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Topic: heater hose vacuum shut off

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heater hose vacuum shut off (1/3)
 4/14/19 11:15am
bcliffGold Member
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71 454 convertible, mulsanne blue,a/c, matching numbers, 48K miles

Joined: 5/5/2002
Posts: 313

I've noticed a bit more heat lately in the cockput and checked the heater hose shut off valve (new) and doesnt seem to be getting any vacuum on any setting on the heater/ac controls. Any suggestions on where to look first or what is usually the culprit with this problem. Thanks!


71 454/365 Mulsanne Blue Convertible

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Re: heater hose vacuum shut off (2/3)
 4/14/19 12:32pm
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Overland Park, KS - USA

1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 659

Assuming all of the other HVAC vacuum operated functions work normally, I would start at the control module and treat it like an electrical problem and see where you're losing the vacuum for the heater control valve.


1973 L-82 4 spd

Re: heater hose vacuum shut off (3/3)
 4/15/19 1:10pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19808

 Tom, do the doors on the system move when you change from Defrost to A/C to heat?(Air blows out where you want it to?) If not, first thing to check is vacuum AT the control switch from the engine. If all of the doors are operating properly, and you're just not getting a vac signal at the hot water shut-off valve, then you would need to trace the vacuum line from the switch to the valve. While you're at it, make SURE that when you turn the wheel to "Heat" or "Cold", that the vacuum AT the switch for the valve is working. Many times this problem is due to the switch itself drying out, and not directing vacuum to where it should. hth

|UPDATED|4/15/2019 10:10:27 AM (AZT)|/UPDATED|

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