I own a 1990 240SX and I'm having a problem with the air-conditioner. Problem is, when I press the power button, I get nothing...no light or power to the air-conditioner motor. I have checked fuses in two locations (inside the car on the drivers side and under the hood on the passenger side). I would appreciate any assistance that anyone here could provide. Thanks.

Boris L. Ferrell
[email protected]


The A/C unit will not turn on at all if the pressure switch in the A/C unit detects low pressure. Make sure you have pressure in the system first. I don't have the same A/C system, so someone else will have to tell you how much pressure there should be when it's turned off (it may be about 60psi). You have to use an A/C pressure gauge.

[email protected]

Re. 2

OK heres the deal with 240sx compressors...if you have a leak or you have lost all of your freon you wont get anything...default there is a safty switch that if you have no freon it wont come on so you dont burn the clutch up on the air conditioner....have your freon level checked to see if you have a leak

[email protected]

Re. 3

I am currently having the same problem on my 89 240. The AC light comes on, the engine goes into a fast idle, but the air temperature remains the same. There is coolant in the system (I'm unsure if the PSI is correct, I had a friend check it), the relays have been replaced, all fuses are fine, however the AC clutch still doesn't  engage. Using a lead wire I can manually engage the clutch. The low pressure switch on the canister (next to the sight glass) is ok. Pin 41 on the E.C.U. reads the correct voltage with the AC switch on or off, but the volt readings from Pin 11 don't change like they are supposed to. Any ideas?

Vic - 89 240SX
[email protected]

Re. 4

Someone (don't recall who) was having problems with AC. Said that they could manually short it to get it to engage, but normally it didn't work even though all parts checked out. Could the acceleration cut control be stuck in the on setting. This is supposed to be a shutoff for the AC when under large throttle openings. If this is somehow being activated the AC  clutch should be disengaged I think. This is a signal coming from ECU to the air conditioner relay. Not sure what might cause this. Don't remember if you checked the AC relay or not. So relay is probably the first thing to check. If all that checks then either the ECU is telling the unit not to run, or you have a bad connection/harness. 

Good luck,

Shawn Clark
sd&[email protected]

Blower fan only works on high
So, your blower motor only operates on high or setting number 4?

There is a resistor for the S-13 located behind the glove box to the left of the blower motor that needs checking, assuming you checked the fuses first. Pull the harness off and check to see if continuity exists between each and every terminal. If it DOES NOT, the resistor needs replacing. This odd part is generally available at most junk yards, as the dealer charges a pretty penny for this thing.

Bill Bryant
Email: [email protected]

Why isn't my A/C turning on?

When I first got my 240, the A/C would act like it was turning on, but not actually produce any cold air. The switch worked, the light came on, the engine went into fast idle, but still nothing. I was working at an Audi dealership at the time, so on a free Saturday, I decided to do some investigation. First, I purged the system and refilled it (yeah, I ripped off some freon...shhhh) and that didn't do it. Man, did that suck. I just figured the system was empty, and now I'm thinking that the compressor is frozen. One of the mechanics there wasn't busy, so I had him look at it. He fiddled with some of the connectors, and hooked up a voltage testor (I had already checked the relay). He soon found that the temperature activated ground cut was the culprit (the  little brass nut-looking thing with 2 wires coming out of it...one has a connector, the other screws to a ground). New part at Nissan was somewhere around 20 bucks. The dude at Nissan told me that I would have to pu! rge the system AGAIN to swap the part. So, I did, but upon taking out the sensor, I found that the advice was COMPLETELY WRONG.  Just swap the part, and away you go. I think Nissan has bad luck with ground circuits, I'm checking those first from now on.  Happy Honda Hunting!

Eric Johnson
Email: [email protected]