HVAC

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HVAC

Postby sirrick4 » Tue Jun 15, 2021 7:17 pm

OK I'm trying to redo the wiring in the HVAC system. So far I've checked out 4 different wiring diagrams and nothing matches what is in my car and it's doing my head in. I am thinking of putting my own new wiring in to replace the mess behind the dash. My A/C system has been completely replaced and everything is new so that I can use R134a gas. We can't get the old type gas - I think it was R12 - here in Australia. Questions: What in blazes is a RANCO switch? It lies between the pressure cut out and full throttle compressor cut-out and is also connected to the idle stop solenoid. I have tried everywhere and all I can come up with is the name of a company that makes thermal switches. My thinking is this - I reckon I should be able to do away with the engine thermo switch, idle stop solenoid, full throttle compressor cut out and the ranco switch. Does anyone have any thoughts on the matter or should I just bite the bullet and go and see a sparky? Thanks in advance.
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Re: HVAC

Postby Monza Harry » Wed Jun 16, 2021 5:15 pm

Sirrick, I haven't "Dove In" to my AC wiring yet, but is it possible the idle stop solenoid is actually a fast/high idle solenoid to bump up the idle with the added load of the A/C compressor? The solenoids are visually /functionally the same/similar but I'm just not sure if the stroke/travel is the same, it would be adjusted differently, to maintain the idle speed with the extra load instead of killing the engine on shut down. The full throttle switch is for reducing drag while trying to pass/climb a steep hill... and to protect the compressor from overspeed as well, this also has the added benefit of adding less heat to the cooling system during its' highest demand. Just some points to consider, or research before deciding on your final/next plan of attack. As for a RANCO switch, :? Sorry I couldn't be of more Help, Harry.
I'm not a hoarder I'm a preservationist 78 Monza Spyder (Soon To Be 2+2 with Spoilers)
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Re: HVAC

Postby sirrick4 » Wed Jun 16, 2021 8:04 pm

G'day Harry, thanks for the reply. My thoughts were the same with the idle solenoid and the full throttle cut-out but I'm pretty sure they were on the original carby. When I bought the car it had an Edelbrock manifold and 600cfm carby so there was no solenoid there, nor were there any wires. The whole wiring harness was fairly well butchered and much of the wiring was missing or changed in the engine bay and behind the dash. In fact anything to do with the A/C in the engine bay was removed. Kind of strange for a CA car. I thought it got hot there in summer. :lol: I guess I will keep plodding along, Thanks for the advice on the full throttle switch, I'll keep that in mind.
Cheers, Rick
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Re: HVAC

Postby zeke » Thu Jul 08, 2021 2:32 am

Dunno how they came up with "ranco" but it is just a normally closed thermal switch. The temp bulb goes on the evaporator coil liquid line and if the system gets too cold, it cuts out the compressor to keep from freezing the coil.
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Re: HVAC

Postby sirrick4 » Thu Jul 08, 2021 7:21 pm

G'day Zeke.

I thought it may have been for that. I've got an adjustable thermostat wired in sequence to the pressure switch so I figured I could ditch the ranco switch and the other associated stuff. I'm slowly getting there.
Thanks for the reply. Cheers
Rick
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Re: HVAC

Postby zeke » Fri Jul 09, 2021 6:49 am

A/C Thermo switch actually shows up if you look under 1977

https://www.rockauto.com/en/moreinfo.ph ... 4&jsn=1380
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Re: HVAC

Postby zeke » Sat Jul 10, 2021 5:11 am

When you order FS 35720, this is what shows up and it actually says RANCO on it lol. I'll guess "range compressor"
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