pdpunome

08 rdx here. Have an issue with a/c compressor and condenser fan not turning on. I replaced relays with lates 05 verson no luck. I have a lisle relay tester and if I jump the high amp legs of the relay then I can get the compressor and fan to kick on. Testing the other two pins on the relay I show 0vdc when ignition is off and both show 12vdc+ when iginition is on. So need to know is that correct? I would think one pin would need to be ground but this is the case on both the compressor and fan relay terminals. I replaced the a/c line pressure transducer hoping that was causing whatever is going on to not trigger it but no luck. I also have a high end fancy scanner which I can manually turn on the clutch and fans to test and that works so tells me that the dash switch and ecm/pcm can send the command. Something electrical is going on and I need some tips.... first is the relay suppose to get two + voltages to then charge up the relay to click and send the + volts through? if not then what is causing the short?

01acls

You need to explain your testing better. Also was your tests done with the relay installed, removed, ignition and/or Climate Control on or off, etc?

With the ignition on and Climate Control in off position... Trigger side of the relay...
This is how the relays should be. With both fan and clutch relays in place, key on, the trigger side of the relay is hot. Note... The climate control is the negative switch... Completes the circuit when turn on by grounding the hot trigger wire to trigger the relay (to power the clutch or fan).

Same as above but with relay removed...
Trigger side of relay is hot on one side only and open (neither hot or grounded) on the corresponding side (testing trigger side only).

With the ignition on or off and Climate Control in off position...
Power or load side of the relay is hot on one side only with or without relay in place.

pdpunome

I tested the dash switches as well since I have a backup set. Still no dice. Testing the relays with the lisle relay tester tool which plugs in the spot of the relay then the relay into it. It has jumper post/test terminals this way you can test the relay and the relay socket. IGNITION OFF - testing with dmm to body ground: The two larger legs of the relay are the + volts to the part being powered which I have + volts on one and zero on the other. the smaller two terminals read 0 volts. IGNITION ON AND A/C SWITCH MODE ON - testing with dmm to body ground: same larger terminal that had + volts remains true, other large terminal does not. The two smaller side terminals both read + volts. These test results are both on the compressor relay and condenser fan relay in which both are not operating. Now if I jump the two larger terminals of the relay sockets it does run and can get both the fan and compressor to turn on. Dead clutch or fan has been ruled out. Dash switches have been ruled out. Blown fuses have been ruled out. Relays have been ruled out (I have 12 total I have been testing with). Pressure Transducer Switch ruled out, replaced with new. Something is not allowing these to turn on out of nowhere.

01acls

You've only ask about testing the relays. What exactly is wrong with the climate control and what are the symptoms?

The climate control has a self diagnostic feature. Have you try that?
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pdpunome

I laid out what is wrong... ruled out alot of potential causes so need further direction especially why each relay is getting two + feeds instead of a + and -

01acls

Your problem is not in the relays. Relays are suppose to have two hots. One to trigger the relay the other to power the fan or clutch. That's perfectly normal.

Your problem is why isn't the trigger hot being grounded to trigger the relay(s).

Possible items are ECM not trigging the relays (defective ecm) or ECM is not receiving data from climate control to trigger the relays (grounding).

If it's the latter then the climate control is not receiving the right signals from the ac system's components.

So again what is your climate control doing or not doing and when?

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