A/c hell!!!
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Driver School Candidate
Joined: Jun 2015
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From: FL
A/c hell!!!
My new/used 95 sc400 has no a/c. I've done what I though was all the troubleshooting steps and am totally confused now. No codes during diag, clutch not engaging, jumped the relay and the clutch engages, checked refrigerant and was low so I filled it to the top of the blue, took jumper out and put relay back in aaaaaannnnndddd........no a/c. Wth? What am I missing? With it jumped I get ice cold a/c. Where is this elusive low pressure switch. I found the hps and it has juice but does nothing if I jump it. It's getting towards full summer and it's florida. I need some a/c...... HALP!!!
I have search but the word ac and switch and low are apparently way too common
I have search but the word ac and switch and low are apparently way too common
Last edited by Jax4litre; Jun 17, 2015 at 05:34 PM.
Thread Starter
Driver School Candidate
Joined: Jun 2015
Posts: 8
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From: FL
The ac works when turned on and the relay jumped. Wouldn't that mean the wiring was ok? I can see the high pressure on the passenger side. The High AND Low Service Ports The Relays For Climate Control The The One For defrost. Just replaced the relay and that didn't work. Was sitting in the car today at lunch and ran it it for a full hour with the relay jumped and the ac blew freezing cold. What else is there? All the mechanical components seem to be working fine. The high pressure switch doesn't do anything if I jump it, and all the functons on the ac control panel work. I dunno what else could be the issue
look for the pressure switch on the ac lines. Usually on the front, near the condenser on most cars. A faulty pressure switch can cause the clutch to not engage. These rarely go bad but it is possible. It is possible to jump / bypass the switch to see if the clutch engages. I am not exactly sure / do not remember which wires exactly to jump to do this.
Edit: just saw your last post of jumping the pressure switch.
Edit: just saw your last post of jumping the pressure switch.
Thread Starter
Driver School Candidate
Joined: Jun 2015
Posts: 8
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From: FL
Where is the ac low pressure switch? I see all the other components and thats the only thing I can't find.
Will it hurt the compressor if I just put a fusible link where the relay goes?
Will it hurt the compressor if I just put a fusible link where the relay goes?
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From: Wa
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Joined: Jun 2015
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From: Wa
Sorry, didn't see this part. Since the relay is new and when you jump it, the system works, then the problem should be before the relay, What is telling the relay to switch? I have not got my wiring diagram book for the SC yet, it is still on order. If you have one, then look for what is before the relay in the circuit.
I have a 300 but had the same problem recently. I relocated my fuse box to the trunk so the wires are super easy for me to get to. But basically, I was getting 12 volts up to the relay when I powered the a/c on, but only .11 volts on the other side of the switch, the one that goes to the compressor clutch. Turns out there are 2 wires on that "mg clutch" relay. Both are blue but one goes to the a/c controller on the dashboard. It ended up being shorted out to ground. So I cut that blue wire that goes to the controller and my a/c was finally working at 12 volts. Hope this helps.
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