2000 HVAC Control Gremlin
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6th Gear
Joined: May 2024
Posts: 6
Likes: 4
2000 HVAC Control Gremlin
I’ve searched for this specific issue but trying to narrow down my issue.
2000 350, 6.8, 93000 Km.
HVAC works perfectly at idle.
At highway speed, the selector door seems to hunt and drop back to a mix position. It will go from the panel then be ok then by itself switch back. AC blows nice and cold. Blower seems to only blow at high.
At idle, all fan speeds work and the selector works fine. AC blows cold.
Assume it’s a vacuum leak but just hoping this rings a bell with someone and narrows it down.
4wd selector seems to be working just fine.
thanks gents.
2000 350, 6.8, 93000 Km.
HVAC works perfectly at idle.
At highway speed, the selector door seems to hunt and drop back to a mix position. It will go from the panel then be ok then by itself switch back. AC blows nice and cold. Blower seems to only blow at high.
At idle, all fan speeds work and the selector works fine. AC blows cold.
Assume it’s a vacuum leak but just hoping this rings a bell with someone and narrows it down.
4wd selector seems to be working just fine.
thanks gents.
Laughing Gas
Joined: May 2024
Posts: 906
Likes: 289
From: E TN
Not 100% sure on your truck but usually any system using vacum will have a reservoir and a check valve in the system. I'd check both of them to see if they are in good condition and if the check valve might not be sealing, it's made to hold vacum in the system when engine vacum drops.
Thread Starter
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6th Gear
Joined: May 2024
Posts: 6
Likes: 4
2000 6.8 Vacuum/HVAC Question
Update.
Check valve on the vacuum line in to the reservoir from the manifold failed.
Also, old silicone repair on a crack in the reservoir was leaking. Installed an inline check on that line and now the selector works properly at all rpm’s. No defaulting to defrost at highway speeds and rpm’s.
Check valve on the vacuum line in to the reservoir from the manifold failed.
Also, old silicone repair on a crack in the reservoir was leaking. Installed an inline check on that line and now the selector works properly at all rpm’s. No defaulting to defrost at highway speeds and rpm’s.
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