AC randomly struggles at low speed and stop/start

[irowiki]

So the air conditioning on Party works pretty well, at highway speed. When it's 80-90 F out it gets down into the high 40's F which sure beats 100+ F.

Now, if I've had a long highway stretch then do some stoplights, the AC still works fine.

If I start up at my house and everything down there is hot (meaning, got home from work, sat 15 minutes, then go out again) which means stop signs and stop lights right away, the AC only wants to get to 60-70 F until I get on the highway, then it stabilizes after a bit.

My first thought is to clean the condenser out real good, there's even some sort of spray cleaner for it. Any other ideas? I'm more AC savvy than I used to be, but still need to larn me some stuff!

[mrdance123]

The electric condenser cooling fan is missing, or it does not turn on?

[irowiki]

Oh the fan is there and it turns on, the system just seems like it doesn't want to work too well above 90F.

[mrdance123]

Maybe the AC switch is half broke, only the 'econo' level works?
Is the hot water shutoff stuck or leaking, letting hot water into heater,
possibly combined with the hot air blend door not completely closing?

There are 2 adjustment dials on the amplifier circuit board,
next to the fan blower motor behind glove box.
One sets the minimum RPM necessary to turn on compressor,
it might be turning off at idle if not set properly.
The other turns off compressor when air gets cold enough, before the evaporator clogs with ice.

I've never measured my cold air temp, but now I'm going to.
Maybe these cars were designed for the outlawed R12?
Been converted to 134, becoming less efficient?

[irowiki]

Econo and full AC works, I've tested both. Econo is great for mornings when you only want a bit of AC.

I will check the hot water shutoff and the blend doors.

Funny, on the amp board, both dials are covered with labels, Toyota didn't want you messing with it by 87 I guess? I also need to check the vacuum switch.

It also doesn't help the car is dark brown and heats up super hot. One day it was 150 in the car when I got in it after work!

I might try the hose trick, apparently you can pour water on the condenser while the engine is running to get an idea of performance. I still need to clean the condenser too.

They were definitely designed for R12, and R134 hurts them. On my 92 Camry, it was designed for 12, but they knew about 134 coming in 2 years so they designed it for both I guess, after converting it, it works like a champ.

[teranfirbt]

If it's the original R12 charge it probably has leaked enough out that it is low on charge. You can still get R12, but it's a little spendy and you have to know someone with a license for HVAC work. I'll be trying out Envirosafe in my system (it's a blend of propane and Isobutane that acts like R12). Legally it's only good to go into R134a systems, but if you put the right fittings on you've essentially converted, so you should be ok to put it straight in. They say you can mix it with R12, but it's probably not the best. I'll update once I have a chance to get some testing done in the next week or so.

If you really want to know what's going on you need to hook up a set of gauges and look at high and low side pressures. Depending on outside temp, high side should read around 200 psi at 1500 rpm, low side should come down to around 28-30. If the low side comes down to 20 and then bounces back up to 30 it means your expansion valve works but your charge is low.

[irowiki]

It has been converted to 134.

Unfortunately the people who converted it (Midas) put the fittings on the wrong sides so I can't check it with my manifold set.

If push comes to shove I'll take it somewhere else and have them fix the fittings.

[teranfirbt]

In that case it's probably just low on charge. R134a molecules are smaller than R12 and will slowly seep out through the stock rubber hoses. Over the course of a year or 2 you'll lose enough to reduce the effectiveness.

[mrdance123]

AC performance, Speedy Blue T4, vent on recycle.
When we have a serious heat wave I'll do this again.
Before this testing, I moved the amplifier temp setting,
from the half way point (up or down) where I found it,
to 3/4 of the way to clockwise coldest setting.

Weather AC Fan Vent Drive Compressor
Temp Humidity Level Speed Temp Status Run-time
85 ?? Econo 4/4 48-50 highway 40%
82 ?? Max 4/4 39-41 highway 75%