Chris Welch
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• Soddy Daisy, TN, USA |
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• Registered on 4/6/2004 |
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• 2 posts |
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 Posted:9/6/2004 11:09 |
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I've searched and read on this forum about vacuum problems on the auto-hubs, but I've also found other stuff on the net saying the same vacuum setup runs the A/C stuff. My Autohubs are having issues, but when I shift into 4wh high, my ac changes and comes out of only the defrost vents, not through the dash. It takes forever for it to fix itself. Has anyone else heard of this or had this experience? Wanted to know where to check. I looked at the vacuum lines behind the glove compartment, all that is fine.
Chris Welch |
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dnevins
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• Subscriber since 12/29/2009 |
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• San Diego, CA, USA |
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• Registered on 12/28/2009 |
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• 340 posts |
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Chris, yes, that's a known combination on these trucks, and it fits your hubs acting up. The hubs and the HVAC vent doors share the same vacuum supply, and when there isn't enough vacuum the HVAC drops to the defrost vents by design. When you select 4x4 High, vacuum goes out to the front hubs. If a hub seal or one of the hub lines leaks, it drains the supply, the vents fall back to defrost, and it takes a long time to build back up. The lines behind the glove box are the HVAC end, so it makes sense they looked fine.
A leak at a hub is the most likely cause. To find which side:
1. Pull the vacuum line going to one front hub and plug it.
2. Shift into 4x4 High. If the vents stay where you set them, that side is the leaker.
3. If not, put it back and try the other side.
If plugging either side doesn't help, check the solenoid and the line from it to the hubs. A leak that only shows up in 4x4 is usually on the hub side of the solenoid, but owners have also found solenoids that leak only when they're switched on.
If the vents ever go to defrost when you're not in 4x4, look at the supply side instead. On a diesel the vacuum comes from a pump, so make sure it runs. Also check the check valve on the line to the vacuum reservoir.
Dana
https://partslogic.com |
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