94 Ls 400

Larry W · October 22, 2010

I just had a new evaporator, dryer, and compressor w/clutch installed on my car. I noticed in our hot Florida weather that the a/c was not quite cold enough to the touch coming out of the vents. I did notice that the a/c is colder coming out of the driver's side and middle vents, but slightly warmer on the passsenger side and rear passenger vents. Am I just a little low on freon? Could it be that simple? Any advice would help. Thanks in advance.

AndyLowe · October 23, 2010

I just had a new evaporator, dryer, and compressor w/clutch installed on my car. I noticed in our hot Florida weather that the a/c was not quite cold enough to the touch coming out of the vents. I did notice that the a/c is colder coming out of the driver's side and middle vents, but slightly warmer on the passsenger side and rear passenger vents. Am I just a little low on freon? Could it be that simple? Any advice would help. Thanks in advance.

Hello Larry,

It sounds like your level of charge might be a tad low. Here's how to see without any tools:

- With engine off open your hood.

- Just Above and at the top, center most corner of your passenger headlight, you will find a Sight Glass.

- Wipe it clean with your finger and a little rag.

This Sight Glass gives you an inside view of the level of charge in your High Pressure Side, LIQUID LINE

You see a clear glass, without any "grayish milkshake" bubbles/vapor and liquid passing by. It should be completely clear, with engine off.

Now, start up the engine, turn on the A/C, open both front windows (you're creating work for the A/C) and go look at that Sight Glass again.

You should see a few bubbles/vapors (a grayish milkshake) flowing by, and then it should settle down to a completely clear Sight Glass, just like it was when the engine was off.

If you see the grayish milkshake going by, you are low on charge and need more freon added.

If you see a completely clear Sight Glass, use your hand to touch the larger metal tubing pipe, just under the black plastic cover, in the passenger side Hood Hinge area. It's down along the firewall and it is where the Service Cap is located on the Low Side Service Port.

This pipe should be very cold and sweating, due to the humid air condensing on it's 36 degree f internal temp.

If it is not sweating, after ten minutes of A/C system on, you are probably NOT at the correct level of charge and need more freon.

Toyotas and Lexus give us the Sight Glass to assist in knowing for sure. Many other manufacturers quit installing this excellent tool and there are many people attempting to service an A/C system who truly don't understand them.

If your Low Side Lines are sweating fine, along with the Sight Glass being Clear, I would think your system is properly charged.

Make sure there is water dripping from the evaporator case, just below the glove box area. It is the result of humid air condensing on the Evaporator Coil and falling to the bottom of the Evaporator Case. It should be dripping.

If its not dripping, clear its drain tube. (Rubber tube near passenger side catalytic converter)

Make sure your cap is on your Service Port! The cap has a rubber seal within as 90 percent of all schrader valves leak. (That's the valve core, just like your tire)

Andy