A/C doesn't seem to blow cool at idle, while driving it blows cold

Today I had the system evacuated and converted to 134. At first the compressor didn't kick on and the techs were thinking it was an electrical issue. Turns out, when the tech pulled it off of the lift and drove it a little, some divine intervention happened and it started to blow cold. I only have speeds 3 and 4 of the blower speeds working so tomorrow I will go to the junkyard and fetch a resistor from a previa. I noticed that the ac doesn't blow cold while at a stop, but when the engine becomes under load, i hear a click in the pass side dash area and then it starts to blow colder. Do you know what this is? Is something going bad? Also, my rear a/c isn't blowing and it seems that the slide knobs to turn the temp "blue"(left) doesn't want to go all the way...like maybe something is binding? I'm pretty sure it is happening to the other sliding knob too.

Hi & welcome to TVT. There is a little plastic box with a small knob on it that hangs down under the dash (over by the glove box). That box is your "AC Amplifier". The knob is to adjust the RPM at which the compressor will kick-on. Toyota did this because these vans have a problem circulating enough air for the AC at idle. It gives you the option to set the AC so it won't kick-on until you are at higher than idle. If however you wish for it to kick-on at idle, you can adjust that knob to make it happen. That's the way I have mine set up, but it's important to watch the temp gauge while sitting at an idle in heavy traffic or in a parking lot. Even if your cooling system is working correctly it's likely you'll overheat the engine if you sit in one place for too long with the AC on at idle.

These vans are notorious for having problems with the heater controls. Toyota used poorly designed control cables. They are single strand metal wires inside plastic sleeves. As they wear the metal wire digs into the sleeve (typically at the bends) and begins to bind. This can be temporarily remedied by putting a penetrating lube inside the cable sleeves. WD-40 will work, but a higher quality lube like Tri-Flow will work better and last longer (probably 1 - 2 years). Eventually the same problem will reoccur. Toyota did redesign the front cables after the fact (sometime after 1989), but there are only a couple of these that are still available. Also, they will not work on the pre-89 heater control spiders..............and 89 spiders are NLA. Tim

Thanks Tim for your help!! I went ahead and ordered the correct front blower resistor and will be installing that later this week. As far as the rear ac is concerned...I ended up cleaning the condenser due to it being clogged up by hair and debris. After that, I opened the access panel and decided to pound on the blower. To my delight, it started working and now I have both front and rear ac working!! I am falling more in love with this van each day! The only two things I haven't checked to see if it is working is the windshield washer squirters and the cruise control.