Author Topic: 78 eldo air conditioner compressor cycles on and off  (Read 2035 times)

Offline steve eldridge

  • Posts: 18
  • CLC Number: 23943
  • Name: steven eldridge
78 eldo air conditioner compressor cycles on and off
« on: January 02, 2013, 10:51:05 PM »
 air compressor runs and line gets cold for about 10 seconds then turns off for about 1 minutes then starts again. has original freon in system, hope i can just change a super heat or limit switch with out losing freon. any one has an idea?  thanks happy new year!

Offline TJ Hopland

  • Posts: 10193
Re: 78 eldo air conditioner compressor cycles on and off
« Reply #1 on: January 02, 2013, 11:40:03 PM »
How long have you owned / operated this car?  What sort of ambient temps are you observing this in?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Re: 78 eldo air conditioner compressor cycles on and off
« Reply #2 on: January 02, 2013, 11:56:29 PM »
Steve,
It sounds like the system is cycling on the low pressure switch which, if it is the case is caused by a low refrigerant charge. In order to diagnose the system correctly, you have to install a test set of guages and record the pressures (both compressor discharge and suction when the compressor cycles off and then back on.
There is also a low temperature compressor cycling thermostat, but the way you are describing the cycling, I would check the low pressure switch (located at the rear of the compressor) first.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Offline steve eldridge

  • Posts: 18
  • CLC Number: 23943
  • Name: steven eldridge
Re: 78 eldo air conditioner compressor cycles on and off
« Reply #3 on: January 03, 2013, 12:10:42 AM »
just started working on this eldo. was in storage for a while. got it back to garage here in chicago cold now 30 20 degrees.
was in warm 70 degrees garage while i rebuildt the carb this weekend. and came outside to adjust carb idle screws and noticed motor pulling down rpm when compressor clutch came on for about 10 seconds. very happy to see line getting nice and cold but clutch turned off and cycles on and off.  have to go to my buddy to check with pressure gauges next week. thanks 4 the info!

Offline Guidematic

  • CLC# 19186
  • Posts: 879
  • CLC Number: 19186
  • Name: M. Jones
Re: 78 eldo air conditioner compressor cycles on and off
« Reply #4 on: January 03, 2013, 11:59:29 AM »

 Was the compressor staying engaged when the car was inside?

 Mike
1970 Fleetwood Brougham 68169
1985 Eldorado Coupe 6EL57
1988 Eldorado Biarritz 6EL57
1990 Brougham d'Elegance 6DW69
1994 Fleetwood Brougham 6DW69

Offline steve eldridge

  • Posts: 18
  • CLC Number: 23943
  • Name: steven eldridge
Re: 78 eldo air conditioner compressor cycles on and off
« Reply #5 on: January 03, 2013, 12:06:03 PM »
when car was inside warm garage i really could not run that long too much fumes! maybe i can go to a large heated garage in a shopping mall some day and run a/c in that heated garage. thanks, steve now here in chicago 20 - 30s temps

Offline Guidematic

  • CLC# 19186
  • Posts: 879
  • CLC Number: 19186
  • Name: M. Jones
Re: 78 eldo air conditioner compressor cycles on and off
« Reply #6 on: January 04, 2013, 10:12:02 AM »

 Normally with the CCOT system the compressor will not engage in colder temps, or cycle as you are experiencing.

 Mike
1970 Fleetwood Brougham 68169
1985 Eldorado Coupe 6EL57
1988 Eldorado Biarritz 6EL57
1990 Brougham d'Elegance 6DW69
1994 Fleetwood Brougham 6DW69

Offline mechanic80

  • Posts: 98
  • No good deed goes unpunished.
  • Name: Norbert Bartosiak
Re: 78 eldo air conditioner compressor cycles on and off
« Reply #7 on: January 04, 2013, 08:55:47 PM »
I thought the compressor would cycle in the DEFROST mode to dehumidify the air.  Am I mistaken?
mechanic80

Offline TJ Hopland

  • Posts: 10193
Re: 78 eldo air conditioner compressor cycles on and off
« Reply #8 on: January 04, 2013, 10:53:52 PM »
It will cycle on any mode other than off and econ (or vent? I think they called it on older models).
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

R Schroeder

  • Guest
Re: 78 eldo air conditioner compressor cycles on and off
« Reply #9 on: January 05, 2013, 09:11:34 AM »
I believe Greg hit it on the head. Low freon. If you saw the accumulator frosting up, then you are low on charge.
Wait until summer and recharge the system. I would do a evac, and recharge.
 Roy

Offline TJ Hopland

  • Posts: 10193
Re: 78 eldo air conditioner compressor cycles on and off
« Reply #10 on: January 05, 2013, 01:21:43 PM »
If he is going to drive the car over the winter do you think he would be best to unplug the compressor clutch till he gets it properly serviced and checked?

 My opinion would be unplug it.   Who knows what is in there for refrigerant and oil.  Hate to have it tear up the clutch or size up if it otherwise seems ok.   Getting cold is a good sign that its not just full of air but still safe seems better than sorry.  I have dealt with several cars that had been sitting that had ended up with enough air in the system that under warm conditions was under enough pressure to let the compressor cycle at least till it sized up.

Im too lazy to look up this system in the manual but is this like the mid 70's with that wacky valve capillary tube thing?  Or like the 80's with the orifice tube? 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Re: 78 eldo air conditioner compressor cycles on and off
« Reply #11 on: January 05, 2013, 01:52:29 PM »
Steve,
The absolutely worst thing you can do to an automotive AC system is let it sit dormant without running.  That is usually the cause of most refrigerant shortages.  The compressor sits idle, the seal dries out, and refrigerant 9and oil) leak out through the dry seal.  If the system had previously been working and (until it set unused for a while) this new symptom has just started I would (if this were mine) fully charge the system with R-12 and then be sure and run the AC (even if it is cold outside) for ten or so minutes every couple of weeks at the bare minimum.  If the seal hasn't been damaged by running dry up to now, the system should be ready for full operation in the Spring.
GregSurfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Offline steve eldridge

  • Posts: 18
  • CLC Number: 23943
  • Name: steven eldridge
Re: 78 eldo air conditioner compressor cycles on and off
« Reply #12 on: January 07, 2013, 12:24:49 AM »
 yes i have disconnected the clutch wire connection at the compressor. I always exercise ac systems once a month and will do a full evact and recharge in the spring time. thanks to all! steven eldridge

 

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