A/C gurus, bypassing my high side A/C pressure switch - so what, right? Just got my "84 to throw cool air - working fine, bit noisy, pretty sure it's the clutch. Anyway, I had to bypass the high pressure switch and replacements are more than I want to spend due to sharks knowing it's a discontinued part. I'm just going to leave it by passed. What's the worst that could happen? It has a functioning low pressure...

 

Blown line or seals, damaged compressor, condenser, or evaporator. It's there for a reason, but you may get lucky.

 

Okay, which one is it, the compressor mounted one or the system mounted one?

 

Hi
there are two pressure sensors on the small pipe from condenser to a/c box, one for high pressure compressor cutout a sensor with two spade terminals.
And the cooling fan request sensor (has a small round plug), you will need both connected.
If you remove the small round plug the cooling fan will stay on, which can reduce your pressures on a cool day.
If the high pressure cut out sensor is disconnected, the compressor will not disengage at high pressure and you can blow a hose or clutch slip.

The 84 has a sensor on the back of the compressor, not sure if that is a low pressure or high pressure sensor.....
If the sensor is not available new get a second hand one, best to keep everything working as it should.
There is a low pressure sensor for compressor cycling when the suction pressure drops with low evaporator coil temp, to prevent liquid refrigerant going back to compressor damaging the valves.

The sensors are all there for a reason and should not be bypassed or disconnected, otherwise a failure will result.
Could be right away with a blown hose or damaged compressor valves.

see links below to pressure sensors..

https://www.ebay.com/itm/NOS-GM-DELC...0AAOSwNDZbNurj

https://www.ecklerscorvette.com/corv...1984-1993.html

https://www.ecklerscorvette.com/corv...1980-1984.html

Pressure switch mounted on compressor below, this is the cooling fan request pressure switch on your 84 compressor.

https://www.ecklerscorvette.com/corv...1980-1984.html

Low pressure cycling switch mounted on large pipe at a/c box below.

https://www.corvettecentral.com/c4-8...q%3da%252fc%2b

 

Compressor, on back attached to high pressure line. Have recommendation to buy a MEI (Airsource) 1512 or 1513 switch. Looking into it will post results because it's reasonable cost alternative ~$20.

 

Thanks - checking this out.

 

Ha, yes agree luck would be involved - looking into a reasonably priced alternative.

 

As noted looking into alternative, thanks for the replies. Have another question about noise. I'm told these R4 compressors are typically loud, mine is but erratically. Best way I can describe it occasionally (every 20 seconds or so) it emits a loud grumbling/buzzing noise for about five-ten seconds. It's throwing cold air and consistently keeping the cabin cool on 90 degree + days. Anyone care to comment on the noise issue? Info - It's a R12 to 134A hack, had R134A fittings on it when I got it, been inoperative for years, changed seals, no leaks, added about 3 oz of Ester oil (under best guess on what was in the system previously), pressure readings very close to spec. Thanks.

 

My brand new R4 made noise too. Best way to describe it is like a rattling choke flap on a carb...

 

Hi
Sorry just realized some of the links don't work, see below for the compressor mounted cooling fan request high pressure switch.

See below for ones on ebay,,,,,, yeah i know it isn't cheap.....

https://www.ebay.com/itm/35756-4-Sea...Cclp%3A2334524

 

If you need it for some extra insurance, incase your fan quits, i have a cooling fan for $75 From an 86

Fan and shroud mount. Plug n play

 

And incase you blow your hoses apart:

 

did you ever learn if it works? I broke my high side switch changing valve cover gaskets :p and need a new switch but it seems my only option is used via eBay for some crazy prices

 

FYI on 1984 C4
'84 stands alone as the AC system is NOT controlled by the ECU of C4 generation

The small button switch on the back of the compressor is SanTech MT0671 (Murray 35967) (1984 only)
This switch and/or the cooling temp sensor (right rear of cylinder head) control the cooling fan relay and then the fan--ground either one and cooling fan engages
If installing new or used compressor, ensure correct switch is used or cooling fan will run at all times

The switch on rear of compressor (mounted on hose manifold) GM OEM part number 10007057
This is binary switch
Works as a high pressure safety switch (stops compressor running if pressure too high) AND low pressure safety switch (stops compressor from running if very low or out of freon)
Operates in the 10 psi to about 400 psi range (not exact specs)
Only available as new old stock--not manufactured any more from extensive research last year
Also used on Camaro and other GM to about 1993--look for other vehicles when doing scrap yard search

 

so, after some looking around the car, I figured out that the 1 pin red switch was broken and that’s why my cooling fan wasn’t working, and it looks like it’s gonna need a new compressor, yikes. Also the hi pressure switch while broken, I don’t really care because the system is empty and not in use anyway. So I had planned on converting to 134 in the future anyway, how do I deal with that switch at the back of the comp? Can I bypass that and rely solely on the temp switch in the head? Also, I have bypassed the control circuit for the time being so I can still drive it, and have just grounded the control side of the relay, so the fan now runs constant when ignition is on and ECT temps hang around 195-200, am I going to hurt anything by doing this?

 

Like in most cases --there is a work around
Yes, it can be left "as is" with fan running all of the time--side effect--does not get fully warm in specified time by EPA, lower fuel MPG

When replacing AC compressor with new--most likely will come without 'button switch' buy switch number mentioned earlier and attach one wire to wiring harness (OEM style) and other to good know ground--used compressor move old button switch to new/used compressor
Hiigh pressure switch is almost mandatory for safety--too high pressure--parts may explode--new compressor--"yikes again" and for no/low pressure--oil needed for compressor --if no 'fail safe' compressor will run with no freon/oil circulating--compressor 'lock up' running without oil--"yikes again"

 

yeah I could do that with the switch, I didn’t even know you could remove it from the back of the compressor. But as far as the high pressure switch goes the system is empty so I’m not worried about but blowing up, in the future I’ll work at a 134 conversion but for now the targa and windows keep me cool enough lol