Suburban Heater Problem!!

I have a 1998 GMC Suburban, with a major heater malfunction. The blower works every now and then, and only on high. If you turn it off after you get it going, and then go to turn it on again, you get nothing...sometimes if you flip it back and forth it starts up again. The blower motor, resistor, relay and switch have been replaced....now what?!? Any help would be appreciated, because I'm about ready to just run a hot wire with a switch to it to get me through the winter.

Thanks!!!

Welcome to AF. I am going to transfer this the Sub. forum in the Chev. Group, better chance for responses.

Make sure the blower has a good solid ground.

The ground was one of the first things I checked. :)

Sounds like you've replaced everything that would cause this. So the next thing is to check the wiring and connections. The fan sw is powered by the "HTR-AC" Fuse #12 25A in the IP fuse block. I would replace that fuse just for "grins" to see what happens. That fuse is powered from a contact (one of five) in the ign sw in the "run" position. Need to check for 12v from the ign sw to that fuse while wiggling the ign sw and wiring to see if you're loosing the 12v.

The resistor pack is in the picture only in low, m1 & m2. On high the relay powers the fan from the "BLOWER" fuse #3 50a in the underhood fuse block but the relay gets the "energize" signal from the fan sw.

Hope this isn't too confusing and helps you along.

Stickman, nicely done!

Thanks Stickman, I will check that out tomorrow. I've already tried changing the fuse (25amp), but haven't tried wiggling the wiring running to it to see if I had a short. I was looking at the wiring diagram, do you think the A/C controller could be the issue? Is there any way to check that out, without buying a new one? It looks like it runs power to the resistor and the high and low blower relay.....

The blower motor, resistor, relay and switch have been replaced....now what?!?

Thanks!!!

This is from your 1st post. Notice I have "switch" highlighted. Did I wrongly assume that "switch" was not the HVAC control panel?? If so, that would be the likely culprit. Since you have a schematic take it out and check continuity from the power feed thru all the contact positions.

The switch I was referring to is the one located in the dash behind the knob. Where is the HVAC control panel located? I think I remember reading something about it being behind the kick panel on the passengers side? Thanks again for all your help!!

The switch I was referring to is the one located in the dash behind the knob. Where is the HVAC control panel located? I think I remember reading something about it being behind the kick panel on the passengers side? Thanks again for all your help!!

The HVAC control panel is the one in the dash!! The one with the "temp" control, the "floor, vent, defrost" control, the A/C push button and the "Fan" speed control. What switch behind the knob are you talking about??

The switch I replaced was the small black cylinder directly behind the knob you turn to turn on the fan....should I replace the whole board?