Keeping A/C on an S14 RB25

[Darius]

Makes perfect sense, but on the 1997 it is a little different because the A/C compressor relay is upstream of the triple pressure switch. So what I am proposing to do is jumper the wiring on the F4 plug together to bypass the ECU.

300Plus - I know you have been busy with your AC, but when you get a chance, could you look over the diagram I e-mailed you and give me some feedback? I'm pretty sure it will work the same and I won't have to externally add a FICD wire if it will work by grounding the ECU wire from pin 46 with the Y/B wire.

[pito2003ac]

yea should be a sticky! good info!

[300Plus]

Makes perfect sense, but on the 1997 it is a little different because the A/C compressor relay is upstream of the triple pressure switch. So what I am proposing to do is jumper the wiring on the F4 plug together to bypass the ECU.

300Plus - I know you have been busy with your AC, but when you get a chance, could you look over the diagram I e-mailed you and give me some feedback? I'm pretty sure it will work the same and I won't have to externally add a FICD wire if it will work by grounding the ECU wire from pin 46 with the Y/B wire.

Darius, resend you diagram for me, don't think I got it. But what do you mean by upstream?

On the 95 the Black/pink wire at the M63/f4 junction goes from there to the triple pressure switch then to the coil side of the AC relay. so M63->Triple pressure switch -> Coil side of relay.

I'll have my pics up today guys ! Thanks for the appreciation!

[Darius]

okay I'll resend the diagram this morning.

What I mean by upstream is this:

PUSH control unit>>AC relay (coil side)>>triple pressure switch>>ambient temp switch>>chassis ground

[300Plus]

ok here are some request pic plus a few.

here is a pic of my permacools mounted to the condenser. If you look they are offset to one side (the passenger side). this has to be done so they don't scrub on the rad support. I had to bend down a tiny tab that sticks up off the lower part of the rad support as well. no biggie just wanna stress to make sure your fans don't scrub on any wires or metal as you zip tie them into the condenser.



Here are two pics show the difference of the compressor power wires. Again you need to swap the RB compressor wire onto the KA harness already on the car.

KA on LEFT , RB on RIGHT



And here is where I mounted the drier since I'm using the greddy manifold it has to be pushed lower then its stock location. but I am using the stock unmodified lines on this side of the engine bay. they just needed to be bent a little by hand. a warning to be careful that 1. you don't kink the line and 2. that you make sure the line leaving the drier heading to the firewall does not interfere with the Throttle body linkage.

It looks close to the alternator in the pic but it isn't. It is completely against the frame rail. Also the wires to the triple pressure switch will reach in this location, but I had the plug from the skylines triple pressure switch (witch is the same with different color wires) so I used it to extend the wires a little and to give me some extra length to wire my fans through the switch(details below)



OK here is some more wiring info...

This is a pic of the triple pressure switch plug that is on the car, should be folded up near the passenger side edge of the radiator with the plug that original went to the AC fan. I cut mine off to extend the wires for safety)

Here is a pic of the plug and below are what the wires go to. If you don't extend the wires but want to wire your fans through the switch so they come on as the stock ac system would the you will still need to cut out two of the wires going to the triple pressure switch.



1) Black/pink - From the F4 plug (switched ground when AC button is pressed)2) Black - constant ground (cut it out of the harness and add a wire to a chassis ground.3) Orange/Black - Switched ground ( cut out of harness you want to wire to your fan relay coil side groun,as it will switch and connect to the constant ground to trigger the fans when the pressure is right)4) Green/yellow -this wire continues to the AC relay to apply the ground when the AC button is pressed and the pressure in the system is correct (if wired correctly as explain in my previous post)

I will try to make up a little diagram of all this, to help clarify ,when ever I get a chance. But until I believe all the info to make the system work prefectly is here. I try to explain clearly and in details everyone can understand, but let me know if clarification is needed on anything.

oh yea here is a vid or two of me pushing the AC button you can see in the vid that the idle drops about 100 rpms when the compressor is on but the motor does not struggle at all. I also had my idle set very low at when I recorded this, still had no stalling issues And I have my laptop connected to the consult port running the Nissan consult software, you can see the computer registers the AC relay as on






Modified by 300Plus at 12:38 PM 8/20/2007

[lazyboi444]

Well done... Im still kinda foggy on the idea, shouldn't the car idle up to adjust to the compressor coming on?....But good job.

[300Plus]

I believe it does "idle up" but still drops the idle a hundred RPMs as in... the compressor may pull the motor down 300 rpms and the FICD controlled by the computer compensates by adding 200 rpms, still pulling the motor down 100 rpms... make since?

all I can say is the idle lowers a little but not where it causes an issue. I've driven all around town with it on and coming off load and high rpm still doesn't stumble.

[lazyboi444]

Yeah makes since...Wasn't a issue...I was just curious....If it works with out problems not exactly the right way, Why fix it you know lol. But once again thanks....I know the wiring schematic for the 25 and 20 are a bit off but not in the A/C deparment correct?

[300Plus]

300kms on the trip meter and both the power steering and AC are running perfectly. Just a confirm

[Darius]

On the triple pressure switch, is the OR/B and B side of the switch simply for controlling the ground on the fan relay? I think the diagram in the FSM that I'm using is showing the triple pressure switch wrong.

[300Plus]

Yes, if you were to charge the system and test for continuity between the orange/black wire and the black wire. you would see no continuity until the pressure was just right and then they would connect. and this is called the "middle switch" by the FSM. Still haven't had time to look at your diagram sorry Matt. But the way the KA is wired, like I said before, way over complicated. But the black wire was grounded and the orange went back to the ecu. Once the pressure was right it would ground the wire, which would tell the ecu, then the ecu would check with several sensors, and then if all was ok it would ground another ecu pin that led to the fan relay, kicking them on. and the skyline was wired just how I'm using it, it simply grounds the coil side of the fan relay kicking it on, just cut all that junk out, I already had efans and the relays setup to a temp sensor so I just added a few wires straight to the triple switch and it grounds and turns the fans on when needed

[Darius]

Ok sweet. That makes it a lot easier than trying to mess with the existing wiring. All I have to do then is connect the B/P to the P and then both of those to the Y/B to ground the TPS when the AC switch is pressed. Then ground the B to the chassis and run the OR/B to the ground side of the e-fan relay coil. Cake.

[300Plus]

Here is a shot of the lines that were modded, by adding the RB compressor ends onto the KA lines. threw some DEI heat shielding on to protect the rubber underneath, overall they fit perfectly





Modified by 300Plus at 12:18 PM 8/20/2007
Modified by 300Plus at 12:22 PM 8/20/2007

[300Plus]

Ok sweet. That makes it a lot easier than trying to mess with the existing wiring. All I have to do then is connect the B/P to the P and then both of those to the Y/B to ground the TPS when the AC switch is pressed. Then ground the B to the chassis and run the OR/B to the ground side of the e-fan relay coil. Cake.

exactly

I know my posts are long and overly simplified, I just want to make sure I'm clear but that is all you need to do man.

[blurrbosi]

Pretty good 300!

[s14vert]

I have an s13 with an s14 motor. I'm trying to wire up my a/c and I have been reading your posting. It's so similar to mine but I couldn't figure it out to make it work with my swap. Could you please help me? Thank you!

[240z4u]

Great information, if I can ever get all the other small garbage fixed on my ride A/C is on the way!

Thanks 300, the info is appreciated.

Evan

[Bwana]

I'd like to throw in a random point...

The stock sohc a/c compressor bolts right up to a s2 a/c bracket and everything lines up perfect, bolts, pulley etc.

I don't have the stuff to try a s1 bracket or dohc compressor, but I'd guess them to be the same...

Makes it possible to find a new replacement, only requires lengthening/shortening the lines to make work. You don't even have to swap the plug.

[300Plus]

^^^^^ WOW that is and would have been great to know! I looked for awhile to get a good R33 compressor. Do you have pics of it bolted up? do the lines actually have to be modded or will the stock lines bolt up? what car did you try it in s13 s14 ?more info would help alot of ppl out

[240z4u]

Yes, more information please!

Thats great information.

Evan

[Bwana]

I'll get a pic for you later, but the lines definitely do need modified.

This is in a s13 coupe, s2 rb25.

[300Plus]

Bump for summer, mine is still working great! not a single issue

[S14-NEO]

just out of curiousty with the setup you and dairus implemented does the AC cycle normally or do you have to cycle it manually by turning off the AC switch in order to keep the evaporator from freezing...ii have not ruled out the idea of throwing AC back in my car which is one of the main reasons why i dont drive it everyday down here in hot as balls florida

[300Plus]

Yea tell me about it I'm in North Florida where we don't have the sea breeze but we get all the heat and humidity.

But yes to answer your question it cycles just as it should. the triple pressure switch is a simple setup and if the pressure in the line gets too low or too high it cuts power to the compressor. too low would burn up the compressor and two high would freeze it up. I ran it all summer last year, freezing cold and working perfectly

[Darius]

I don't have mine running yet, but it is all wired and ready to go. I need lines, a dryer, and a charge and it should cycle via the triple pressure switch like 300Plus said.

I wired my fans to turn on when the A/C is running via the DIF control unit too.

[noodl35]

I've been following this thread alot and just wanted to say thanks for the information.

One question though, would this a/c fix work for a r33 rb26dett into a 98 240sx?

[Darius]

You'll just have to look at the ECU wiring pinouts from the RB25 and RB26. It is in the back of the FSM for each.

Since I have nothing better to do right now, I looked it up for you. The RB25 and RB26 share the same pin for the A/C signal (pin 46). I don't know about wire color for the RB26, but I would guess them to be the same (Pink).

So to answer your question in one word, "yes".

[noodl35]

awesome thanks

[300Plus]

I'd like to throw in a random point...

The stock sohc a/c compressor bolts right up to a s2 a/c bracket and everything lines up perfect, bolts, pulley etc.

I don't have the stuff to try a s1 bracket or dohc compressor, but I'd guess them to be the same...

Makes

If this can be confirmed it would help Darius and everyone. If you can get a SOHC compressor and A/C lines it should just bolt right up to your S13, I don't know if the compressor has the same flange as the S14 lines but either way the lines and compressors should be easy to find here as compared to the skyline compressors and lines!

The s13 pumps will probably be R134 collant and I'm not sure if you can just run R12 (today's standard) in them... can anyone confirm that aswell?

[craz4240]

If this can be confirmed it would help Darius and everyone. If you can get a SOHC compressor and A/C lines it should just bolt right up to your S13, I don't know if the compressor has the same flange as the S14 lines but either way the lines and compressors should be easy to find here as compared to the skyline compressors and lines!

The s13 pumps will probably be R134 collant and I'm not sure if you can just run R12 (today's standard) in them... can anyone confirm that aswell?

I think you have that backwards hehehe R134 is current R12 is obsolete.