Diagnosing AC/Heat/Blower

[JustJohn]

Could use some help on trouble shooting a non-functioning blower. I've run through the service manual checks and it appears to be telling me it's the switch. Is it a common failure item?

Also, is there anywhere I can safely put in a jumper to check blower operation? I have a live power feed wire but everything else is reading dead all the way back to the switch.

 

[75gmck25]

Does your truck have A/C? There are minor variations in the wiring for A/C vs. non A/C trucks.

In most cases the high speed for the blower is a separate direct connection that is activated by the blower relay, and the lower speeds run through the resistor pack. The high speed relay is on the plenum under the hood on an A/C truck, and usually has an inline fuse running over to the power point near the brake master cylinder. The resistors are also mounted on the plenum under the hood.

Bruce

 

[JustJohn]

it's an AC truck. Power to the relay on the plenum. Everything from there back checks dead on my meter.