hey mates,
i just purchased a 2004 roadster for a very good deal but the ac is not working. (133k miles)
the light comes on when I hit the ac button but there is nothing but hot air and the ac clutch does not engage.

here is what I have done
1) tried to refill freon but found the static pressure was about 100psi at approx 90 degrees outside. (indicating system is charged)
2) checked AC fuse (Not blown)
3) checked to make sure white ribbon was firmly plugged in to dash controls ( It was)
4) now I wanted to check the relay but im not sure which it is and i do not have a manual
5) the car had a cheap air filer on it and it had rubbed up against the cable that connects to the compressor harness. it had worn the outer casing but there is a single wire that does not appear damaged that plugs up to the compressor harness.

Does anyone have any suggestions from here? or do you know which of the relays in the following pic is the AC relay? thanks!

 

Got your message. Low side pres should be around the 38 - 45 mark and Hi side will be at 90 degrees somewhere around 200 - 250 PSI and with R134 which you have will sometimes hit as much as 350 PSI. R134 runs HOT and Heat equals pressure
With 133,000 miles you are due for a complete overhaul for max efficiency. This means...Possibly a Compressor, an exp valve. ALL new seals/O-rings and a Drier/Accumulator. Also best to replace the Low Press Switch. The system as always should be flushed reoiled then vacuum tested. If vacuum holds for 5 minutes replace the old Drier with the new one QUICKLY ( A new drier should NEVER be exposed to ambient humidity any longer than necessary) and then Vacuum for 30 - 45 minutes. Check once again for vacuum loss and if its holding--Recharge

Also check if you are getting power to the LP Switch on the HOT side. If so jump it and see if you are getting power to the clutch. There MUST be pressure in the system to activate the switch to power the clutch. Also....Is your engine cooling fan coming on when you turn on the A/C ? It should in order to cool the freon in the condenser. No cooly Freon means big bang because Hi side pressure will hit 500 PSI plus.

DONT let the compressor fail (Hence Replace---133,000 miles is a lot for a comp) cuz if it does it will gum up your system and you may have to replace Cond and Evaporator

 

thanks for the reply and help eazzy.

1) where exactly is the LP switch? I will test it for power
2) I have NOT noticed any fans engaging when i hit my AC button. what does this mean?
3) i found this picture of a nissan relay board (was from different model but appeared the same as the one in our 350z. It does not indicate an AC relay. is there not one?