Vacuum switch
'64 air coupe; replaced the heater vacuum switch twice, can't get any heat; vacuum on inlet is 12.5"hg, on outlet 11"hg. If I bypass switch i can get heat. Anyone run into this before? Thanks.
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Re: Vacuum switch
I'm referring to the switch behind the glove box which cotrols the hot water valve for the heater. Thanks.Comment
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Re: Vacuum switch
if bypassing the vac switch behind glove box yields heat, then the switch is bad. my orignal switch died years ago and i got the repo from long island corvettes, which is still functioning after 20 years.mikeComment
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Re: Vacuum switch
Thanks Mike; I'm on my second replacement from LI Corvette; they've been very cooperative in replacing the switch however I still have the problem.Comment
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Re: Vacuum switch
Thanks Wayne; does it mount the same ?Comment
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Re: Vacuum switch
The plastic switch mounts the same as the brass one. However the plastic switch that I used had a tendency to leak. This switch was made by Bill Greene of Bethesda, Md.Comment
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Re: Vacuum switch
Where did you buy the switch and did you ever cure the leak problem? ThanksComment
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Re: Vacuum switch
The late model switch should be available through most Corvette parts outlets. Maybe even still available at GM. I havent tried in a while. It does not mount the same. You use only one bolt hole and you may need to add a pad to the arm to activate the plunger. Seems like I had to reduce the rubber hose a little, but it works well. I have installed lots of them over the years.Comment
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Re: Vacuum switch
That plastic switch went disco years ago. And your right the hoses needed the use of an adaptor to accomodate it's smaller vacuum ports.
What ever happened to Bill Greene? I haven't heard his name in more than a decade.
Geoffrey Coenen
PS If the LI repro is like the original Brass switch; repair it with an o-ring lubed in high vacuum grease like used on PB seals.Comment
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Re: Vacuum switch
Geoff --- now that I see you're on the new DB and the subject is A/C vac switches, I've been meaning to ask you for clarification (in my feeble mind) on your instructions on how to replace O-rings. I copied your tips a ways back (I don't see them on your website now). I want to be sure I'm reading you right -- don't want to screw up an original piece. This is from my early '65, and I assume it's #3859356, Gr 9.275. The July '64 TSB says you should replace leaking valves with #3839651, which I assume is an earlier issue ('63 & 64 ?), but my parts books and parts history books show no indication of the '651'.
Anyway, I just want to confirm the ends of the valve that you're refering to. Straighetn out the 4 crimps at 'B' ? Unscrew the tip of the pushbutton (end 'A' ?) and the shaft will slip out of the switch (huh ? from which end ? slides towards 'B" ?) When you undo the crimps at 'B' does that brass sleeve/guide slip out or does it unscrew ?
TIA (Dr.R's perscription reprinted below)
Dr REBUILD's Corvette Parts (also see '64 TSB #1012
re change in switch)
TIP
HOW TO REPAIR A LEAKY BRASS 63-67 AC HOT WATER SHUT
OFF VACUUM SWITCH
Note that on the end of the switch opposite the
push button, the metal is crimped in several
places. This crimping prevent disassembly. Use a
small flat bladed screwdriver and ball peen hammer
to straighten out these crimps. Unscrew the tip of
the push button and the shaft will slip out of the
switch. Do not loose the small spring inside. The
shaft has a flat rubber O-ring to seal against the
inside walls of this essentially hollow switch.
Often this rubber is cracked or worn and will not
provide a seal against the wall. Using a vernier
caliper, I measured the bore ID of the switch and
the OD of the shaft. Replace the original flat
O-ring with a standard round O-ring. After cleaning
the switch & shaft, lubricate with a vacuum grease
as used on a vacuum power brake booster. Reinsert
the shaft, return spring and carefully re-crimp the
end as original. My original switch performs like
new in my 67 AC model and if it ever wears out
again I can replace the O-ring for less than a
dollar. It has been several years since I repaired
my switch and do not want to disassemble my Vet to
measure it again. Look up companies that sell
bearings in the yellow pages and take your
disassembled switch to them. They will have a
vernier caliper to take the measurements and can
supply you with the O-ring. For two bucks you can
get a lifetime supply. Vacuum grease can be found
at most auto parts stores. Remember you read this
tip here first, so next year when you read this
same tip in other catalogs, you will know who the
sheep really are. Baaaaaaaaaa !Comment
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Re: Vacuum switch
Wayne,
It was the 4 crips at B. I don't even recall the ones at A. But once I figured the knob came off, I saw I could get the rest of the to slide out the back end.
This is from memory, but your switch does look a little shorter than mine - but remember I rebuilt this switch 20 years ago for a car that has been on the road again now 10-15 years with roaring cold AC. I didn't take pictures.
However last summer I notice the AC wasn't cold as usual so if it's not solved by it's first R12 shot in 20 years, I'll check that switch. No exaggeration the AC blew colder than my C4 and C5. I have no doubt it will return to this peak performance again with little parts.
Geoffrey CoenenComment
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Re: Vacuum switch
On my 67, applying vacuum to the hot water valve in the engine compartment allows hot water to flow through the heater core. So, if you have 11 inches of vacuum on the outlet of your vacuum switch, I think that should do the job. Something doesn't sound right.Comment
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Re: Vacuum switch
All that I know is that when I bypass the switch, it puts 12.5"hg on the valve and the valve opens allowing hot water into the core; with the switch in place, I get 11"hg and the valve doesn't open and I get no heat;thanks. Anybody have any idea on the O-ring size needed as indicated by Dr Rebuild?Comment
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