Come on guys, somebody out there ought to have some answers for this old boiler rat. I've only had one reply to my last post!!!

 

This may or may not help:

https://www.dieseltruckresource.com/...5&pagenumber=1

or this one:

https://www.dieseltruckresource.com/...=36421#newpost


This post no longer would link so here is the info:
Tip for speedo and charging problems...
« on: Today at 01:27:29am »

--------------------------------------------------------------------------------
"I thought to put this thread in because of the implications of several systems. In another thread speedo problems have been discussed and I have never seen this cause mentioned.

I was on the road and noticed that my speedo was not steady. Then it went to going wild. Sometimes it would be up at 100 mph and then down to 30. I stopped and did the side of the road thing, pulled the sensor and cleaned it, checked all the wiring. Checked for codes, none. Went back to driving and closely checking what was going on it did the following. When I would give it throttle it would go way up in mph. When cruising it would settle back down to more realistic figures. It also affected the odometer. I worried over this thing for a few hours of driving and then it quit charging.

Of interest, because who gets a chance to check this out…. Trying to reach the next truck stop the following observations were made. The first sign of problems was the speedo going crazy. At around 11 volts the chime and check gages came on. Ran that way for a long time. At the end of the safe low line on the gage the pyro dropped out. A little lower and the gages reduced in readings. The gage bottomed out and everything except the engine shut down. The FASS fuel system never quit. After a little bit the engine started bucking and it was time to stop. Pulling on the shoulder it quit, the battery was dead. I could see the truck stop….

After a nice lady let me hook jumpers to her car and charge it a bit, I got the battery charged. Got it to the Auction and picked up the load. Delivered by switching my battery with the battery in a Lincoln, which stayed running to charge the batteries. While running with no charging system the speedo was still crazy. Tach stayed good until it all quit. At one of my stops I pulled the field coil plug from the alternator. Problem over speedo solid as a rock, truck ran better more power back to normal.

So what is the point you ask…? With a leaky diode in the alternator, the AC will feed into the PCM and ECM and create havoc. My truck was charging and running with the AC getting into the system, poor filtering. I wonder how many hard to trace problems can be attributed to a leaky diode in the charging system? In the future I will be checking for AC on the charge line. If the speedo is acting up the first thing to check is for AC on the battery system.

Last but not least, that Optima tiny little battery is a great battery. Lasted twice as long as the Lincoln battery."

Originally posted by: Haulin in Dixie
Senior Member
Member #:209

Branchville, Alabama



"One Nation Under God" and don't forget it!



Another post that might be helpful:

http://www.turbodieselregister.com/f...4&page=1&pp=15


Hopefully, some of that helps, Kevin

 

I had the same irratic speedo problem on mine. It was all over the place, even regestering 90 mph while stopped and clocking miles. (got 40 mpg once) To make a long story short, I found a loose ground on the alt field block. The voltage spikes create a lot of gremlins in your electronics. Sometimes pretty time consuming to locate. Good luck

Howard