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It was a great day for a parade and a great parade it was. Bravo to the folks who put it on and participated. We had fun and it was nice seeing our steel soldier friends and meeting new one ones. This thread is worthless without

I meant 568, sorry for any confusion

Wire 568 to the alternator is a voltage reference which tells it to excite based on voltage. I'm guessing you're correct that turning off the battery drops this reference and the alternator goes full bore while winding down.

Is this an A1? Which alternator?

My guess is that when the battery switch is turned off while the engine is rotating the PCB circuit draws high voltage from the alternator because the ballast effect of the batteries is taken away and perhaps deactivation of the voltage regulator. That is my guess as to why the voltage guage...

From what I undetstand the PCB disables the starter solenoid based on a signal from the alternator. A missing alternator signal or disconnection may cause this. Check for voltage on wire 566 PIN F on the PCB when running. Not sure if it's AC or DC. No experience but folks have told me to...

I installed a 27SI self exciting alternator. The local shop I got it from had an old pulley of the same diameter. I may switch to a slightly smaller diameter pulley because the alternator doesn't excite until about 100rpm above idle. A 7/16 x 3" bolt and 1" spacer with a flat washer on each...

Sometimes after pulling the stop cable the lever that it actuates which cuts off the fuel supply sticks in the closed position. Pushing the cable does not reset the lever position. I had to open the hood and push the lever back by hand. Mine's an A1 NHC250 and it's on the drivers side forward...

PIN D goes to an over temp sensor that is seperate from the temp gauge circuit. I believe the over temp sensor is located on the top side of the motor near the surge tank. It can be identified by one of the two wires showing 36 on the tag. This wire goes to PIN D, and the other wire is a...

This post is a reminder for myself to rule out the engine over temp sensor connected to PIN D, which was eliminated in most trucks, when you are able to get back at it.

No problem. No buzzer or lights sounds like no power on PIN A or no ground on PIN H. Those are what give the failsafe box it's power. If you would like to speak on the phone when you are ready to troubleshoot again send me a PM. Does the buzzer still sound when the air low and parking brake...

This sounds like correct functionality. When air is good and parking brake is released there is no buzzer or lamps. Correct? When you disconnect the PIN A wire you are removing power to the failsafe box which kills the buzzer as well as all other functions. This is correct functionality.

It's possible that more than just the failsafe module was bad. When the ignition switch is turned on power is applied to the failsafe box. That is part of the reason the buzzer starts when the ignition is turned on. The buzzer should stay on until the air pressure is good and the parking...

The most common regulator on circuit boards is the 7805 variety. They are a three leaded transistor looking device and should measure 5VDC on the GND(usually center pin) to OUT pin. The reading from GND to the other pin should be 5V or (usually) higher. http://lmgtfy.com/?q=7805+regulator

Many circuit boards with digital logic, which is usually what CMOS refers to, use 3 or 5VDC to power the ICs (microchips). The power either comes from an external power supply in the correct voltage, or a higher voltage is reduced and cleaned up in an onboard regulator circuit. As a previous...

:not worthy: :not worthy: :not worthy:

I was doing some work at a proving ground for a tier one rear differential, among other things, supplier and witnessed some testing. They were steady jamming a truck back and forth between forward and reverse giving it h*** until it finally broke. When the tire smoke cleared they drug it into...

When new model vehicles are in the design phases there are mocked up tests that occur along tbe way. Final alpha, beta, and preproduction tooling tests are standard procedure as well. Real world testing of samples at each stage using real world driving conditions and controlled conditions...

I believe this method also speeds up the process of "splitting" the cases!

No luck getting my alternator rebuilt at the local shop. After looking at it scratching his head for a few minutes he recommended I replace it with a 27SI and offered to sell me a clone(WAI) for $165.