AC compressor power

[Dave C.]

I have an 85 with factory AC, which still works. I noticed that wherever the lever for the climate controls is positioned, the compressor is powered up, except in the off position. So if I have lever all the way over on the defrost, the AC is on. What should I look at?

 

[350runner]

It is designed that was as the when in defrost mode it removes humidity from the air

Sent from the dust in front of you!

 

[Dave C.]

Ok, I just found it odd that it is on all the time, except when the control is in the off position. For instance if I have the heat vents on, and the air lever to hot, and the AC compressor is running. Now I just need to find out why it's not building any pressure and making a lot of noise. My gut tells me I need a new compressor!

 

[350runner]

Oh I see Idk if it's the compressor. As you have per going to it at all times. Where's Jerry?

Sent from the dust in front of you!

 

[chengny]

For instance if I have the heat vents on, and the air lever to hot, and the AC compressor is running.

There should be no power available to the compressor when the selector lever is in OFF, HEAT or VENT. Function chart:

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In all positions (other than OFF, HEAT & VENT) it should be able to run - but that doesn't necessarily mean it is running all the time:

If the selector is in one of the COMP ON positions, power is constantly available up to the low pressure control switch. It is only when that switch closes - due to cooling requirements - that power is applied to the compressor clutch.

However, if the selector switch is in one of the COMP OFF positions, power should not even available to the low side control switch. Consequently, the compressor clutch can't ever pull in. So, if the compressor is running in the HEAT position for example, your selector switch is bad.

Now I just need to find out why it's not building any pressure and making a lot of noise.

If your system is very low on refrigerant - and even if the compressor is fine , no discharge pressure will be developed.

As far as making a lot of noise, you will have to be more specific. Is it squealing, knocking, grinding, etc?

 

[350runner]

Hey Jerry that chart shows it having power in Def mode.

Sent from the dust in front of you!

 

[chengny]

Yeah correct, and it agrees with what you say above.

When he notes:

So if I have lever all the way over on the defrost, the AC is on.

You reply:


It is designed that was as the when in defrost mode it removes humidity from the air

 

[Dave C.]

Thank you Jerry for the chart and application description. I recharged the system this spring after I found one of the lines had a pinhole. Proir to charging I flushed the system and found the oil to look like graphite, so I would assume I pushed the compressor by re-using it. The AC work all summer until recently. It's not building pressure, and that's when I noticed that the compressor is trying to run all the time. I'll have to check out those switches.