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Author Topic: 68 Eldorado A/C relay switch  (Read 1109 times)

Offline Forgiven1989

  • Posts: 85
  • Name: Dave Gipson
68 Eldorado A/C relay switch
« on: February 09, 2013, 07:36:23 PM »
The compressor on my 68 Eldorado didn't turn on today.  It worked fine last year.  I wonder if it could be the A/C relay?  Also does anyone know where it is located on the Eldorado?  I think it is on the firewall right behind the engine.  Thanks.

Re: 68 Eldorado A/C relay switch
« Reply #1 on: February 09, 2013, 08:01:33 PM »
Dave,
Does the fan work when you turn the selector lever to 1. High, 2.Defrost, 3. Automatic?
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 Forgiven1989

  • Posts: 85
  • Name: Dave Gipson
Re: 68 Eldorado A/C relay switch
« Reply #2 on: February 09, 2013, 09:16:22 PM »
Greg,  The fan works in all modes.

Re: 68 Eldorado A/C relay switch
« Reply #3 on: February 10, 2013, 05:03:15 PM »
Dave,
If the fan works (and nothing has been changed since the system worked correctly) I would check the connection at the compressor clutch.  Check the positive side for power and check to see that the ground wire has not come loose somewhere.
If there is no power to the posit5ive side of the connector, check the thermal limiter  (it is called a switch, but it is a one time opening fuse) located on the engine side of the heater air box on the passenger side of the car. IF the system was short of refrigerant, the compressor mounted switch grounds the circuit, causing the slow blow fuse to heat up and open the compressor circuit, saving the compressor from undue abuse while the refrigerant (and presumably the oil level) is low.
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 Forgiven1989

  • Posts: 85
  • Name: Dave Gipson
Re: 68 Eldorado A/C relay switch
« Reply #4 on: February 10, 2013, 07:26:08 PM »
Thanks Greg I will try that.  Dave

Offline cadillactim

  • Cadillac Tim
  • Posts: 796
Re: 68 Eldorado A/C relay switch
« Reply #5 on: February 11, 2013, 07:49:56 AM »
The thermal limiter switch didn't start until 1972.  The compressor switch may be bad. The switch prevents the compressor from engaging if outside temperature is below freezing. 

Tim
Tim Groves

Offline Forgiven1989

  • Posts: 85
  • Name: Dave Gipson
Re: 68 Eldorado A/C relay switch
« Reply #6 on: February 11, 2013, 12:51:56 PM »
Tim, Do you know where the compressor switch is located?  Thanks.

Offline cadillactim

  • Cadillac Tim
  • Posts: 796
Re: 68 Eldorado A/C relay switch
« Reply #7 on: February 11, 2013, 10:01:26 PM »
It's on the cowl under the hood on the passenger side. The compressor switch and ambient sensor are one unit.

Tim
Tim Groves

Re: 68 Eldorado A/C relay switch
« Reply #8 on: February 11, 2013, 11:39:23 PM »
Dave,
I just noticed where you are located.  The compressor lock out switch is located in the outside air duct and senses outside temperature. When the outdoor temperature drops to (about) 32 degrees F, the contacts on the switch open and keep the compressor from running.  If the car is outside and it is that cold, perhaps the switch is functioning corectly.
Once you find the switch (and ambient sensor) you will notice there are two pairs of spade connectors.  If you have an ohm meter, with the plug from the system disconnected, check the resistance between the two connectors of each pair.  The compressor lockout will either be 0 resistance or an open circuit as indicated by a reading of "infinity".
Depending upon the ambient temperature the other pair will show a resistance that varies with temperature. 
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 Forgiven1989

  • Posts: 85
  • Name: Dave Gipson
Re: 68 Eldorado A/C relay switch
« Reply #9 on: February 12, 2013, 07:16:49 AM »
Thanks a lot guys.  I'll look for the switch today.  Dave

 

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