Blower fan not running on Isuzu trooper?

First of all check the fuse in the fuse box.The fuse located under the dash.


In the dash fuse box the fuse should be marked " BLOWER MTR" a 25 amp fuse.
Also test the fuse and check if you have 12 volts on both sides of the fuse. In some cases you realize fuse may be good but still need to know if power is going to that fuse and through that fuse.If exact power voltage is not showing,then fuse is near to weak and has to be replaced.

Check the large fuse under the hood FL-1 "MAIN" shown in diagram. It is a lrage 80 amp fuse and we need to know if there is power to and from it or if it is blown.

Also if fuse checked out ok,then it can be faulty relay.

In the dash, there is a heater/Ac relay. Turn key on , pull the relay out and probe the terminals and test for voltage to the relay.

See the diagram below for better understanding:-----

For location of this under hood fuse box,see the diagram shown below :-----

 

If you can get power to the fan, there are a couple different items that control it, turn it on etc,. Power is always to motor, it is the ground side that controls it. maybe you can work with diagram. There is a special module for fan speed . It could be bad as well as the control head. The problem is on High, that module is bypassed and goes through another relay.

See the detailed diagram shown below:-----

This details will help you.

Thanks.

See below latest solved car problems :-----

How to Remove Blend Door Actuator on 2008 Honda Odyssey?

http://howtobyme.blogspot.com/2011/12/how-to-remove-blend-door-actuator-on.html

How to Remove Passenger Side Blend Door Actuator on 2008 Honda Odyssey?

http://howtobyme.blogspot.com/2011/12/how-to-remove-passenger-side-blend-door.html

How to Remove Driver side Blend Door Actuator on 2008 Honda Odyssey?

http://howtobyme.blogspot.com/2011/12/how-to-remove-driver-side-blend-door.html

How to Replace Engine cooling Fan on Audi A4?

http://repairhelpcenter.blogspot.com/2011/11/how-to-replace-engine-cooling-fan-on.html

Replace Fan Relay but still Radiator cooling fans not working?

http://schematicsdiagram.blogspot.com/2011/12/replace-fan-relay-but-still-radiator.html

DIC says "COOLING FAN FAULT"?

http://schematicsdiagram.blogspot.com/2011/12/dic-says-cooling-fan-fault.html

Heater fan and headlights will not turn off with ignition off?

http://technoanswers.blogspot.com/2012/01/heater-fan-and-headlights-will-not-turn.html

Fuel pump relay and cooling fan relay troubleshooting on 1997 ford thunderbird?

http://repairhelpcenter.blogspot.com/2011/10/fuel-pump-relay-and-cooling-fan-relay.html

Where Is Radiator Fan relay and Fuse Located on 2004 GMC Envoy?

http://schematicsdiagram.blogspot.com/2011/12/where-is-radiator-fan-relay-and-fuse.html