I've got a 92 K1500 Pickup with 350 engine. My problem is that the A/c
compressor never cycles. It stays on all the time. I have replaced
the "cycling" switch on the acumulator with no change. I have replaced
the A/C control head too. All the A/c compnents are in good shape and
function fine. Anyone experience this problem and get it fixed?
The cooling system is fine and everythins else to my knowledge is
working ok. From the time the A/c system is turned on the compressor
runs continously. After some time the A/C light will start blinking
on the dash and the A/c stops working. You can clear the codes
and the A/C sytem will start right back up and work fine, until it
reapeats the same problem. Any ideas?
Ditto on the same truck: Doc?
Buddy had three complaints when he gave me the truck: No, A/C, cruise,
or tunes. 1992 GMC Z-71 5.7 "K" engine
Hot as hell so I figured that I would give him A/C first:
Converted the system to R-134A.
Recover, recycle, recharge, no leaks.
A/C flashed on the control unit.
Noticed lime green wire from cycling switch on accumulor while
checking relays goes to ECM.
Reset ECM, A/C cold and normal.
Diagnosed radio, replaced amp with boneyard unit, would not play until
ECM reset. Hmmm.
No cruise, replaced multi-function switch. No cruise. Replace Cruise
control module with brand new 30 bucker I found on eBay motors, no
cruise. rest ECM, no cruise. Well, two out oif three (I swapped out
the new multi-function switch) in the meantime.
Are we seeing cracked boards, ECM updates, speed dens?
On Sat, 26 Jul 2003 02:47:15 GMT, Elbert Clarke
I've been down a similar path.
first got the truck it was fairly rough. Truck was already set for
134A. Repalced compressor, accumulator, condensor, orfice tube...
all with GM-Delco parts... no leaks, pulled vaccum... runs cold.
then intermittant problem with A/C light and a/c system shutting down.
I replaced the cycling switch and the A/C control head...both with
GM-Delco parts. I've resetted the ECM to many times to count at this
Surely the A/C cycling function is not controled by the ECM?? I don't
have a shop manual on this truck but I've been thinking about getting
My A/c works and it does get cold but if you run the A/C all day , at
some point in time the A/C light flashes and the A/C shuts down. I
bleive its a pressure problem since the system does not cycle on and
off like its supposed to.
Does your A/C cycle on and off ??????
My radio sucks... it works but has bad static (I'll screw with that
The system is most likely overcharged. The system cycles when low-side
pressures reach the point where the "cycling switch" more properly known as
the low-pressure cut-off switch kills the A/C compressor clutch. When the
pressures creep back up the system kicks back on. An overcharged system
will never cycle because low-side pressures never reach that point, and an
undercharged system will cycle constantly as the pressures are always
dropping below the kill-switch level.
R134a systems also have high-pressure cut-offs, but your trucks likely won't
have them as they were desgined for R-12 (a proper retrofit includes a HP
switch, but few actually do it!).
What kind of low-side pressures are we seeing on these trucks @ 2000RPM,
engine fully warmed up, A/C cranked on a hot day?
For the life of me I cannot find the link but this seems to be a common
problem with the AC flashing. I know the book says it indicated low
pressure/ the compressor cycles for 10 consecutive times for less than 1.5
seconds each set the fault.
I have seen but cannot locate the information online about fixing the
control head. Basically you cut one wire from the control head and splice it
to another (I believe ground). I was navigating this site and its links when
I saw it but cannot find it again. good Luck
As for the static in the radio ck the antenna where it enters the amp behind
the ashtray. Mine was allowing water to seep down and corroded the end on
the antenna at the amp. I managed to salvage it, but eventually replaced the
radio with a head unit from Crutchfield. Best thing I ever did.
Looks like that mean tearing into the dash pretty good.
Its easy to get to the A/C control head, but getting behind
the connector where the control head connects at teh dash
will be a pain in the rear...... I'm not sure what type connectors
they are talking about since I belive the control head has blade type
single connector that fits in a female plug on the dash.......
On Thu, 31 Jul 2003 00:00:37 -0400, "Mastermech"
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