Why won't the AC turn on in my '86?

[H8PVMNT]

I have been seting up an '86 Toyota for a bush work truck for my appraisal work in the middle of nowhere out here in eastern Montana. It has 2 lockers, 5.29s, BJ spacers and a mix of OME and Downey components and even some really beefy heim joint steering that I gave away a few years ago. Everything is turning out great... I need to run a laptop and printer in there for work, so I can't have dust billowing in the windows. The AC must be resurected!

Here's my issue:

1) The compressor/clutch thingy locks up when I jump it on the battery, so it seems to work.

2) The AC switch in the dash lights up when you push it, so I assume the switch works.

3) The switch, however, does not turn on the compressor/clutch thingy when you turn it on.

Is there a relay buried in there somwhere? I checked all visible fuses, and there isn't any blown. I must be missing something.

Any help is greatly appreciated! Three beers to whoever figures this one out!

 

[trucruiser]

I Think there is a sensor that prevents it from kicking on if you dont have enough refrigerant.
Do you know if you need a recharge?

 

[WristPin]

right. a thermistor/pressure switch.
plus the fan has to be in the on mode. does the fan work in all positions?
does the A/C light up?

here are the steps that turn on the compressor:

IGN SW ON
Blower switch on -> heater relay on ( blower motor run)
A/C SW on -> A/C amplifier ON (A/C Amp main power supply)
Low pressure SW on. Kicks on when refrigerant is above 30lbs
Thermistor supplies signal of evaporator to A/C amplifier
VSV On -> E/G Idle up
Magnetic Clutch on

you can use a tire pressure gauge to test pressure on the LOW side. this would be the first diagnostic step. needs to be at least 30lbs

then remove the glovebox. a harnes runsr along the HVAC unit on the upper right side. there is a connector that you disconect. has 6 terminals. and four wires. two upper terminals that are apart from each other. and four on the bottom. the bottom two have wires on the two inside terminals.

there should be continuity between the Red/green wire and blue/yellow wire. basically the two wires on the one half of the harness. this checks the pressure switch. it should be closed inorder for it all to work.

on the other side of the harness, is a yellow/green and white wires. this side is for the thermistor. resistance should be 1500 ohms at 77 degrees F.
resistance goes lower if its hotter than 77 degrees out.

there is also VSV diagnostics. but report back with your findings





remember that truck uses R-12. and compared to the new stuff, R-134a, its is not as good.
not as good molecularly and effciency wise. R-12 molecules are small so they leak easier. and its about 60-80 dollars a pound. i can get R-134a for 3 dollars a pound.

i am not saying that it sucks, just that once its all used up and or leaked out, you need to retrofit it with R-134a.

My 86 4Runner still works.

 

[H8PVMNT]

Yes indeed! I went to Oregon last week and my really hardcore buddy had once put AC in his 83 pickup. It took him a week to figure out about the preasure sensative switch that doesn't allow the compessor to turn on if there is no refidgerant.

By the way, I used one of those $29 R134 kits from walmart on a celica and it worked great! Thanks for the help.

I'll wait a while to fix the AC though because the friggin' thing spun a rod bearing about a week ago and I have to tear it down and find a good bottom end! Oh well...

 

[CJF]

When you get to fixing the A/C, please don't just throw r134 in it; that's a good way to destroy it. (Yeah, yeah, I know:"But I/my buddy put some in my/his Celica/whatever and...")

At the very least, use Freeze12, which seems to be gaining consenseus as an r12 compatible refrigerant.

Curtis