My friend just bought a 90 LS400. The A/C is blowing warm air. LCD display is inop as well, but it still functions, A/C light comes on, you can turn the temp down and it beeps each time you press it (although you cant see what temp its actually at since the LCD is inop)

I don't hear or feel the compressor kicking on. I'm assuming its not coming on. I thought the A/c light was supposed to not come on or blink if the compressor doesnt come on?

I need to figure out if its a bad compressor or if its just low on refridgerant.

Here is how I was going to test. Let me know if this is OK to do.

Pull the wire going to the clutch and check for voltage. If there is voltage going to the compressor from the plug, then there is a problem with the compressor or the clutch.

If there is no voltage, that means the system is low on freon. Could I run 12v+ to the compressor at the plug and see if it kicks on, just to verify that th e compressor/clutch actually works? Will I damage anything if it just comes on for a second or 2?

Now, if I determine the system is low on freon, can I just buy a R134 retro kit, fill the system with freon and add a leak detector? The compressor should kick on when I start to pressurize the system correct?

The sight gauge wont tell me anything about the level of freon in the system if the compressor is not coming on, correct?

If get one of those coversion fittings, can I screw on a R134 gauge and accuratly read freon pressure using a 134 gauge?

Sorry about all the questions, I just want to make sure I'm doing this right.

If the pump isnt coming on, I'm not going to mess with it. Basically, if I have to open up the system and replace a component, I'm going to tell my friend to take it to a shop.

 

youre low on refrigerant.... most likely if its low and the clutch doesnt kick on, there is a lead somewhere... look at all the a/c lines for signs of a leak, or before you add freon, put some dye in the system so it will be easier to spot when or if it leaks out...

 

I found the high side pressure fitting, and pressed the center to see if any freon was pressurized in there, and just a little green goo dripped out, no pressure at all. I guess that means its low on freon?

 

I found the low pressure fitting on the passenger side near the firewall.

Also found out it had been previously converted to R134 but there was no sticker.

I put charged it up with some freon with leak dye, and she blows cold air now.

I ran it for about 20 minutes and its blowing nice cold air. Only problem now is I dont see any water coming from the evaporator. I guess I need to jack it up and crawl under there to try and find the drain hose.

Can anyone tell me where to look? I'm going to blow it out with some compressed air.

 

The drain should be on the passenger side, behind front passenger wheel and about a foot in from side of car.

Attached is a diagram. It's for a 1997 LS but might help.

Rob
'97 LS400