98 GS still burns too much gas w/ AC Running

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handogg - 24 Jun 2006 09:42 GMT

The car gets its usual mpg of 20 as long as the AC isn't running. With
the AC running, I get something like 12-15 MPG.

I've looked for the sight glass which may help me diagnose further but
I can't seem to find it. I also have the encyclopedia-type repair
manual from lexus. The book tells me what different types of things to
look for in the sight glass but I can't find it in the first place!!!

Also the cooling fan is always on if the AC is on and the car isn't
moving. The cooling fan will go off if I turn off the AC

What is it about a faulty AC that burns up so much gas?

HELP!! Thanks :)

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Ray O - 24 Jun 2006 23:08 GMT

> The car gets its usual mpg of 20 as long as the AC isn't running. With
> the AC running, I get something like 12-15 MPG.
[quoted text clipped - 10 lines]
>
> HELP!! Thanks :)

The sight glass should be on top of the receiver-drier. The receiver-drier
is a (usually silver) cylinder about the diameter of a can of soup but about
twice as tall, usually mounted in front of the condenser and radiator,
behind the front grille.

It is OK if the cooling fan comes on and off with the AC. A partially
discharged AC will run more often and will use more fuel, but it shouldn't
use as much fuel as you're experiencing. It is possible that there is an
internal problem with the compressor but normally the belt will slip and you
will hear squealing and the AC light will flash.

Another component of the AC is an idle-up circuit that increases engine RPM
when the AC compressor is engaged. When the AC is engaged, engine idle RPM
should increase about 100 - 200 RPM.

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Ray O
(correct punctuation to reply)

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