LJ78 Air Conditioning Repair? (1 Viewer)

[GTSSportCoupe]

Thanks for the post Nick, I had been wondering how hard it would be to recharge it meself. I have to get mine re-charged every second season.

You're welcome. Yeah, my system has some very slow leaks too. I end up recharging it every couple years too.

How does your A/C work when you're idling? Mine sucks pretty bad when idling, but is good enough while on the highway. I'm just assuming its related to airflow through the condenser, but maybe I've got more issues than that....?

 

[Jim from Idaho]

This is my final bugaboo to solve on my LJ78. Let's go back to the switch. How can I tell if it works? An just how exactly does one apply 12V current to the condenser? Can I do that with something as simple as a test light and ground wire? I took the truck in to the only shop in Boise that still works with freon. A pressure test was positive, no leaks, enough freon, but just no signal to the A/C to start up. Since I didn't have a clear enough copy of the A/C wiring diagram, they gave it back to me unchanged. I can't hear any "Click" from the rheostat, but then again my hearing isn't what it was.

 

[jblueridge]

in the engine compartment at the compressor there is a single wire. When that wire gets juice, it activates a strong solenoid that makes the clutch engage.
You need to disconnect the clutch wire from the wiring harness; there's a plastic clip.
Then with a spade connector or alligator clip connect the compressor clutch wire right to the battery.
When the engine is running you'll see the compressor spinning (hopefully).
Don't let this test wire get wrapped up in the running engine belts.

 

[Jim from Idaho]

Thanks! No luck when I hotwire the compressor to the battery. At least, I don't see or hear anything different from the compressor. The belt going to the compressor (and clutch?) spins all the time, so since I am such a newb I might not know what I should see spinning.

 

[jblueridge]

Jim, When you play with "hot wiring" the compressor clutch, you need to stand where you can see the front of the compressor pulley. When the clutch is not engaged the front of the pulley does not spin; the opposite is true when the clutch works. The engine should also change sound or even rev faster to compensate for the extra work of making the compressor go around.
If the entire pulley does not whirl around when the clutch is connected to the positive battery terminal, I would bet the clutch is dead. You could check phone book or internet listings for Auto Electrical repair shops that specialize in alternators, starters, etc. They could perhaps repair the electric clutch.

I bought a new compressor from http://www.coolstreamac.com/ They seem to know our vehicles.
I gave them this compressor info: Toyota replacement compressor is part number 88320-01011-84, a Denso 10P15C.
I was lucky enough to find a very good auto a/c place near here that is going to refill my system with original R12 refrigerant.

Eden, in the system there is a thermistor that changes its electrical resistance in response to temperature. From the BJ74 diagrams, it seems this electrical item is near the evaporator core, probably sealed up with it in its drip-catching plastic box. I would bet that thing is your problem.

 

[fiery1]

1. If to turn on the a/c is done via a rheostat switch and the compressor clutch is either on or off how does that work for such a switch?

I hot wired my a/c clutch last night and instant magentic coupling. I then ran the engine and alas... no cold Having just acquired the LJ78 I will assume that the a/c hasn't been used in a long time and thus requires a recharge.

2. Should I just buy one of those recharge kits from Princess Auto/Habor Freight and give it a go? Or is there a method without a vacuum pump to test for a leak?

3. Am I'm good to bypass the rheostat switch with a spst switch? there's other 'things' at play to later dissengage to disengage the clutch? (assuming all things are working)

4. What is supposed to be in the space on the right side of heater/aircon control panel? Seems a good place for a switch, any cool switches someone can recommend?

 

[GTSSportCoupe]

1. If to turn on the a/c is done via a rheostat switch and the compressor clutch is either on or off how does that work for such a switch?

I hot wired my a/c clutch last night and instant magentic coupling. I then ran the engine and alas... no cold Having just acquired the LJ78 I will assume that the a/c hasn't been used in a long time and thus requires a recharge.

2. Should I just buy one of those recharge kits from Princess Auto/Habor Freight and give it a go? Or is there a method without a vacuum pump to test for a leak?

3. Am I'm good to bypass the rheostat switch with a spst switch? there's other 'things' at play to later dissengage to disengage the clutch? (assuming all things are working)

4. What is supposed to be in the space on the right side of heater/aircon control panel? Seems a good place for a switch, any cool switches someone can recommend?

I would not recommend messing around modifying the system until you actually know what the problem is. Most likely the pressure is low. The A/C control switch/rheostat connects to an A/C control circuit I believe (A/C Amplifier?)

Best option is to bring it to an Automotive A/C shop and let them fix it for you. Next option is to try charging it yourself and see what happens.

My Red-Tek kit lasted ok with a fill up every couple years. However this year I'm taking it to the next level. I have a brand new compressor, drier and set of seals I'm going to install. Normally after this type of work a shop would purge with nitrogen, look for leaks, evacuate it, and add the refrigerant. Apparently with the Red Tek kit you don't have to evacuate it, so I think that's what I'm going to try.

If you search on the web, there is tons of info on DIY A/C stuff. I'd say do some searching and reading to learn about it.

 

[Domisean]

SportCoupe, did the Red-Tek kit come with the right valve to fit your low side valve? I'm in the U.S., I wonder if the requirement to switch to R134 valves will mean my U.S. Red-Tek kit will come with different valves than your Canadian kit...

 

[jblueridge]

Drive down to Charlottesville and let Hensley's Radiator shop fill your system with actual freon.

 

[GTSSportCoupe]

SportCoupe, did the Red-Tek kit come with the right valve to fit your low side valve? I'm in the U.S., I wonder if the requirement to switch to R134 valves will mean my U.S. Red-Tek kit will come with different valves than your Canadian kit...

Yes, it did come with the right valve adapter parts.

 

[Domisean]

Drive down to Charlottesville and let Hensley's Radiator shop fill your system with actual freon.

Good heads up, planning a trip to Charlottesville sometime in June, but wasn't planning on taking the truck... decisions decisions

 

[jblueridge]

Domisean,
Call and ask for Fred.
Hensley's Radiator Service

 

[GTSSportCoupe]

I have a brand new compressor, drier and set of seals I'm going to install. Normally after this type of work a shop would purge with nitrogen, look for leaks, evacuate it, and add the refrigerant. Apparently with the Red Tek kit you don't have to evacuate it, so I think that's what I'm going to try.

Finally had time to install the compressor, drier and seals. Was a pretty easy job. I only replaced the seals that were obviously leaking. Compressor came with oil in it, but I still added a little bit more Red-tek oil also. Then 1.5 cans of Red-tek 12a referigerant. A/C works awesome again! Vent temps were 7 Celsius. Not as good as the old R12 systems I know, but still plenty good enough. Nice to have A/C again! Works better at idle now with the new compressor. Before it would warm up every time I slowed down.

 

[fiery1]

So I've had some more time to diagnose the a/c system. Determined that there was a residual pressure in the system and then charged it up with 12a. If I hardwire the clutch on the compressor and run the engine, I get cold air almost immediately dropping to about 12 celsius and I'm not seeing leaks. I could possible add a bit more refrigerant but was wanting to diagnose everything first since it appears to be 'working'. The rheostat for turning on the a/c actually controls the idle speed, revving higher when turned on and low when turned off. In addition I can hear an audible click from a relay? in the dash when it's turned off and on. The wire going to the clutch is a red/black wire and goes off into a wiring bundle off somewhere... is there somewhere else off hand that I can check to determine why the clutch won't engage as intended?
Sounds like there's a low pressure switch and temp sensors that may have failed? Is there a common one that fails that I can look for/test and where is it located?

 

[jblueridge]

Yes, there is an "idle up" gizmo in the engine compartment that increases idle speed when a/c is called for.
I can't recall where the low pressure switch is. Somewhere behind the dash I think.
Temp sensor should be inside the plastic box that holds the evaporator. On my BJ74 it is on the left side against the firewall.
I think I had to disconnect some lines that run through the firewall to get that box out.

Maybe just make your own relay circuit direct to the compressor clutch.