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Old 06-15-2021, 11:37 PM   #1
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Default Low Pressure Switch question

So I jumped the low pressure switch to see if that was a bad connection and when I did I heard what sounded like a ticking noise by the relays. Only made that noise when i jumped it. Would that mean it's a bad relay?
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Old 06-16-2021, 12:44 AM   #2
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Relay theory tells me that when a relay is energized, power applied to energize the coil to pull the movable contact, it is considered a good working part. In theory, solenoids work in pretty much the same manner.

So the clicking of relays is a good thing...

Which system are you testing with the Low Pressure Switch?
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Old 06-16-2021, 12:53 AM   #3
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Originally Posted by PorknBeans View Post
Relay theory tells me that when a relay is energized, power applied to energize the coil to pull the movable contact, it is considered a good working part. In theory, solenoids work in pretty much the same manner.

So the clicking of relays is a good thing...

Which system are you testing with the Low Pressure Switch?
Im trying to figure out why the compressor isn't getting power. I have jumped that and it turns on, but only that way.
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Old 06-16-2021, 04:41 AM   #4
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The contact points of the movable contact might have had arcing or carbon build up. Thus creating high resistance at that point(s).
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Old 06-16-2021, 01:43 PM   #5
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What are your AC system pressures? R134a conversion or still R-12?
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Old 06-16-2021, 02:34 PM   #6
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What are your AC system pressures? R134a conversion or still R-12?
Not sure yet I will have to check when I get back home. I had made an attempt last week to figure it out. When I thought I had it I put in a full can of 134 (it has been converted but its got an S13 compressor. When the compressor didn't kick on I stopped there.
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Old 06-16-2021, 06:57 PM   #7
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What are your AC system pressures? R134a conversion or still R-12?
Ok I got the pressures. Low side was 95 and high side was 99-100.
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Old 06-17-2021, 01:47 PM   #8
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Ok I got the pressures. Low side was 95 and high side was 99-100.

That should definitely be high enough to close/complete circuit of the low pressure switch. If jumping that switch manually causes anything "new" to happen, sounds like a bad switch.


With the connectors to the switch removed, the witch can be tested for closure using an ohmmeter.
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Old 06-17-2021, 08:28 PM   #9
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That should definitely be high enough to close/complete circuit of the low pressure switch. If jumping that switch manually causes anything "new" to happen, sounds like a bad switch.


With the connectors to the switch removed, the witch can be tested for closure using an ohmmeter.
I did try to jump the switch the other night and i was getting what sounded like the relay turning off and on rapidly.
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Old 06-17-2021, 09:12 PM   #10
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If the relay is turning on/off rapidly with power supplied to it. That tells me that high resistance is present and when that resistance is overcome. It allows the relay to operate. In your case…operating on/off rapidly. So that’s what I believe is happening here because with all of the other tests/assessments proving to check out good. It appears to be the relay failing. Also know that the relay is an electrical control point too. When power is applied, it will allow other components to operate with their needed current draw. Relays are called “K1” in schematics. Other relays would be called “K2”, “K3” & so on.
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