'03 Sienna A/C

High side or low side pressure? What is the ambient temperature? Pressure obviously is different between the high and low side, and will vary with ambient temperature.

My apologies for leaving out that detail---low side. 80deg Ambient.

With the engine at approx. 1500 RPM, blower speed at high, temp set to max cold, I think low side pressure should be somewhere between 21 and 35 PSI.

Your Toyota dealer who has the proper tools and experience to fix the truck correctly.

Jeff

I only go to dealers when I feel like getting over charged. As an engineer, I like to diagnose and fix (if possible) the problem myself. Today's mechanics (not all but most) don't know how to diagnose. Meanwhile they're happy to charge you a $80-$100/hr while they screw around. I prefer to educate myself, and if I MUST go to the dealer, equip myslef with an understanding of the problem so I can point them in the right direction.

Is there a problem with the AC and if so, what is the problem?

The problem was at an idle I wasn't getting any cooling. The sytem would povide some cooling (not much) as I drove the vehicle. The low side pressure was reading a bit under 25psi; so I was told that it needed coolant. I purchased some from a local auto store and charged the system until I was getting a low side pressure of around 35psi. The a/c now works and not a day too soon: the weather forecast for tomorrow is 95 and humid!!

I surmise that I must have a leak in the system, which isn't great news. I am to understand that repairing a/c systems on the sienna can add up quickly. I'll monitor the pressure to get some idea of how bad the leak is. I bought the van used 2.5yrs ago. The first two summers the a/c worked great; but this summer it started to give me problems.

It sounds like you have a very slow leak - it probably took 4 years to lose the little bit that you lost. An easier way to get an idea of the refrigerant charge (coolant is used in the engine cooling system - radiator, heater, etc.) is to look at the sight glass on the receiver drier. The receiver drier is a cylinder mounted vertically in front of the condenser, which looks like the radiator and is mounted in front of the radiator. There will be refrigerant lines leading into the receiver drier, and on top is a dime-sized glass window. When the AC is running, it should look like water flowing past the window. If you see foam flowing past, then the system needs to be re-charged.

I am not a fan of those do-it-yourself small re-charging systems because it is very difficult to monitor how much refrigerant is actually in the system. The correct procedure is to evacuate the system and then re-charge with a measured amount of refrigerant.

At this point, I would just monitor AC performance and if it needs re-charging more than once a year, have the leak chased down.

Ray,

Thank you for the time you have put in to respond to my post. I also thank you for correcting me on "coolant" vs. "refigerant"! :)

Take care, Rob

You're very welcome! Let us know if you have any other issues, we'll try to help out!

BTW, if you use incorrect terminology, the folks at the service dept might be a little less likely to take your suggestions seriously :-)

I agree with Ray O's diagnosis of a slow leak. If you don't have a leak sensor, a possible fix that costs you only your time would be to check each fitting to be certain that it is tight. You would be surprised after many temperature cycles that they can become loose.