to the regulator and put an jumper across the plug connecting "F" and "A" you will cause the alternator to produce it's maximum voltage (duh... with the engine running ok). Don't leave this connected for more than a second or two! Have your volt meter attached to the batteries and see if you get more than 13 volts. It will probably be more like 17! This is why you don't want to leave the jumper in. It will damage the batteries, blow light bulbs and cause other mischief. If you get the voltage than the regulator is at fault. Replace the sucker and see if you can find a good quality replacement. I know the diesel rattle is ******* them. The budget regulators we're only good for a couple of weeks on my truck. When you unbolted them you could hear a capacitator rolling around loose in the housing!
I eventually found a really nice one from the local auto elctric rebuilders near my shop, it's adjustable! 14.7 volts keeps the batteries in top form!

here is a longer description of the alt/reg
http://books.google.com/books?id=3q...SSVI&sig=JdgrkGZxJeYVZMXsgW5yH9lGyOM#PPA89,M1