Fan not coming on in heat mode

[jasonjuu]

Hi,

I have a 94 Sonoma, 2.2L, 5 speed, no AC or power options. The fan is not coming on on the heat mode but works on all other modes. The fan speed control wasn't working so I replaced it.

Any idea what could be causing this? Is it the control switch not working? Or a lose of vacuum on one of the lines?

Thanks,

Also there are 4 vacuum lines on the back of the switch, two black, one blue and one grey. and two ports that have nothing attached.

 

[ferretx9]

Sounds ( to me ) like something in the switch is bad -
the fan itself does work and there is power at the switch
itself ( it works in some modes ) , probably has a bad / worn
contact inside it.