Yj heat blower not working.

[richgilbert81]

So I have a 1987 jeep wrangler YJ. Earlier this summer the heat stopped working one night on a cold ride home. After tearing the dash cluster apart and testing the switch panel I now know that is not my problem. So i turn to the blower it's self. As I start to poke around with the meter I do have 12 volts to the terminals on the front of the blower. As I poke and prod with my meter lead I realize that the little red plastic/fiberglass part that the terminals go through is brittle and falling apart. The metal is literally rusted through. I am a hvac tech so I kinda know electrical. From what I do know about 12 volt systems I do think this is prob some sort of a resistor for the speeds? My question is do I need this part for my heat to operate? Can it be by-passed? This is not a daily driver at all. I only take it out in the woods a few times a month and it is parked all winter. But living in the northeast I really do need heat at night to get me back home from the trails. I do not care if I have blower speeds any more as long as it can be turned on and off!! Any suggestions are greatly appreciated. Thanks for the help folks!!

 

[greg92jeepxj]

The part pictured is the blower motor resistor that determines blower motor speed . It provides resistance to reduce or increase voltage for low , medium or high speed blower speed. If you cannot find the replacement part for any reason ( generally inexpensive) you can bypass it.
Just find the HIGH speed wire ( orange/white ? ) from your dash control switch and verify that it is hot in high speed position but not in any other position and wire it to the connection to your blower motor directly. It is already fused at the fuse box so that will be safe . No other in line fuse should be necessary to work. As long as you can turn it on and off with the dash control , this will satisfy your need. Just would like to say though , if the part can be found for cheap , why not replace it ? I'm sure as a tech you can clean up any corroded connections easily as long as they are not too badly eaten up. I understand your concern for not wanting to get too involved in this repair but it should not be so big a deal. Bypassing is easy but replacement should be easier , rust and corrosion your only chore. Just a thought. I am a fan of trying to repair things to work the way they were intended to if at all possible unless the design is flawed from the start and improvising must precede to improve over the original design. Hope this helps . I have full faith that as a tech you will find this easy . Greg

 

[greg92jeepxj]

Found this part on the Rockauto site just to help with parts numbers. Hope you can find it locally to avoid shipping charges and fix it cheaply if your parts guy can get it without driving up the cost to order it.

 

[richgilbert81]

Well that was a big help actually. I did ohm it out and check voltages yesterday. There was voltage coming out on a different wire each time I switched the fan speed knob. So yes you were right there. I was going to just wire the high speed wire to my blower mtr it self and bypass the speeds but I couldn't find any wires going in to the blower mtr!? So to save a headache I am just picking up my new resistor this week. I looked in engine compartment and also under the hood. The wires must go to blower via the plastic surround under the passenger dash panel? All the wires go in to the main harness and very hard to trace out. So thank you for the advice and I will be just repairing this right and be done with it for another 28 years I hope!!

 

[greg92jeepxj]

Well that was a big help actually. I did ohm it out and check voltages yesterday. There was voltage coming out on a different wire each time I switched the fan speed knob. So yes you were right there. I was going to just wire the high speed wire to my blower mtr it self and bypass the speeds but I couldn't find any wires going in to the blower mtr!? So to save a headache I am just picking up my new resistor this week. I looked in engine compartment and also under the hood. The wires must go to blower via the plastic surround under the passenger dash panel? All the wires go in to the main harness and very hard to trace out. So thank you for the advice and I will be just repairing this right and be done with it for another 28 years I hope!!

Your quite welcome . Glad all will work out . I'm sure you'll find this an easy repair and laugh about it later and the part is inexpensive so I know you'll feel that replacing it is easier than bypassing. It will literally be plug and play , aside from cleaning connections. Almost all the wires go back to the blower motor switch on the dash control and I think just one wire goes directly to the blower motor under the hood. But like I said , aside from cleaning connections , your literally just plugging in the new part . Lots of luck but I know you'll be fine . Your experienced at this type of work , will be just another repair. Greg

 

[richgilbert81]

Well so much for that one!! I replaced resistor and plug. Try heat and still no blower!! So the fix continues on.... I have power to the resistor on all appropriate wires. So I would assume the blower control in the dash is working correctly. I am going to start tracing wires back to the blower and go from there. I know there is one terminal sticking out of my fire wall right next to the back of the blower mtr... But that's all that is there. There is no wire anywhere near it that could if fallen off so I'm not so sure there was ever anything hooked to that terminal. Is this my blower wire? I do not see any wires around the blower on outside of fire wall that might power the blower. So I will prob try and get all the plastic apart under passenger side of the inside of the firewall and see if there is anything as far as blower wiring inside of that plastic duct work. My heat has always worked in the past. Hmmm.... Of course it worked great all summer when it wasn't needed but now I need the heat at night it gives me issues... I am planning on looking through my chiltons book for some schematics or break downs of all this before I tear into it but I'm a little doubtful it will be to much help.

 

[greg92jeepxj]

The inserted photos are from my 1992 FSM since my 1945 to 1987 CHILTON manual does not have a wiring diagram. The two photos of the defroster and evaporator assemblies are identical in both the CHILTON and the FSM . 1984-86 heater/defroster and 1987 evaporator assembly. I have only the 1992 wiring diagram from the FSM to go by and am hoping since the assembly is the same as the 1987 , from what I can see , that the wiring is the same. Am hoping this helps .

 

[greg92jeepxj]

I found these diagrams in a Haynes Jeep Wrangler 1987 to 1992 . It shows the same photos as the CHILTON and my FSM as well. Not knowing the YJ as well as the XJ , it seems to me , that is if I am correct , that there is a separate blower motor for heat/defrost and a/c , one for each ? The last diagram seems to illustrate two separate motor feeds. The XJ only has one blower motor . I was a bit confused so I included all this in hopes it will help .

 

[1995jeepyj]

It took me 4 days to figure out my heat. I finally got it working tho. It was one simple wire from the battery that wasn't connected to the high and low switch and a blown fuse. It was a simple fix but took forever to figure it out.

 

[richgilbert81]

Was it a factory wire from the battery? Hmmm. I have done bunch if electrical work to mine over years and do have a bunch of power wires going to the battery for different stuff. But I dont think any of them were there from factory for the blower. To cold and too much snow right now to try