Rudee023

Is there a pressure switch or something that only allows the fans to turn on when theit is refrigerant in the sytem? I know my compressor is toast (confirmed by shop) and I have zero refrigerant in the system but should the fans still turn on when I hit the AC button?

tenchu

I'd also like to know. I actually just got my AC working today, but the fans do not turn on

Rudee023

Just read there IS a low pressure switch that keeps the compressor from kicking on. So I'm guessing if the compressor isn't on, the fans wont come on.

tenchu

Theres a relay in the engine bay fuse box that will not allow the compressor clutch to engage if the car is low on refrigerant, you can bypass the relay to see if the compressor will engage. I took my car to an A/C shop yesterday, and they told me the car had an electrical issue that wasn't allowing the compressor clutch to engage, I took it home this morning, bypassed the relay, compressor kicked on, so I charged the lines (they were almost empty) and now the AC blows ice cold. I didn't have it on very long, but the fans didn't kick on, I hope they are good.

91LS400vgb

Correct - if the compressor doesn't engage, then the fans will not kick on;

Also, if I recall, on my 91 LS, the fans aren't on 100% of the time when my compressor is engaged, though I do see them go on some of the time.

Lexozz

No compressor, no freon, no A/C the fans will not come on.

The relay fuse is probably gone. I know for a fact the 95-00 has 2, one in the engine bay for power and the other for A/C fan speed regulation which is located under the driver side headlight. Once you turn on that A/C the fan should spin regardless as far as I know.

JAndersson

For the first gen LS400 the pressure in the AC system has to be more then 1323 kPa (13.5 kg/cm2 or 192 psi) for the AC fans to start turning at low speed (there is a high pressure switch in the system). The fans will also start turning at high speed when the engine coolant temperature becomes more than about 90° C (194° F).