how do I test the electrical wires and switches in my 4 wheel drive, 1989 GMC...

[tahuya_eagle]

...sierra K2500 700R4? I bought a new actuator and installed it but the light on console when in 4L or 4H does not light up. bulbs are good.. I want to test the tranny and transfer case wires

 

[Molson02536]

...sierra K2500 700R4? I bought a new actuator and installed it but the light on console when in 4L or 4H does not light up. bulbs are good.. I want to test the tranny and transfer case wires

When you place the transfer case in 4wdm you should get 12 volts to your brown wire at your new actuator at the front axle. There is also a 4wd switch beside the actuator that indicates that the front is locked, inspect that for any signs of damage and repair if any.

The switch only indicates to the light on your console to light turn on and off.

Good luck and keep us posted.

 

[als_gmc_2000sierra]

When you place the transfer case in 4wdm you should get 12 volts to your brown wire at your new actuator at the front axle. There is also a 4wd switch beside the actuator that indicates that the front is locked, inspect that for any signs of damage and repair if any.

The switch only indicates to the light on your console to light turn on and off.

Good luck and keep us posted.

I bought a new actuator for my 2000 gmc sierra, after much research on line trying to match up my symptoms with what others had. The old 4 wheel drive actuator on front axle doesn't work nor does the new one, I'm getting power to the brown wire on the harness that connects to the actuator...the switch light is solid on 2 hi but only blinks on 4 high when I try to engage..NO 4W Service light on Dash is ever displayed and I can hear some clicking on transfer case where the encoder is...any thoughts..thanks in advance

 

[south]

How does the switch on the transfer case play into this system? Is there something mechanical that happens to this switch when the 4wd is engaged? If, the switch on the xfer case is supplying power to the acuator, I would like to bybass this switch with a toggle switch in the cab. There is a brown wire and a light blue wire going into the switch on the xfer case switch.

I just replaced the acuator on my 91 k2500, but the 4wd is still iffy, sometimes it engages, sometimes not...

Thanks