Some Air Conditioning Fix Thoughts....

[Ramius83]

Ok, I am determined to get the A/C system to work properly once the RB26 is installed.

We all know that the only real main problem is the wiring. How are we gonna get the system to be monitored with the pressure switches to activate and deactivate the compressor as needed. On the KA, the ECU does most of the monitoring with the aid of a triple pressure switch. And that I have researched, the RB's A/C Controller does most of the monitoring with a dual pressure switch, and that I have been told. And with comparing the wiring schematics from each car, they are CLEARLY different.

And we all know that when the lines are hooked up and charged, all that is needed to run A/C is to give the one wire going to the compressor power. But as many have seen, we really don't know how long to keep the compressor running before it needs to be deactivated to avoid blowing the A/C system.

Well, I "think" I have come up with a fast and easy fix for this.

The A/C compressor runs for a certain amount of time when the A/C is on, then it is shut off when it reaches its maximum pressure that the triple pressure switch sees. Now, while the KA is still in the car and the A/C works, I am gonna monitor the time intervals of when the A/C compressor is turned on and when it is turned off. So, let's say that when the A/C is on, the compressor runs for 1 minute and then is off for 30 seconds, but is then turned back on for about a minute again, as so on and so on. Well, what I have been thinking is installing a timed relay, or a set of timed relays. Run a power wire from the A/C module to the compressor that is activated whenever the A/C button is pressed. Then, interrupt that wire with a timed relay. So it sees the 1 minute on and then the 30 seconds off.

Does this sound feasible to anyone else before I tackle this?

[Joe]

that wont work because if you are working the system hard in the dead of summer the compressor will be on for a longer period of time, or if you have it on a lower blower motor setting it will need to be on for a smaller period of time. you need a way to have the computer control it, why not just have lines made with the double pressure switch in it and run wires to the skyline ECU?

[Ramius83]

However though, the compressor only compresses the air in the lines at one single rate. It is the actual blower motor that moves that cold air from the lines to the vents. So, even if the rate at which the lines are discharged are different from low to high speeds, it may only be a few seconds difference, even between now and summer time.

[Joe]

However though, the compressor only compresses the air in the lines at one single rate. It is the actual blower motor that moves that cold air from the lines to the vents. So, even if the rate at which the lines are discharged are different from low to high speeds, it may only be a few seconds difference, even between now and summer time.

the rate differs more than a couple seconds, honestly you are going to make more problems than its worth. just run the skyline AC lines with the double switch and run the wires. no second guessing, no worrying about blowing your compressor apart. any compotent AC shop can make you any kind of custom line you need with any fitting, switch, etc.

[JonPowell]

The time it takes the system to freeze up & overwork the compressor is relative to the ambient temperature & humidity.

The compressor moves the freon through the system, yes...and it does so at a certain rate, yes....but that rate TOO is relative to the temperature of the freon & the varying viscosity caused by temperature change.

This isnt a black & white area where TIME is the factor in determining proper operation. This is a subject where PRESSURE dictates proper operation times & shutdown times. You are over simplifying a situation where, for lengevity of the compressor, you NEED to monitor pressures inside the system & control the compressor based on those.

I dont know exact numbers so dont quote me on this, but take this example in consideration.

Ambient temp(outside the car) is say...90º...nice warm day where you would want the AC. It would take say 15 mins for the system to freeze up & maybe another 1 for it to cool thaw...

Now say its a warm 75º day with HIGH humidity...you AGAIN want AC....this time it takes say 9 mins for the system to freeze and maybe 5 seconds to thaw because the starting point of your freon was much lower.

If you run that system for another 6 mins based on your 90º research.....POP!

Good idea thinking about the situation, but this solution WILL NOT WORK unless you exactly duplicate the situation every time you run the AC.

[Bluefire]

It seems the best way would be to make a custom bracket for the ka compressor. Its gonna be a pain in the butt to get it aligned correctly but once you do, you could probably make a few extra brackets and make some extra money on it

-Bluefire

[Wulfgang]

You guys are all pretty much wrong except for Jon.

There is no "computer" controlling the A/C cycle. Not true, and I wish people would quit saying that. How often does this show up??? Maybe once every three months or so. More often in summer, of course. And the same wrong information keeps coming up.

A/C control is simple in our cars. We have a temperature switch. THAT IS ALL!!! No computer, nothing like that. Just a temperature switch (aka thermo control amplifier). The sole purpose of the temperature switch is to keep the evaporator core from icing up, which it will obviously do if the air coming in is cooled below the freezing point (32ºF).

It works like this: you turn the A/C switch on. The compressor kicks in and the air gets cool. Depending on load, the air may get too cold (like somewhere around 34ºF, with enough room for safety above 32ºF). So if that happens, then the thermo control amp turns off the compressor and waits until the air temperature climbs back up to say 36ºF. Then it kicks the compressor back on. Simple.

That's the basic operation. Everything else is just there for safety. For example, the pressure switches guard against refrigerant leaks or overcharging, which could destroy the compressor. The ECU control is there to shut off the A/C when you put the pedal to the metal or if the engine overheats. Any of these things will open the A/C clutch relay circuit and shut off the compressor, taking the thermo control amp out of the loop. After the problem is fixed (engine cools down, you lift your foot off of the gas pedal, recharge the system, whatever) the A/C clutch circuit is again closed and control is returned to the thermo control amp.

But in a properly charged and working A/C system, the compressor cycling is COMPLETELY controlled by the thermo control switch.

[Ramius83]

Ok Jon and Wulfgang, thanks for your help on this.

I didn't take into consideration the varying ambient temps, but that does make sense. That would be the only thing to really turn down my theory, so it doesn't make me feel to bad lol.

But, with looking at both wiring diagrams for the S14 95 240 and the R32 RB26, I still can't get it right on how I need to adapt everything. Anyone have an idea on what exact pinouts on the RB ECU match up to the stock KA A/C system?
Modified by Ramius83 at 8:34 PM 12/9/2004

[Wulfgang]

..... Anyone have an idea on what exact pinouts on the RB ECU match up to the stock KA A/C system?

Modified by Ramius83 at 8:34 PM 12/9/2004

Yep. Take a look at my RB20 into S14 wiring guide. The R32 RB26 is essentially the same beast once you strip away the automatic temperature control unit and all of the extra temperature sensors.

[Joe]

You guys are all pretty much wrong except for Jon.

There is no "computer" controlling the A/C cycle. Not true, and I wish people would quit saying that. How often does this show up??? Maybe once every three months or so. More often in summer, of course. And the same wrong information keeps coming up.

A/C control is simple in our cars. We have a temperature switch. THAT IS ALL!!! No computer, nothing like that. Just a temperature switch (aka thermo control amplifier). The sole purpose of the temperature switch is to keep the evaporator core from icing up, which it will obviously do if the air coming in is cooled below the freezing point (32ºF).

It works like this: you turn the A/C switch on. The compressor kicks in and the air gets cool. Depending on load, the air may get too cold (like somewhere around 34ºF, with enough room for safety above 32ºF). So if that happens, then the thermo control amp turns off the compressor and waits until the air temperature climbs back up to say 36ºF. Then it kicks the compressor back on. Simple.

That's the basic operation. Everything else is just there for safety. For example, the pressure switches guard against refrigerant leaks or overcharging, which could destroy the compressor. The ECU control is there to shut off the A/C when you put the pedal to the metal or if the engine overheats. Any of these things will open the A/C clutch relay circuit and shut off the compressor, taking the thermo control amp out of the loop. After the problem is fixed (engine cools down, you lift your foot off of the gas pedal, recharge the system, whatever) the A/C clutch circuit is again closed and control is returned to the thermo control amp.

But in a properly charged and working A/C system, the compressor cycling is COMPLETELY controlled by the thermo control switch.

hmm...i stand corrected. i thought the ECU was more intergrated with controlling the cycling...

[Ramius83]

Thanks so much.

According to the R32 GTR Manual I have, the RB20, RB25, and RB26 share the almost identical A/C system wiring schematics.

If your guide isn't clear enough for my "dead brain", would you mind if I bothered you for your help via email or private message? Thanks again.

[Ramius83]

Ok guys. I drew up a diagram about how Wulfgang's write-up says to do. Let me know if it is ok or not.