front and rear brake pressure gauge shows diffrent pressures

[Plasa]

Hello all!
I have a strange problem with the air brake pressure gauges. Pressure is about 120psi on all 3 tanks, CTIS is working well, but the 2 pressure gauges shows front brake 90 psi, and rear brake 120 psi. Does anyone had a same situation? The 2 pressure transducer are near the left front wheel, behind the bumper right?
Maybe it's a transducer problem, or wiring?

Christian

 

[Suprman]

The transducers are under the drivers dash. I have seen their contacts rub on part if the dash. Sometimes the housings loose their ground. Could be the gage though.

 

[Ronmar]

Yep, under dash. You should be able to swap gauge signal lines between sensors to determine wether it is a gauge issue or a sensor issue. Since they vary resistance of a pathway to ground, make sure the connections from the sensor to ground are good. A bad ground could cause a gauge to read low...

the sensors also provide a contact closure to activate the brake idiot lights on the panel, so don't mix up the wires... They are shown on the schematic at F 177.

 

[Suprman]

I see so many trucks with odd gauge issues most related to ground issues. The senders are grounded thru a bolt going to a dash bracket. I see alot of them intentionally unbolted the low air buzzer will come on in error with the housing grounded.