A/C wiring Q's

Silverbullet · Post by **Silverbullet** » Sun Oct 04, 2015 11:31 am

Having completely re-designed the wiring in my car now I can' t use the original MY A/C wiring since it's no longer "compatible"

Following the FSM A/C wiring diagram and after many hours of studying it and wtf moments I think I've pretty much worked out how the original system was supposed to work. Just going on what some others have said about the A/C in their cars, I take it the A/C system should only be activated when the blower fan is operating? And are both thermo fans supposed to come on with the A/C system? Also, I can confirm that the FSM says the condenser fan should turn off when you turn the headlights on!

That's what the normally closed relay usually on the strut tower is for.

Needless to say I'm ditching the headlight switching rubbish, but I'd like to know if it's a good idea to trip both thermo fans on with the A/C system, or is just the condenser fan sufficient with the main thermo still working of the temp switch in the radiator. Also in my FSM it seems the blower fan relay is triggered "on" by the ACC switch, and the A/C system can be operated whether the blower is on or not. Is it a bad idea to run the system with the blower fan not running?

steptoe · Post by **steptoe** » Sun Oct 04, 2015 12:26 pm

You understand it more than me.

If I can add some 80's thoughts by Fuji ...with even a turbo Vortex they did not supply even one add on electric fan unless you also got AC ! My Vort has no AC so no electrci fan until I sorted that ! My GLTA EA with AC and yes Christ, allah or Buddha I chucked out all the AC iron mongery for spider manifold AC and normal manifold AC !! The GLTA had a clutch fan and the add on electric for the AC - can tell it was an add on at the dealer or some dimly lit little auto electricians shop feeding off the dealership .

In warm old Adelaide, i would not muck about run both rad fans to chill the condensor up front as fast as, or, add more gadgets and wires, another little box set to your desired ambient temp to choose if both fans should come on or just one like factory specified.

No AC with headlights on - all the time ?? Not so with my GLTA ...

there is also the TX valve , werent they also switching the compressor on off.

and yes, think all AC are best wired in not to switch on unless interior fan is also on - you may freeze up the forget the technical name under tha dash if no blower.

How about duct your engines intake air through the chilled air division

Silverbullet · Post by **Silverbullet** » Sun Oct 04, 2015 4:33 pm

I plan to use 2 of the biggest modern slimline fans I can cram in there, blow through or suck through not sure yet have to see how much space with the engine and rad in place. So I think with even 1 bigger modern fan the A/C would still be happy but it's also just as easy to join the main thermo fan relay to the A/C thermo fan relay. Don't want any scary temps on those 45 degree days

Upon closer inspection, the factory A/C switch (in the cab) sends power to signal all the relays, goes through high and low pressure switches, then the thermostat on the evap, and then to earth through the 4 position fan switch i.e only earthed when the switch is on. Okay so, how can I make that happen now I'm not using the 4 position switch but a variable speed control hmmm

Jonno, the cycling on and off is down to the thermostat pinned to the evap fins; just chucked mine in the freezer for 5 minutes and heard a *click* and no more continuity between the 2 contacts

I guess it wouldn't be too hard to pipe in another evaporator and have the engine draw air through it hehe

tambox · Post by **tambox** » Sun Oct 04, 2015 7:26 pm

Air conditioner systems have a basic principle as a heat ex-changer, this is controlled/limited by pressure and temp switches.

The more flow you have through the radiator/condenser the more efficient the system will be, as this is the side that does the hard work.

Provided your compressor and gas are good, it will work well.

They are usually wired up so the compressor is controlled by the dash fan switch/pressure switches/evap temp switch. The compressor in turn controls both fans, so does the radiator temp fan switch.

The headlight bit does not exist in .au (having said that, never seen it in .au

)

Suck is better in some ways as it concentrates the air flow on the important bit, the radiator. Blow is the opposite and you may end up with over heating problems.

For the fan speed controller, you just need to set it up to operate a relay (yep another one) so that as soon as the dash fan reaches a certain speed (equivalent to position 1 on the old switch) it allows the A/C to operate. Too low a dash fan speed is pointless having the A/C on. There are plenty of voltage level relay triggers around.

steptoe · Post by **steptoe** » Sun Oct 04, 2015 9:04 pm

and, no one has mentioned diodes. MY and L seem to have a few of those soft plastic blue diodes added in to the loom under dash, and my bet is they were added in to AC looms. Used a lot of them to eventually fix a fault I caused with my three wiring jobs at once

keep it up tambox - you're good

Proton mouse · Post by **Proton mouse** » Mon Oct 05, 2015 11:44 pm

Pretty well just confirming most of what has already been said....

-Definitely put twin fans on engine side of radiator
Rig them to both come on when A/C is on, and/or if engine water temp switch goes closed circuit.
Are you going to use the 4 dedicated fan relays on the side of the Liberty engine bay fuse box for this, like I did?
I can draw up a circuit diagram of mine if you want. (yes draw, none of this fan-dangled computer generated pretty stuff

)
I've never heard of the night time curfew of A/C. I am guessing that is on early generator models??

-Definitely rig it so the compressor fires up only when the fan blower is on.
When you fit standard A/C system to a Brumby etc. there is a separate relay that fits straight into a socket in the factory loom (right near the fuse box)
This now takes on all the load for the blower and A/C 'on' signal power for the strut tower relays, and is energised when key is in ACC position.
There aren't any diodes in the standard 'MY' A/C wiring, but yours being custom may be different!!
Good luck with it all.
John

YouTube · Post by **El_Freddo** » Mon Oct 12, 2015 11:01 pm

On my L I have two pulling fans on the back of the radiator and one small pusher fan to help move more air over the condenser at low speed.

The fan speed selection switch seems interesting!

Cheers

Bennie