90 K1500 speedometer stuck at 30 and no odometer after theft!

[clint5191]

I have a 90 K1500 with the speedometer stuck at 30 and no odometer after it was stolen by breaking the steering column cover and exposing the rod to the ignition switch! Also the truck has less power and throws a code 24 on highway ive already replaced the speed sensor but can’t think what else it could be other than maybe wiring or the ignition switch any help would be appreciated!

 

[DerekTheGreat]

Might not be your issue, but check the fuse panel. I had a 1988 C3500 which didn't have a working speedometer- turns out the socket to the fuse which supplies power to the VSS was corroded.

 

[clint5191]

Ok thanks I’ll give that a try tomorrow I also have an issue with my defrost turning on at random times and with the display not working there’s no way to turn it off so might all be a wiring issue! Any other info would be appreciated!

 

[DerekTheGreat]

Yah, use a volt meter and check continuity across all the fuses. Inspect further if any fail. I was surprised by the '88, as the truck was very clean rust wise- only a few bubbles in the cab corners. Power supply to the HVAC panel might be intermittent or a bad ground. When it does turn on, can you not turn it off by the button? I'm lazy, so the first thing I'd probably try out is another HVAC head unit. I think you can swap one in from '88 up to '91. After that, they changed the voltages going to the servo motors for the blend doors and such. Basically, if it's got a "MAX A/C" button, it isn't going to work with your truck. Least not for long.

 

[clint5191]

Ok I’ll try that tomorrow and it randomly turns on by itself and works while driving either defrost or floor vents on high with no display and very rarely the display works and it operates correctly