Jess Posted January 25, 2017 Share Posted January 25, 2017 Recently I did some "repairs" to my 89 MJs HVAC system, new Blower + resistor, bunch of other crap. I've been experiencing a phenomenon that I don't remember pre-HVAC repairs where the Blower slows to an almost stop when I'm accelerating up a hill and the RPMs are high, once I get to the top and shift, the blower speeds back up. The problem is I almost never notice it untill it speeds back up so I'm not positive on the conditions which it occurs. I just know I notice it more when climbing hills. Could this be a battery problem? I was thinking vaccum at first but there isn't any lines in the blower that I can recall so that doesn't make sense. Link to comment Share on other sites More sharing options...
Hippie66 Posted January 25, 2017 Share Posted January 25, 2017 Recently I did some "repairs" to my 89 MJs HVAC system, new Blower + resistor, bunch of other crap. I've been experiencing a phenomenon that I don't remember pre-HVAC repairs where the Blower slows to an almost stop when I'm accelerating up a hill and the RPMs are high, once I get to the top and shift, the blower speeds back up. The problem is I almost never notice it untill it speeds back up so I'm not positive on the conditions which it occurs. I just know I notice it more when climbing hills. Could this be a battery problem? I was thinking vaccum at first but there isn't any lines in the blower that I can recall so that doesn't make sense. Following... Same issue on my '89, except I think the blower may remain blowing the same, but switches to defrost, which changes the sound. Almost 100% positive we're both dealing with a vaccum issue. Link to comment Share on other sites More sharing options...
Minuit Posted January 25, 2017 Share Posted January 25, 2017 It's probably doing what Hippie66 is talking about. It's probably not actually slowing the blower down, it's just losing vacuum and blowing through the defrost vents. Next time it does it feel for air coming out of the top of the dash. If air starts coming from the defrost vents, you've got a vacuum leak somewhere between the engine and the HVAC system. A good place to start would be the vacuum container behind the bumper. Trace the line coming from it for any damage, and make sure the vacuum line is pushed into it all the way. There's also a connector near the blower motor on the firewall that you might have accidentally bumped when changing the blower. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted January 26, 2017 Share Posted January 26, 2017 It's a vacuum issue... Check for air flow through the defrost vents when you next climb a hill. Link to comment Share on other sites More sharing options...
Jess Posted January 30, 2017 Author Share Posted January 30, 2017 Following... Same issue on my '89, except I think the blower may remain blowing the same, but switches to defrost, which changes the sound. Almost 100% positive we're both dealing with a vaccum issue. Interesting. Is the defrost always quieter than the heater? Mine is almost the exact same sound. You guys were right though, the defrost starts blowing when I'm climbing. My reservoir thing in the bumper isn't screwed in anymore so it's been bouncing around for awhile - I'll have to take it out and give it a once over. Link to comment Share on other sites More sharing options...
Hippie66 Posted January 30, 2017 Share Posted January 30, 2017 I need to go over my MJ and ZJ to track down vac issues. My ZJ started having vac issues after backfiring due to a bad PCM Link to comment Share on other sites More sharing options...
64 Cheyenne Posted January 31, 2017 Share Posted January 31, 2017 Smoke test to find the leak. Have a smoker blow smoke into a vac line....look for leaks. Link to comment Share on other sites More sharing options...
cruiser54 Posted February 2, 2017 Share Posted February 2, 2017 If you want a more powerful blower on a Renix, with less likelihood of burning the brown wire on your ignition switch, do this: http://cruiser54.com/?p=211 Link to comment Share on other sites More sharing options...
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