I replaced the switch with a brand new one . Just happen to have a new one laying around . Checked all the fused . That did not solve the problem . Under the hood , there is a large enclosure on the passender side fire wall . The A/C pipes go into it . That looks like the blower area to me . There is a 5 prong electrical plug that connects to the right side ( the side facing the steering wheel ) . I check the voltage to these connections , and different terminals have 12V depending on the position of the fan switch . However , when I put the fan on high and unplug this connection , the fan stays on ?? I figured this connection was controlling the fan , but I guess not ??? On the other side of this fan enclosure ( facing the antenna ) , there is a metal bracket holding a small metal box that looks like a relay . When I unplug that , the fan shuts off . So replacing that box would seem logical right ? Others have replaced that part wasted thier money because it did not fix the problem . So... what do I do now ? Any ideas anyone ?

Thanks .

 

sounds like the blower motor resistor is bad

 

I agree with your diagnosis.

 

Cool , sounds reasonable . So I how do I test that theory ?

 

the fact that the blower only works on high is test enough, when the resistors go bad they go into default mode. On chevy and ford I believe default is high, and dodge its low. Pull the motor resistor out and replace it. Should fix your problem

 

Right on buddy , thanks . I will do that .

 

Just some Im clear on this , here is the situation :

Heater fan settings low and medium do nothing . Hi setting runs on hi . Not all 3 settings make it run on hi . I attached pics of parts . You are saying that I need to replace the part with the twisted wires ( as pictured ) , and not the little metal box ( as pictured ) correct ?

When I unplug the thing with the twisted wires , the fan does not turn off . When I unplug the little metal box , then fan does turns off .

And if the thing with the twisted wires needs to be replaced , how in the &^$%& does that part go bad ? It looks like twisted wires , not a computer !

 

when you unplug the resistor (twisted wire thing), the fan doesn't turn off because it's already being bypassed because it's faulty.

 

STARMAN, what are you working on? Might help narrow down your issue a bit better. From the looks of it, you have an earlier 1st gen. Please always provide your vehicle details when requesting technical help. It assures that the information provided is specific to your vehicle.

With the older resistor packs, it is very easy to test continuity on all of the coils to make sure that it is operating properly.

Once you post your vehicle info, I'll dig up a wiring diagram for the blower motor controls and we'll get to the bottom of your problem.

 

Sorry , its a :

1992 Chevy S-10 Blazer 4x4
Automatic
A/C
4.3 Vortec
212,000