Jeep Wrangler HVAC Repair - Jp Magazine

Pete Trasborg Brand Manager, Jp

In the story “Jeep Fire Prevention” (Oct. ’07), we showed you how to wire relays into your ’99-and-up TJ heater system to help combat the melted switches and wires that can be caused by a worn or dying blower motor. As part of our swapping and wiring, we put a cheapo parts store blower motor in the Jeep and figured we’d be good to go. We got about 7 years and 120,000 miles out of our factory blower motor, but the replacement only lasted 2 years and about 20,000 miles before we were having problems again.

safe Heat jeep Wrangler Computer And Battery Photo 40644123

We were cruising along one rainy day with the defroster on and smelled burning electrical parts just after we noticed the blower motor speed decrease. Once you’ve gotten a whiff of the acrid smell of burning electrical parts, you never forget it. So, we knew we weren’t having flashbacks to the time Randy was blamed for that honky tonk burning down. Our hvac system was on the fritz again.

Needless to say, 20,000 miles for an hvac system fix sucks, so we did some more research this time. After examining the old parts in the dash and tapping some companies with experience in this sort of thing, we came up with a plan of attack. There is no reason we shouldn’t see more than 100,000 miles out of this round of repairs, and here’s how we did it.

PhotosView Slideshow We cut some corners last time by re-using our fried switch panel and going with the cheapest blower motor we could find. Rather than use the local parts store, with the kid who thinks a Compass is a “phat Jeep,” we went to Collins Brothers for the parts. Collins Brothers has been restoring and modifying Jeeps for years and knows good Jeep parts when it sees them. In addition to a new Mopar switch panel and resistor, we got a new Crown Automotive blower motor and some good take-out wiring to plug into our new switch panel. After speaking to Jon Delucia at jeepair.com, he verified our suspicion that the blower motor was drawing too much power. A new blower motor shouldn’t draw any more than 15 amps on High. A worn motor that might cause problems will draw 20 amps or more on High. If you test yours and it is pulling more than 20 amps it is likely time to replace the motor. Fortunately, the blower motor on the TJ is much easier to get to than any of its short-wheelbase ancestors. Simply remove the computer and battery and it comes out by removing just three bolts. We get a lot of questions about the resistor in the HVAC system. It seems redundant, but the blower motor can never move more air than it can on “Max.” So, to get different speeds out of the motor, it is slowed down with a resistor pack (arrow). The resistor pack heats up, so it is placed in the heater box in the flow of air to help cool it off. It can go bad without the blower motor also being bad. Typically, a failing resistor pack is evidenced by a loss of speeds. Despite being able to see the resistor pack from outside, it needs to come out through the interior. Go in through the passenger-side door, look under the dash, and you’ll see something like this. The plastic beauty panel is retained by four hex-head screws. Don’t break your panel during removal; but even if you do, it won’t affect the operation of the heater or A/C. It is there to make the heater look better and kill some of the interior noise. Once you’ve got the beauty panel off, you’ll see the resistor pack behind it; it is easily removed with two screws. If your wiring has been through as much as ours has, you might notice your wires are discolored. This wire was so toasted it was discolored 1⁄2-inch back from the connector. We cut off all of the nasty looking conductor until we had good, clean copper. We then cut the take-out wiring from Collins Brothers to length and soldered it to our factory wiring. Thanks (at least in part) to our relay solution from last time, we only had to replace the wiring and connector at the range selector switch. We were taking no prisoners this time, and replaced our old controls (below) with the new ones (above). The Mopar controls come with about 18 inches of new vacuum line and connectors. We weren’t having any vacuum-related problems, so rather than dig our old vacuum stuff out of the dash, we reused our existing vacuum harness. There were several running changes to the control panel. Look on the bottom for the sticker to see which one you have. While we’ve seen earlier ones, the latest we’ve seen was marked as Revision E, Change C. Having the latest doesn’t exempt you from problems, though. Our old melted one was Revision E, Change C.