Resistors in HVAC housing?

 

can the resistor really cause it not to blow on any speed? i'm pretty sure that when you turn the fan speed to high, it bypasses the resistor completely. i've had like 12 jeeps (cherokees and grand cherokees though) and have dealt with a few bad resistors, but i don't think i've ever had one not blow at any speed, usually just missing one or two speeds.

 

I'd check the actual blower motor itself then.

 

blower motor is good, just tested by running power directly to it.

as i mentioned in my first post, i am getting 12v to it but when i plug it in, i'm not getting any juice LEAVING the switch. on the other hand, i completely bypassed the switch by jumping all the terminals on the plug itself and still not getting anything. at first it seemed like the switch is bad, but i can't get it come on by bypassing the switch and jumping the terminals either. so where does that leave me?

also note that i'm getting approx 2.5v to the blower motor resistor plug (although only through the brown with white (or tan, can't tell) striped wire) on speeds 1-3, and about .5v on high.

 

i had this exact problem on my cavalier; it ended up being the blower motor resistor. If any of the tracers on the circuit board are corroded, the blower motor will not work for that speed setting. hope that helps?

 

Did you check for power in the plug at the blower motor?

The plug itself? Or try wiggling the wires while it's plugged in.

I had a similar situation and it was a broken wire in the plug. I fabbed up a new piece and no more problem.

If resistor is bad, usually have high speed.

 

The mode select switch on the HVAC panel supplys the power to the fan speed select switch, check that switch to see if it's melted on the backside...

 

i have removed the ac control and checked the switches for any melting, and cannot see any. the plugs and connections look good.

i know this is a common problem, it was one of the first things i checked. i ended up ordering a used hvac control unit (including the switch) because it seems the most likely culprit at the moment. the i'm getting only 3v at the blower motor itself, and no more than 2.5v at the resistor, but am getting 12v to the 3 wire plug on the hvac controls, so i just assume the problem lies within the fan switch or the hvac control unit somewhere. hopefully this works

 

I had the same problem on my 99 TJ. I needed to get a new switch panel around $100. works just fine now.

 

just got the hvac controls today and installed, but it did not work. i haven't started testing for voltage or anything yet to see if anything has changed at the blower motor, the resistor, etc.

this is getting ridiculous.

 

just wasted more money on a new fan speed switch in case the other 2 were bad, but still nothing.

i've read that there was a problem on the 99 wranglers with a ground behind the instrument cluster somewhere that can cause the blower motor to not work, but i haven't been able to find an exact location yet for this ground. i'm running out of ideas and sanity.

 

I'm not sure which ground is the one you refer too, but there is one on each kick panel below the dash on the inside in the area of the wrangler sticker on the outside, and one under the panel below the steering column. those are the ones I know where they are, there are probably more but thats a start.

 

Try cleaning all connectors with some sandpaper, male and female. Also pull the fuses and clean.

 

the ground i'm referring to is here:

Re: 99 Jeep Wrangler Blower motor not working

it just mentions that the ground is a problem but does not say exactly where it is.

however, it seems now that i am not getting any power to the fan switch plug, which i previously said i did. the only place i'm getting 12v is in the skinny green wire going into the 3 wire plug behind the mode selector switch. the thick green wire goes to the fan switch, and the brown/white stripe wire goes to a green plug near the relay(which just connects 2 sets of wires, it doesn't seem to be anything other than a connector that you can test for voltage at or whatever), the brown/white wire then branches off into the blower motor resistor. i'm not getting any more than a fraction of a volt at either of these wires, at the fan switch plug or the resistor plug. that would seem like there's a problem with the mode selector switch then right, since i have power to it but not after it?

BUT, i just realized that the HVAC control unit i bought was for a jeep that has ac, and mine does not. so even if that mode selector switch is good, and even though it plugs right in, i'm not sure that it would work anyways since it's meant to be used with a jeep that has ac. so maybe my mode selector switch is bad? but if that were the case, shouldn't i be able to jump the terminals on the 3 wire plug and get the blower working? i tried jumping the terminals on the 3 wire plug and it's still not working.

 

have you checked the fan relay? possible its not closing the circuit all the way. i'm pretty sure its under the hood on the pass side in front of the batt. you could swap it with the start relay just to diagnose.

 

there's an ac relay next to the battery, but since i don't have ac on this wrangler it's empty. the blower motor relay is next to the resistor, which i have already checked and it's clicking when plugged in. i've also swapped in a different relay there just for the hell of it. those are the only hvac related relays i know of.

i disassembled the mode selector switch and found that 2 of the little springs inside the switch were not in place. all of the metal pieces inside the switch look great, not corrosion or anything unusual. i put all the springs back in place and put the switch back in but still nothing. i'd really like to know if this can somehow be jumped so i can determine for sure if it's the mode selector switch

 

Can you hear air releaseing when you turn the mode selector to different positions? You may have a leak in your vacuum lines somewhere. Check the vacuum line for cracks coming from the intake manifold. The blower will not work if the mode is not changing. Read this and see if it helps.
http://www.jeep4x4center.com/jeep-s...p-service-manuals/Jeep_Wrangler_TJ/1999/HeatingandAirConditioning.swf#toolbar=0

 

The blower will not work if the mode is not changing.

Not true...

 

have you actually changed the resistor??

 

no i haven't, i'm not getting power to it so why change it at this point? plus i don't have my high speed, which would still work if the resistor was bad.

 

OK man try this...........I pulled my dash back apart this morning when I got home from work. Pull the panel with your blower, heat and on off for the A/C defrost etc. Look behind the panel where the connectors are. I saw a small burnt look behind the far right side which controls the on off for the heat defr. settings etc. It is the big plug that has the blue,green, red, black, brown, and yellow wires coming to it. The small plug that is with that group is the one that is burnt on mine. I have the same year Jeep and 4 banger as you, it may be the same problem. Hope this helps........now I gota try to find some parts. I woulda posted some pics for you but my daughter has my camera......of course.

 

Here is a picture of the section.....All I did was put some insulated stake on's in place of the factory connector that was burn't. Now it's working like a top !!!! Hope this fixes yours. You might have to take the big plug off to see the burnt spot if yours has the same problem.

 

glad to hear you got yours working. i haven't seen any burnt areas anywhere on the plugs/wires/connections in the HVAC system but this was my next step since it's the only logical area i can have a problem at, considering that i have power to this plug and not after it.

i got my mode selector switch back together and DO hear air releasing when i change modes as cuder had mentioned a few posts back.

i cut the plug off that goes to the mode selector switch and wired the wires directly to the terminals but i'm still not getting the blower motor to work on any speed. now i'm going to see if i at least have voltage past this 3 wire plug now.

 

i give up. guess i'll never have a working blower motor

 

have you tired by passing the electrical portion of the mode selector switch? Try with your mulitmeter finding the hot wire and connect it to the wire that jumps the power across to the fan speed switch its possible that the mode switch is not allowing power through it with out showing up as a burnt terminal

 

yup, tried that with no luck.

 

I had almost the same problem and I went to the stealership to buy a fan switch and the parts guy asked if my fan swich was not working or if the highest setting was the only one working on the fan switch. I told him only my highest setting was working and he said I needed a blower motor resistor. I bought a Blower Motor Resistor, installed it in my Heep and the fan switch works on all speeds now. The blower motor resistor is not what you would think, it is a flat peice about the size of a credit card with a 4 or 5 pin connector on one side and two mounting holes. It was a little bit of a PITA to find as it is behind the bottom part of the dash behind the glove compartment. PITA to get to also but it only cost $20 bucks.

 

thanks but i'm very familiar with the blower motor resistors as i have changed many of them out on jeeps and other vehicles over the years. if your blower is working on high or just missing one speed, etc then yes, it's most likely the resistor, but if it's not working on ANY fan speed then it's not the resistor. the resistor only controls the first 3 speeds and is completely bypassed on the high setting. besides, i don't even have power TO the resistor, so my problem lies elsewhere.

 

Your ground wires are right side of dash below right ft. speaker, there are two of em, black & black w white tracer.
It sounds like your loosing a ground.

 

I'm looking at the same issue on a 2004 Liberty Sport 4WD. Blower suddenly stopped last night and won't blow on any of the four speeds (including high). Looking at Friday night for when I'll be able to really get into fixing this, but trying to come up with a game plan ahead of time.

 

Camosilver,Any fix yet?I have spent the last week working on a 99 TJ w/ AC with the same problems.I was charging the AC with the fan on high when it went out completely.Blower is new,Resistor is new,Relay is new,Ground connections are good and no burnt wires on the control switches.I have been able to get the blower to work by jumping the ground wire at the blower motor plug to the ground of the battery and the blower works at high speed with no control at the fan switch.Does this mean the fan switch is bad?Anyone have any ideas?Thanks.

 

It does mean you are missing a ground and if I was looking at the wiring diagram correctly the ground does look like it goes through the fan circuit.
Get an ohm meter and check the switch for continuity.

 

Thanks wushaw for the input.While replacing the fan speed switch I noticed the wire connectors to the selector switch were not factory and found that the ground wire was loose and replaced them fixing the ground problem.Hope this helps someone else having this problem.