KW water temp & oil temp guages not working

moisture in one of the ecm plugs? shut everything off, pull each plug apart and spray with wd-40? once its working put some Di-electric grease on each plug

 

They also make a electric spray cleaner for sensors that are safe to use. I think it's a lot like brake cleaner. You can find it at any auto parts store. I know I used that on my personal car back in the day. Then once you put everything back together apply some de-electric grease to everything.

Good luck.

 

As with every electronic problem start with the basics, clean the battery terminals. ground straps. If you have a Multimeter at 1200 RPM lights on, AC on high and fan on high Check the right front corner of the motor to the frame for voltage drop, check the cab to frame, the frame to battery ground, and the cylinder head ground stud to frame. Most problems are from stray voltage.
Adding a ground cable from the right front corner of the motor to the frame will cure a lot of problems. Cleaning connections, and adding a little dielectric grease will save you a lot of problems. It is something you can do while waiting anywhere.
Disconnecting the batteries and with a regulated charger, independently charging them is also a very good idea to do. Then test the voltage after they sit for a day disconnected.
I have seen a truck come in with a long list of repair bills, and codes. And a customer just furious when he is told the connections were dirty. He had paid me $105 dollars to wash his batteries and truck, and clean connections and make up a 3 ft ground cable, and mount it from the water pump mount bolt threw the front cover to the frame. Clear the codes and go for a 1/2 hour drive.
Not one thing that he could not have done himself, with a wire brush, some emery cloth, a tube of dielectric grease, some basic hand tools, and $5 dollars at the car wash.

 

Sometimes Mr. JohnP3 I think your a brainwashed Detroit/N14 FLD lovin nut. Then sometimes you have really good advice.... like now. I could not agree more. Thanks for posting your thoughts please keep it up.

PS We'll take the good with bad

 

Where is the sending unit located for the water temp gauge on a C-15? My gauge has started bouncing around like a wire is loose.

 

I have the same problem with my water temp gauge!!! Mine started acting up when I had problems with a plug that goes through the firewall to the ecm,,,truck would loose power when it hit a bump,,,ended up being a wire in the inside of the firewall plug,,,after wrestling around with that plug,,,my water reading are always off,,,if I throttle up,,,the gauge goes down!!!
Could be the same plug,,,on my W900 (2000),,its the plug that about dead center of the firewall,,,thinks theres something like 60 pins in that plug,,,best to get a diagram from the KW guys!!!