jjrbus

93 Toyota 3VZE auto dual rear wheels. I am on a trip with lap top I do not know how to use and a poor internet conncection. A Toyota Tech in Lake City or Gainsville or NW Florida would be good news!

AC comes on and works well. After about 20 minutes the blower (new)sound increases in volume but air coming out of dish vents slows and then stops. No amount of fiddeling with switch's and levers will get the cold air to come out. Stop,shut off engine and AC works well again when restarted, 20, 30 minutes down the road and air stops coming out. Must be in the heater vacuum lines or heater doors.

I was able to access the on line 93 FSM but do not find heater/ac vacuum lines in it?

Any input, links, videos or duct tape McGiver fix's greatly appreciated. Jim

scope103

Whew! That's a relief. Because there aren't any vacuum lines in the heater/ac (okay, the ac idle-up is vacuum, but that's almost certainly not your problem.)

Back in the stone age (1993), real men didn't rely on vacuum actuators. The doors moving your air around are all worked with push-pull wires directly to the controls. And your problem does sound like a loose air door moving on it's own. Here's a very abstract diagram of the system: http://web.archive.org/web/201102052.../4generald.pdf

I have no experience with a problem just like yours, so that's the end of my help. You might be able to see something (not) moving from underneath the dash, but I'm guessing you'll need to remove a good part of the dash to find the control wire that's disconnected.

Good luck, and tell us what you find.

jjrbus

Good luck, and tell us what you find.[/QUOTE]

I am always grateful for any input but even more-so now out here in the hot wilderness with sporadic AC!

I have basic tools and managed to get the glovebox out and confirmed the lack of vacuum lines. Not sure weather to be happy about it or not? Also look's like much of the dash will be coming out. Unless someone pipes up with quick fix.

I was unable to access the link you provided

Will be looking for a harbor freight parking lot to work on this and will report back when able. Many thanks Jim

jjrbus

I managed to get a couple pieces of the dash off and I do not see anything wrong, not that I know what to look for.
I stop at Advance Auto in Dothan AL and ask for a Toy Mech I am directed to A shop called Master Mechanic and told the guy is a long time Toyota tech.

Stop at shop and he looks over my RV AC and sees nothing wrong. Claims that it must be plugged with crap. I told him I had entire system apart converting to 134A, replaced all parts and cleaned everything and that it would work good for a short time and then stopped. He scratched his head and said it makes no sense. Thought about it a bit and decided that the system might be freezing up. He adjusted the switch up over the blower motor and said to give it try. (can't remember name of switch?)

He spent about 20 minutes on it and would not take any money, time will tell. Jim

Charchee

If I had to guess I'd say that you have a restriction in the evap coils. You could be freezing up (caused by low freon or restricted air flow due to clogged evap coils) or the evap box could be filling with water due to a plugged drain. In the first case you would hear more noise from the fan due to it blowing air up against a wall in that little box and in the other, the fan cage could be getting wet however I doubt this is the case. Check to make sure you have some water dripping from the passenger side around the rear of the front right fender. The ac in my 89 hadn't been used in 10 years because the PO owner didn't think it worked but after putting a new hose on it and charging it with some 134 and dye to test it, I found that it did work. In my excitement and distracted by counting several leaks I found, I didn't ever think about checking the drain. I went to vacuum it the other day and when I pulled out my rubber floor mat I found that I had water all in the floor pan.

Just wanted to give you a couple things to check.

scope103

That would be the "RPM" control on the A/C Amplifier.

Not really documented in the FSM, my best guess is that it sets an engine RPM below which the compressor disengages. http://forum.ih8mud.com/threads/expl...r-does.173016/

He did the right thing, not taking any money for it, because I don't think that will work.

I think Charchee is on to something here. Everybody wants the a/c to blow cold, so you want a REALLY cold evaporator, right? Well, you don't want the evaporator to get below freezing, because in any humidity (does it ever get humid in Florida?) the water will condense out of the air and freeze onto the coils. The system is designed so that the Thermal Expansion Valve (TXV) senses the temperature of the evaporator, and when it is "cold enough" it restricts the flow of refrigerant. If it stays cold, the pressure builds up, and the pressure valve shuts off the compressor, until the warm air going through the box warms up the evaporator.

Paradoxically, as Charchee points out having low freon will actually make the evaporator much colder than designed, and it might out-run the TXV and freeze up. Once covered in ice, no air can get through. I'm going to guess your mechanic at least put some gauges on, so that should have been caught.

I'm thinking it might be something else: if the temperature bulb of the TXV got knocked off the evaporator coils (you did say everything was "cleaned"), it would not properly sense the temperature of the coil, and it could get so cold that ice built up. Eventually, the ice would get deep enough to reach the bulb, the TXV would finally close, and stay closed because it's now encased in ice. The compressor would stop, but that hot Florida air would still be trying to get around the ice, and after a few minutes the ice would melt. Starting the cycle again.

How to tell? First, check that the compressor stops within 30 seconds or so of the change in fan noise. You might have to pull to the side of the road to pop the hood; DO remember to give it some gas in case the now-adjusted RPM control is shutting it off at idle. Once you're at the side of the road, look under the air box for a regular drip of water. All a/c systems drip water (it's the atmospheric humidity getting "dehumidified"), but if frozen up the drip might stop. If after a few minutes you get a good stream of water, then the A/C starts blowing cold, that could be the ice break-up (well, melting).

If you get no drip at all, as Charchee says you may have a soggy carpet. The drain line can get plugged with plain ole dirt, the evaporator box just fills with water, and no air can get through. Usually, that gives a gurgling sound, but eventually there is enough water to leak out and soak the carpet. That's an easy fix; get underneath and clean the drain.

jjrbus

Many thanks for the help. Freezing is the issue, cleaned drain, not dirty and flows freely, until frozen . Armed with the knowledge of what is wrong, I am able to juggle ac on and off and recirculate air and use AC. I will do this until I stop for a few days where I can work on AC. As I head north it becomes less of an issue.
Now headlights are acting up, hopefully I can fix without asking for help