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I have a 02 EX 1.7L and the AC doesn't work. I'm already planning on changing both the high and low pressure lines since I found a leak. My problem is that whenever I turn the blower motor on the light for the AC button on the console lights up and matter how many times I press it, the light never goes off. Any ideas if there could be another issue, say with the AC switch of the compressor itself that I should look into. I've check the relay and the relay works fine.
So I've filled the system the 134a with UV dye and had to jump the relay to engage the clutch. After I filled the system and put the relay (which I know works) back into its slot the compressor clutch still won't engage. My next step to the check the pressure switch and receiver drier. But I notice that the condenser fan doesn't kick on. Could this be due to an issue with the pressure switch if that is the faulty part?
If you think a good mechanic is expensive, try hiring a bad one
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From: Midwest. Aiming about mid-chest
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Re: AC Troubleshooting
Compressor won't engage. Do both radiator fans kick on when you turn the AC on? (very important diag observation)
IF NO FANS
Ohm check thermal protector on the compressor. Should be continuity
Unplug pressure switch. Ohm check switch. Should be continuity
Connect a grounded jumper wire to each of the terminals in the harness connector from that pressure switch (engine running). (I don't know which wire will make it kick the compressor relay on, but one of them should)
Does that make the AC kick on?
Report back with the results so I can figure out next step
or search the forum for any of the 10,000+ AC diag help posts I've made
There is continuity at the thermal protector and at the pressure switch. Jumping the pressure switch does not turn the compressor on. Compressor will only activate if I jump it at the relay.
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 517
Re: AC Troubleshooting
Connect a grounded jumper wire to each of the terminals in the harness connector from the pressure switch (engine running).
Do NOT jump the connector with a paper clip.
I want a wire connected to ground clamp on the battery, touch that wire to each of the terminals in the pressure switch harness connector.
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 517
Re: AC Troubleshooting
Does the car have other odd electrical issues going on?
Door ajar/key beeper does not work?
The "you left your headlights on" reminder beeper does not work?
Warning lights on?
Courtesy lights don't work?
At least one function for wipers does not work?
The brake light stays on even though the the dot-3 is topped off and I did the brakes. It's been on since I bought the car. And the first setting of the wipers (lowest setting) doesn't work. Everything does.
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 517
Re: AC Troubleshooting
Originally Posted by Chachski90
The brake light stays on even though the the dot-3 is topped off and I did the brakes. It's been on since I bought the car. And the first setting of the wipers (lowest setting) doesn't work. Everything does.
Search for info on troubleshooting the multiplex system (also called multiplex control unit, or MICU). It's now the prime suspect.
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 517
Re: AC Troubleshooting
The MICU is built into the underdash fuse box. In the wire diagram I posted it's the unit (box) that is between the wires you were checking and the PCM.
HVAC system AC request is made by grounding one wire, and that has to pass through the pressure switch and thermal protector, and then it has to go all the way to the MICU..
The MICU converts that grounded wire signal into computer data and sends that data to the PCM,
The PCM then controls the clutch and fans.
MICU is pretty much used as a body systems control unit. There's a lot of stuff connected to it, and they do fail.
Connect a grounded jumper wire to each of the terminals in the harness connector from the pressure switch (engine running).
Do NOT jump the connector with a paper clip.
I want a wire connected to ground clamp on the battery, touch that wire to each of the terminals in the pressure switch harness connector.
Hi, I know this is an older post, but I'm having this same issue, and havent found an answer elsewhere. I connected my test light to the negative battery terminal, and when I touched the pressure switch connector, one of them kicked the compressor and fan on. Does this mean that I have a bad pressure switch? The economy being what it is, I dont want to throw unnecessary parts at it, so any help would be very appreciated. Specs on my car are essentially the same as OP.
The switch should be closed as long as there is at least 28 psi. If you're sure it is properly filled then use a multimeter to measure resistance across the two pins on the low pressure switch. You should see continuity. If not, the switch is faulty.
