Anyone know of a known problem with the heater not blowing? Fan switch usually bad, relay bad anything?

 

Yeah check the relay, does it work on defrost/any other setting or just heat?

 

Doesnt work on any setting

 

Could possibly be a vacuum leak? does your cruise work? There are blower motor resistors that could be bad as well, but I think some fan speeds still work if that is your problem.

 

Ive never owned vehicle (and Ive owned close to 75 !) That a vaccum issue would cause the blower to not turn on. Is this Jeep specific stuff? Now Ive seen vaccum issues cause it to not switch from hot to cold or defrost to vents etc.. Because most have vaccum operated blend doors.

 

I've got a '93 Cherokee and my heat is out. I'm not sure if it's the blower or what but the heat kind of trickles out a little on defrost but that's about it. Its a hassle to get to the blower and resistor so I'd like to have an idea before i go ordering parts.

 

Eh I just searched this forum and people seemed to suggest it a lot. If there is no vacuum to switch your settings, maybe it is stuck off. There is a good chance I have no idea what im talking about right now, but we will pretend I do... (I have no idea if there is an off setting that ignores the blower speed) We shall wait for someone to chime in!

 

Youve checked the fuse?
Power at the blower?

 

As strange as that seems. It wouldnt surprise me really.

 

Now you done went and called me out! No havent checked anything. Been busy putting a lift on, researching shocks and looking for tires. This heater thing was going to be my next project. I was just trying to find a good starting point. Im actually going to check to see if there is power going into the blower motor speed resistor. If so, then Ill check to see if any is coming from there to the motor switch itself. Fuses are good though. I been checking fuses alot lately tracing down other electrical issues such as intermittent dash lights which turned out to be a faulty rheostat switch in the headlight switch. Im one of the few people that electrical circuits in a vehicle do not scare me.

 

Id just turn the key on, put the fan speed on high, and check for voltage at the blower plug.

 

Sounds like a vacuum issue to me. Blower won't do a dang thing without it. Depending on the year, you can start looking for unplugged lines behind the front bumper or at the firewall. Another place to look is on the setting switch itself (I believe 97+ all have lines going through it to actuators on the evaporator case).

 

Wow, that is just really interesting that a vacuum leak can cause the fan not to blow. Now Im intrigued to see how this entire HVAC system works.

 

I really doubt that.
If you lose vacuum it will blow out the defrost vents. You will still have blower.
Id say you dont have power to the blower for some reason.

 

Now see this is what I thought and have seen on EVERY other vehicle I have ever owned. Vacuum only operated the blend door actuators.