I have a 91 Cherokee and when I turn on my A/C it works great. Hi, Low everything is fine, EXCEPT, when I run the blower on Hi, I have noticed that the A/C heater blower speed selector switch gets hot, and also it will melt the 25 amp blower fuse down on the floor on the drivers side fuse block. I have changed the blower with a new motor, put in a new resistor pack, changed the A/C heater control panel and the blower switch and connector plug. and it still gets hot. maybe the new blower motor is pulling to much current, my question is, how much current is ok ? Less than 25 amps because the fuse is a 25amp fuse ? other than the blower motor maybe being bad, what else should I check and what could be causing the blower fuse to get so hot ? thanks guys and I hope to hear from some one soon. thanks in advance.

 

This is going to sound ridiculous, but does stuff get overheated and blow the fuse if you run it on heater mode?

 

Well I never checked it with the heater, here in Abu Dahbi it is seldom less than 80 degrees so I don't even have the heater hooked up. I did check it in vent mode, no A/C, and it does not get as hot as it does in the A/C position.
I have run the blower on high and the wires at the blower them self are NOT hot at all.,,,

 

Motor is bad... Too low of resistance in the windings. Works OK on the other speeds because the resistor pack protects the system. Replace the motor. Also check the wiring insulation as it sounds like you may have damaged things.

 

Today I went out and hooked up my multimeter to the hot side of the blower. In low it pulls only about 7 amps. On high it only pulls 11amps, this was all done in the vent position, and the blower fuse did not get hot at all. BUT when I tested it in cool with the ac compressor kicked in, the fan still pulled the same amount of current but the blower fuse got very hot real fast. So, any ideas ? I dont understand how the compressor is on the same curcuit as the blower. Any ideas ? And thanks in advance for taking the time to give your much needed assistance. I also noticed that the wires on the blower itself do NOT get hot or even warm...the heat starts at the off/max/norm slider switch. I can feel it when I put my finger on the top of the switch. the big plug that connects to the switch has 4 wires on it, the big blue one, I am assuming is the 12 volt sourse for the system, and when you put it in vent...the 12 volts go from that big blue wire to the purple and yellow wire that I believe goes to the blower,,,when you put it into an A/C position ( max, norm or bi level,) the 12 volts goes to the normal blower purple and yellow wire AND to the smaller green and black wire that I assume is for the compressor.....could the compressor (clutch) be pulling to much current causing this heat ? also where can I get a wiring diagram of this slider switch to check if my findings are correct ? Thanks guys.

 

well today again, I am trying to find out why the 12 volt input to the blower motor switch gets hot during high running. it is warm on med, but gets hot on high. and only when the compressor is running. vent is no problem. I ran a heavy Gage wire directly from the battery to the input on the blower fan switch (trying to isolate it from any other circuit in between), and when the A/C is on, the wire gets hot...and hot enough to burn you if you hold it in between your fingers for to long. the switch has a new plug installed on it and all 3 speeds work great so I know the resistor pack is working ( I installed a new one just to make sure) can anyone tell me how the compressor clutch circuit is associated with the blower speed switch ? I always thought that they were a separate circuit. why when I turn on the A/C does the 12 volt input to the blower speed switch get hot ??? Please, any help would be great, I have been pulling what hair I have left on this one...thanks in advance.

 

Try jumpering the feed wire to the A/C compressor directly to the battery.

That will isolate the clutch from the rest of the system. Then try your blower on all speeds and see if those wires still get too hot.

 

well I should have tried this from the get-go, and also listened to Autosurgen.
I took a wire directly from the battery directly to the hot wire on the blower it self and guess what...the wire gets real hot...so just like Auto Surgen said, the blower is bad and because low and medium run thru the resistor pack, the heat doesn't show it's ugly head..but high bypasses the resistors and goes directly to the motor thru the slider A/C max/nor switch, and it gets hot, but hooking it up directly to the battery bypasses the slider switch and the speed switch and since it gets hot...wala...bad blower motor...gonna get a new one soon...thanks guys for the input...hope this helps some one else...

 

Well I got a brand new Blower motor from the Jeep dealer here in Abu Dhabi, and put it in, and it also melts the blower fuse when I run it on high...it takes longer on vent than it does on Cool, but it also pulls to much current...can"t figure out why every blower motor ( 3 in total ) all pull to much current....even when I hook wires to the motor and run it straight from the battery, the wires and connections to the blower motor wires get hot....could I be getting bad motors from the dealer ? has any one had this problem ??? I am sure some one has....can I put a variable resistor in series in the hot side of the wire going to the fan motor to cut down the current ? any help would be great, also could some one please ohm between the 2 wires on there good blower motor and see what the ohms are ? I get a little over 2 ohms on this new motor I have...wonder if that is correct....thanks in advance.