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Old 07-15-2010, 07:07 PM   #1
tucsonjwt
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Location of HVAC Vacuum Switch - 83 C20

Where is this vacuum switch for the A/C on my 83 C20 located? Thanks.
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Old 07-16-2010, 12:15 AM   #2
Jonboy
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Re: Location of HVAC Vacuum Switch - 83 C20

I am pretty sure that mounts to the back of the A/C control head in the dash.
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Old 07-16-2010, 12:50 AM   #3
tucsonjwt
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Re: Location of HVAC Vacuum Switch - 83 C20

I don't see it on my HVAC control. My control has a round black object with 5 vacuum lines coming out of it. This is a neutral color and is supposed to have 9 vacuum lines attached to it. I have the dash torn apart and still can't see any trace of this part. It obviously fits into some kind of electrical connector, then has vacuum lines attached to it.
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Old 07-16-2010, 08:26 AM   #4
ElGracho
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Re: Location of HVAC Vacuum Switch - 83 C20

Nowhere. That one fits 84-87.
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'84 Chev C10 Short Wide - Super duper plain (manual steering, manual brakes, no dome light, no cig lighter)
'85 Chev C10 Short Wide - Super plain Vortec 4.8 4L60E trans
also: '81 K30, '83 C30 Crew Dually, '84 M1028 CUCV, '85 M1009 CUCV, another '85 C10 SWB, '89 R3500 Flatbed
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Old 07-16-2010, 08:27 AM   #5
Jonboy
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Re: Location of HVAC Vacuum Switch - 83 C20

If it isn't the switch on the control head, then it must be the one on top of the heater box. I have just had a brief glimpse of mine; I was checking by feel to make sure everything was attached. Should be behind the glove box, and you will probably need to drop the floor duct and the duct going to the defrosters, too. Not a bad time to replace the foam weatherstripping, either.
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Old 07-16-2010, 10:51 AM   #6
tucsonjwt
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Re: Location of HVAC Vacuum Switch - 83 C20

El Gracho - I sure want to agree with you - don't look forward to more disassembly of the ductwork. But, if Jonboy has one on his 79 - and the catalogs says it should be on my 83 - it makes me wonder...
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Old 07-16-2010, 06:09 PM   #7
tucsonjwt
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Re: Location of HVAC Vacuum Switch - 83 C20

Nothing on top of, or anywhere around, the heater box. Lots of vacuum actuators, but I followed the vacuum lines and they just go to various vacuum actuators. I don't see 9 vacuum lines anywhere in one spot, which is what this switch requires.
El Gracho, I believe you are correct. I am done looking for this switch. I think the vacuum valve at the heater control itself with 5 lines must do the job of this switch.
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