MONTY Posted August 6, 2021 Share Posted August 6, 2021 Morning Moses hope all is well in your neck of the woods. My 97 TJ blows out the defrost only. Alot of forms say vent door actuator. Well maybe. During testing with the motor running I slide the controls though defrost, floor, dash, AC, AC recirculate, I find that there is no movement at the diaphragms. To me that implies I have a vacuum problem. I'm not sure how/where to to test for vacuum and keep it isolated to the hvac area. Is there something else that I need to look for?? Thanks, Roger Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted August 6, 2021 Administrators Share Posted August 6, 2021 Hi, Monty...Trust you're doing well and staying busy in good ways! First-off, the TJ HVAC system has a vacuum reservoir. It is not unusual for the vacuum source to the HEVAC vacuum reservoir to have a hose leak, deteriorate or leak at the reservoir. Locate the reservoir and trace the vacuum source there. Check for consistent vacuum to the reservoir and to the check valves after the reservoir. I had a vacuum loss on our '99 XJ (similar) that would shut off the cruise control on a grade and shift the A/C flow to the defroster only. I traced the vacuum supply from the reservoir and found that the vacuum hose was directly beneath the battery box. Corrosive debris over time had etched through the hose. The leak was not noticeable unless engine manifold vacuum dropped. When engine vacuum was low (climbing a grade under throttle), there was not enough vacuum to operate the heater and A/C flaps or keep the cruise control diaphragm working properly. Try the vacuum source issue before plunging into the HVAC or HEVAC plenum and vacuum motors. You can test each vacuum motor simply enough with a hand vacuum pump. In fact, you can test the plenum flap movement this way with the A/C and heater operating to see where the air flow goes when vacuum gets applied. This is a quick way to troubleshoot the HEVAC and HVAC functions. Again, the first place I would look is the vacuum reservoir and vacuum supply sources or hoses. If the issue were temperature control, I would be checking the control cable that attaches to the dash control unit. A loose or broken control cable is often the source for temperature control issues. Schematic drawing of your HEVAC components: 1997 Jeep TJ HEVAC Components.pdf Moses Quote Link to comment Share on other sites More sharing options...
MONTY Posted August 6, 2021 Author Share Posted August 6, 2021 Well I found the problem as you can see in the 1st pic. The 2nd pic shows the route that i can see. In the 3rd pic there is a black hose. Is it possible to tap into that hose. (Some I doubt it). Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted August 6, 2021 Administrators Share Posted August 6, 2021 Monty...Glad I could point you in the right direction. You would have wasted a great deal of time removing the HVAC plenum and fiddling with the duct flaps. Shops charge customers hundreds of labor dollars chasing down these issues. You have a manufactured vacuum harness here. This PDF is the line drawing from the FSM. You can zoom into the PDF for detail. Note the check valves and other items that need to remain in the system: 1997 TJ Wrangler Vacuum Rerservoir Schematic.pdf The factory tube with check valves may still be available if you want to replace the entire Mopar piece. If not, you'll need to splice-in tubing at the damaged section or construct a tube section, keeping the check valves in place. If you look closely, there is a section from the reservoir to a check valve near the firewall. If you get bulk tubing, you can fabricate the tube section from the reservoir to the first check valve to restore the system. To duplicate the curves and radii, use a hair dryer or heat gun. This is plastic, so practice with a few spare pieces before forming the final tube. A quick repair would be Dorman 'Help!' parts from the local parts house. The link to Amazon finds vacuum connectors, tubing and assorted parts. Dorman makes 'Soft Vacuum Tubing connectors' and simple tubing splice connectors. Tubing is available in bulk. There is a market full of repair parts for this tubing. If you can't find what you need at the local parts house or Amazon, see Dorman's full catalog online: https://www.amazon.com/Dorman-Help-47417-Hard-Hose/dp/B0006305N8 If you want color plastic vacuum tubing, it's also available... Moses Quote Link to comment Share on other sites More sharing options...
MONTY Posted August 8, 2021 Author Share Posted August 8, 2021 Well Moses you are The Man😁. When it comes to working on the dash I think I'd rather drive my Rig thought Boston. I was prepared for the worse in what turned out to be a painless fix. I bought 2 packages of Dorman vacuum connectors ( I needed 2 1/8 in connectors ) and 2 ft of 1/8 in tubing, all for just under $10. Removing the glove box I then removed 2 screws and pushed the fuse box out of the way. 2nd pic. That allowed me to get 1 hand in and pull the busted vac tube out. 1st pic. I cut of the ragged end, attached 1 of the vacuum connectors and then the 2ft of tubing. I then feed the tubing though the firewall, you can see the hole in the 2nd pic. At this point I attached the 2rd connector to the vac tubing shone earlier in this thread. At this time I fired her up and BINGO, EVERYTHING WORKED! Hell that wasn't so bad I remember thinking LOL. Before I buttoned her up I slid a rubber grommet over the tubing and into the firewall. 4th pic. I finished zip tying the hose in place making sure the Vacuum tubing connector was in the grommet for added protection. Moses thank again! I hope all this helps someone else Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted August 8, 2021 Administrators Share Posted August 8, 2021 Suitable fix, Monty! Others will benefit from your approach...Glad this worked out well. Moses Quote Link to comment Share on other sites More sharing options...
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