99 Freightliner FLD120 VIN 940979 60 series Detroit We were sitting in line to unload at the mill and the truck gave a sudden "start/jump" and we lost power to the gauges and a/c fan. Still have dome light and cig lighter plug operational. It will still crank and run if you kill it. We have checked the key switch and have fire to all connections with it on, I have checked inside the fuse/breaker panel and haven't found a bad relay yet. In the breakers on the right hand side of the panel, there are 5 in a row at the top. All of the breakers were hot EXCEPT the first one. The wires that I could identify that were attached to it were 14, 912 and 279(unsure of this one). 14 runs down to a relay at the bottom of the panel. At this time, that is the only thing I have identified that MIGHT be the issue. Am I in the ballpark or should I be focusing elsewhere? Appreciate any help with this. It's hot w/o a/c in Louisiana!
It's probably related to the blower motor under the hood on the passenger firewall or the resistor block that controls the fans speeds. It should be close to the blower motor if you follow the wiring. You could unplug them and see if your dash gauges return. The blower motor relay is probably under the hood and is fused or a breaker.
