Blower speed resistor or something else?

[rmasteller]

2006 LJR
Symptom: fan only blows on high speed, regardless of speed control selection.

For same symptoms, I replaced my blower resistor card once before and it worked. This was a 2 or 3 years ago(?), but less than 3,000 miles. Same symptoms now, new Dorman resistor installed, no change. I don't see any signs of melted wires. No signs of mice chewing, ever. See video.

View: https://youtube.com/shorts/_43dM3LIt58?si=1YxxSMRnZVE9zzIL

How do I actually test to find the fault? Can I test the resistance in this part? Can I use a multimeter on the speed switch? Can I determine if the fan is going bad and drawing too much power? I don't like throwing parts at a problem. I'm trying to learn to think logically, and learn proper diagnostic processes to be a better home mechanic. Thanks for your help.

 

[TheBoogieman]

Calling @macleanflood.

 

[rmasteller]

So, I pulled the new resistor out. There are of course 5 connectors, but I don't know which is for what. I assume the small connector is the power input and the 4 large connectors should have decreasing resistance to the first small one. I set my multimeter on 200ohms and systematically tested. I got the same values testing the same combinations of connectors on both resistor cards. Since I'm just guessing, does anyone know what proper testing is on this? Thanks.

 

[TheBoogieman]

I replaced my blower resistor card once before and it worked. This was a 2 or 3 years ago(?), but less than 3,000 miles. Same symptoms now, new Dorman resistor installed, no change.

I'd take it back and get another one just to rule out a defective part, since it takes 5 minutes to replace. I dislike Dorman parts and buy Four Seasons resistors.

 

[RangerTJ]

Mine is a 2000, but I experienced the same issue.

Replaced the resistor, but the problem turned out to be the actual fan control.

Replaced the entire control box (around $40 or so I believe) and that solved it for me.

Edit: Currently $33 for a 99-04.

THIS ONE shows that it fit 99-06 for $55

 

[rmasteller]

My resistor testing. What do you think?

View: https://youtu.be/XTJUvN6zW0A?feature=shared

 

[rmasteller]

I'd take it back and get another one just to rule out a defective part, since it takes 5 minutes to replace. I dislike Dorman parts and buy Four Seasons resistors.

I'm trying to learn how to determine faulty parts myself. Thanks for the brand recommendation!

 

[macleanflood]

Yes you should have different values across the pins. I think one is shared.

Pretty positive there's a complete test procedure with ohm values in the factory service manuals located in the resources section.

-Mac

 

[fizzlebottom]

Resistors in the pack are connected in series, so if all positions are testing the same (input to individual resistor leads) then something is definitely faulty. What is happening internally is that in the lowest position, all resistors should be in circuit. Turning the fan up removes resistors from the circuit, applying less resistance and allowing the fan to spin faster.

That still doesn't solve your problem. The actual switch may be faulty, always only selecting the lowest resistance setting. Or your pack maybe internally faulty somehow. You could measure resistance across resistor leads alone (1/2, 2/3, 3/4, 1/3, 1/4, etc) and compare. Or test the switch to see if it is possibly shorting and bypassing the resistor pack altogether.

 

[rmasteller]

Pretty positive there's a complete test procedure with ohm values in the factory service manuals located in the resources section.

Well, I don't see service manuals. There wiring resources, but I'm not an electrician yet, so I don't know how to use what I'm finding. There's a "trace" section, and that seems to just show you the relays involved. I don't know how that helps. Then there's a "flowchart" section which tells me the resistor is bad, which I already assumed.

I think I need someone to show me how this section helps. I've never seen it before, and wiring & electronics are a big weak spot in my knowledge.

 

[hear]

In the resources section here you'll find the FSM for your year. Section 8W has the wiring, but there's another HVAC section.

 

[fizzlebottom]

The testing procedure in the FSM only checks for continuity between all contacts. You can measure each individual resistor value by measuring resistance between pins 1&2, 2&3, and 3&4. They don't seem to provide resistor values at all in my '05 FSM.

Fan speed position 1 goes through resistors 1,2, & 3 in series.
Fan speed position 2 goes through resistors 2 & 3 in series.
Fan speed position 3 goes through resistor 3 alone
Fan speed position 4 bypasses all resistors.

 

[ColoJeep]

Mine is a 2000, but I experienced the same issue.

Replaced the resistor, but the problem turned out to be the actual fan control.

Replaced the entire control box (around $40 or so I believe) and that solved it for me.

Edit: Currently $33 for a 99-04.

THIS ONE shows that it fit 99-06 for $55

Years ago , I bought a resistor block to fix my issue on a 99 TJ , ( fan only on high ) without diagnosing anything . Of course that promptly bit me in the butt when changing it didn't do a thing . What I found was a cooked heater control panel . I got a new one from a MoPar dealer in the midwest for less than I could get it from a local dealer. It was $ 140.00 shipped . and the local guys wanted $ 180.00 plus tax. I got it through Amazon after my oldest daughter convinced me it was a real thing ! ( I thought Amazon was only a book seller ) this was in 2012 . The new panel was OEM and has worked fine since 2012 .

 

[rmasteller]

I found the FSM that I downloaded a few years ago. Only thing I see in Resources is the interactive wiring tool I mentioned above.

It does say to check for continuity, and my multimeter beeped checking every combination of connectors on both of my resistor units.

I didn't find the wiring diagram you posted. What's the page number for it? Learning wiring and diagrams is not easy! I found this one shown below, without the resistor or blower! Question: do I actually have both a A/C Heater Control and a Heater Control in my Jeep? And, what translates the listed connection numbers to actual connections on the device?

I'd like to follow the testing instructions for the switch.

 

[fizzlebottom]

What I posted comes from 8W-42-2 in my '05 FSM, though I realized its from the 'Heater only' section. It seems to be the exact same in the section including AC (8W-42-4)

 

[JKP]

Well, I don't see service manuals.

https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/

FSM, Parts Book, etc.

 

[JKP]

And if the resistor card didn't fix it, you fan switch is probably shot. And they didn't make the fan switch easily replaceable on the 05, 06.

 

[rmasteller]

@JKP I'd like to TEST the fan switch as described in the document I posted, but I don't know how to convert the wiring diagram into physical reality. I have no idea where to put multimeter probes. Can you help?

Also, replacing the part doesn't look like rocket science. What about it do I need to know?

 

[rmasteller]

My part number.

 

[JKP]

I should have worded that better, they don't offer the switch as a separate part, MOPAR only offered the whole assembly. I don't think anyone has started offering just the switch.