Speedometer problem

[MXTMOPR]

Testing sending unit

Connect meter to the two pins inside the plastic housing. Slowly turn the shaft, the multimeter will show an off and on, swing of the needle as you rotate the shaft. Make sure your meter is set to show continuity (meter pegs when both probes touch each other) If the meter swings from low to hi the sender is working properly.

 

[RWWinslow]

Ihave been thru my speedo system back to front several times. Also, check your electrical connections - they will need replaced as the unit ages.

 

[JGrefenstette]

Just bought my first cummins this weekend. on the 2 hour drive home stoped for fuel. when i pulle back out on the highway, the speedo was dead, along with the odometer. it was dead all day. i talked to a buddy who mentioned the speed sensor in the rear dif. i looked at that and then looked at the gear reducer in the transfer case, jiggled that a little, and it has worked fine since.

also, is there anyway to adjust the speedo for bigger tires, to compensate?

 

[Moab4x4]

Speed sensor in rear diff is for ABS only, no connection to speedo.



The only correction for larger tires, etc is to buy a customized ratio adapter to go between the VSS and the xfer case. There are a bunch of suppliers of custom ratio adapters out there. Many are online.

Ken

 

[Tumbler]

With A LOT of Luck

Sorry, long post here.



When I got the truck the odometer was out. A few months after I bought the truck the speedo became erratic, jumping all over the place, sometimes work, other times not. Finally it gave out.



I hoped that the odometer and speedometer problems weren't related and started with the obvious. I found that the odometer gears were cracked so swapped them out according the the following thread.



https://www.turbodieselregister.com/forums/1st-generation-ram-forum-1989-1993/142992-odometer-repair.html



Tested it and the odometer worked fine.



Noticed that the circuit board for the odometer and speedometer had what looked like burnt paths. I thought it was odd that the odometer would work on a board that got fried. Figured maybe the fried parts were isolated... Mysteryman's reference to circuit board repairs and swapping electrolytic capacitors inspired me to try working on the circuit board.



https://www.turbodieselregister.com/forums/1st-generation-ram-forum-1989-1993/153124-92-not-shifting-into-o-d-no-speedometer.html



I started with removing/scratching off the burnt paths. There were areas that looked like current arched. (I didn't realize that that much current could run to the board. Is it true that the board can get fried? ) After removing it I noticed that only one of the paths were totally gone. I got the idea to connect the broken link by soldering a thin insulated electrical wire. Tested it and the fix worked. I also found out from a friend after I reinstalled everything that instead of soldering a wire I could have used a circuit path pen that you can purchase from Radio Shack to redraw the path.



I consider it a temp fix and mainly did it because the first company I got a quote on for a used console (through junkyarddog.com) wouldn't ship to Hawaii... even at a higher rate. I was told that I could ship it to family or a friend in the mainland who could then ship it to me. :-laf Figured I had nothing to lose by tinkering with the unit. I was already used to both the odometer and speedometer not working. (Other quotes were slow in coming and I received them after I took care of both repairs... )



In retrospect I was extremely lucky to arrive at a fix. I feel like since I have no experience with these type of repairs I could have easily complicated the problem. I did look at and took apart the VSS. (BTW From tinkering with the VSS it looks like I'll eventually have to take care of a rounded square shaft... as covered in this thread. ) I was also ready to swap out capacitors as suggested in another thread before I started working with the circuit paths. As stated earlier I was even ready to purchase a new console, which I probably will still do to have it on hand just in case.



I'm left with a few questions though. Is it odd that none of the circuit board components were fried if there was a short in the board? Is it possible that what looked like burnt paths could have been corrosion? Some of the burnt areas looked like rust bubbling under paint.



Thought I'd share. Thanks to all who contributed to this thread and other threads I referenced. Hope it helps someone.