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A/C switch-relay question-68 442

Old September 9th, 2012, 08:27 AM
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A/C switch-relay question-68 442

I have two questions regarding a malfunction in the A/C of my '68 442:

1) I must move the dash switch repeatedly back-and-forth from Vent to Normal/AC to Recirculate before the A/C compressor will engage and come on.

Toggling the dash switch repeatedly will not turn the compressor off.

If I leave the dash switch in the Normal/AC or Recirculate position and turn off the engine, then the compressor and A/C will come on when I re-start the car.

If I move the dash switch to Vent, Heat, Defrost or Off and turn off the car, the compressor stays "off", when I restart the engine. To activate the A/C compressor, I must toggle repeatedly between the A/C and Vent settings to get the compressor to eventually come on.

2) Once the A/C compressor is running, it stays running and does not switch on-and-off, as it should. I do not know which switch, e.g. A/C relay-hold switch on passenger side fender well or blower motor relay on the firewall driver's side, is responsible for allowing the A/C compressor to cycle on-and-off during operation of the A/C.

QUESTIONS:
1) Does anyone have thoughts, as I am having a hard time diagnosing the problem, even with the shop manual?? I have not replaced any parts.

2) The A/C relay-hold switch seems hard to find, but the blower motor relay appears readily available (unless I am missing an obvious source, which is likely)??

Thank you,
Jim Brooks
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Old September 9th, 2012, 08:37 AM
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Originally Posted by JBrooks View Post
1) I must move the dash switch repeatedly back-and-forth from Vent to Normal/AC to Recirculate before the A/C compressor will engage and come on.

Toggling the dash switch repeatedly will not turn the compressor off.

If I leave the dash switch in the Normal/AC or Recirculate position and turn off the engine, then the compressor and A/C will come on when I re-start the car.

If I move the dash switch to Vent, Heat, Defrost or Off and turn off the car, the compressor stays "off", when I restart the engine. To activate the A/C compressor, I must toggle repeatedly between the A/C and Vent settings to get the compressor to eventually come on.

Originally Posted by JBrooks View Post
2) Once the A/C compressor is running, it stays running and does not switch on-and-off, as it should. I do not know which switch, e.g. A/C relay-hold switch on passenger side fender well or blower motor relay on the firewall driver's side, is responsible for allowing the A/C compressor to cycle on-and-off during operation of the A/C.

As Bill Gates said: "It's not a bug, it's a feature"

You are describing normal operation in both cases.

The system is designed to run the compressor whenever it is switched to A/C, and to be able to run the compressor in Defrost if desired, by first switching to A/C, and then to Defrost, as you describe above.

The original A6 compressor with POA valve does not cycle.
The POA valve regulates the system pressure so that the compressor can run continuously.

- Eric
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Old September 9th, 2012, 12:07 PM
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Thank you, Eric.

I apologize if my first question was not clear, but I am wondering if someone can provide insight as to which switch may be at fault, e.g. I am having difficulty getting the A/C to switch on and I have to keep toggling the switch back-and-forth multiple times before the compressor will engage.

Similarly, I can not turn the A/C comprssor off with the dash switch. I must turn the engine completely off with the dash switch in the off position.

Any thoughts?

Thank you,
Jim
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Old September 9th, 2012, 01:26 PM
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Originally Posted by JBrooks View Post
Thank you, Eric.

I apologize if my first question was not clear, but I am wondering if someone can provide insight as to which switch may be at fault, e.g. I am having difficulty getting the A/C to switch on and I have to keep toggling the switch back-and-forth multiple times before the compressor will engage.

Similarly, I can not turn the A/C comprssor off with the dash switch. I must turn the engine completely off with the dash switch in the off position.

Any thoughts?

Thank you,
Jim
Jim,
The issue you describe about not being able to disable the compressor when the dash switch is moved out of AC is the normal function of your system, and yes it is a nuisance. Here is a thread I did about a year and a half ago that describes the function of this system and how to make it work better. Take a look at it and then feel free to ask any questions and I'll be glad to assist you. The Hold In Relay is located on the inside of the passenger side fender as shown in the attached photo. Your issue regarding the difficulty engaging the compresor may also be related to this relay.

Brian

https://classicoldsmobile.com/forums...-function.html
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Old September 9th, 2012, 02:12 PM
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Thank you, Brian.

This is awesome information, and I appreciate your connecting me to this thread.

Given that I have to work my dash switch repeatedly to get the compressor to turn on, I am guessing I need a new relay.

Does anyone know of a source for the Hold-On relays?

Thanks again,
Jim
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Old September 9th, 2012, 03:25 PM
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Originally Posted by JBrooks View Post
Thank you, Brian.

This is awesome information, and I appreciate your connecting me to this thread.

Given that I have to work my dash switch repeatedly to get the compressor to turn on, I am guessing I need a new relay.

Does anyone know of a source for the Hold-On relays?

Thanks again,
Jim
Jim, my suggestion is to first go through the testing I mentioned in the earlier thread before you start throwing money or parts at the problem. Do the testing to see where the problem lies. It could be as simple as a bad wire connection. Guessing can get expensive.
Brian
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