El Camino Central Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
36 Posts
Discussion Starter #1
My 1987 SS has very good AC but the clutch cycles in and out every second or two when I'm driving and have system on normal or max AC. My theory is that the individual retrofitting the system to 134a did not change the kickout switch which was dialed in for R12. Is there a way I can test this theory? I'm thinking of de-pressuring the system myself, replacing the switch with the 134a version and then vacuum pumping her down for a few hours and recharging with fresh 134 a myself.

Any gurus out there have tips or advice?

Thanks

Willman
 

·
Premium Member
Joined
·
5,751 Posts
For a free easy try - the switch is adjustable. Unplug the connector and there is a small screw between the terminals. Back it out a turn at aa time and try it or if you have gauges connect them and you can set the low side cycle pressure where you want it.
 

·
Supporting Member
Joined
·
4,406 Posts
Fast cycling is usually a sign of low refrigerant. Adjusting the switch might help, but I would get the levels checked with a set of gauges ( not too expensive at Harbor Freight, and worth having).
 

·
Registered
Joined
·
36 Posts
Discussion Starter #5
put a gauge on it, and see how low it is..
.
did it allways cycle fast ??
maybe there is a leak..
.
the switch should be on a port with a schrader valve,
shouldn't need to bleed/re-fill the whole system..
The high-side and low side pressures are bueno. Again, I suspect that the switch is an R12 variant and thus actuates differently when 134a is used. Thats a great tip on adjusting the switch- my '72 Monte Carlo had a more conspicuous diaphragm adjustment screw and after converting to 134a it worked poorly but adjusting that valve made that AC cold enough to make snowcones.....
 

·
Supporting Member
Joined
·
4,406 Posts
My experience shows that the switch adjustment will only gain a few PSI on the low side pressure before the clutch cycles. If no adjustment is made, the R-12 witch should cycle about every 8-12 seconds, but the vent temps would likely be above 40 degrees. Adjusting the switch would decrease the low pressure by a couple of PSI, which should increase the cycle times to maybe 10-15 seconds ( longer on really hot days). Vent temps should drop to the 37-39 degree range. No way to really set the switch without gauges. Too low on the cycle pressure, and you will freeze up the evaporator. I've seen vent temps in the 20's with R134a, with ice blowing out the vents, just before everything froze up!
 
1 - 7 of 7 Posts
Top