Keeping A/C on an S14 RB25

[300Plus]

^^^ lol correct sorry was on my way out and in a hurry R12 is old and I dont think they sell it anymore

[Bwana]

I know for a fact that the sohc compressor bolts directly onto a s2 rb25. How it fits the other specific engines I can't verify but I would guess similar results with the other engines.

[mikalkouki]

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.

I know you posted this a year ago.... but I just swapped a s2 rb25 in my s14 and the rb a/c compressor wire is sevored and I'm having a hard time finding out which one it is from the ecu and or lower harness.... anyone know a color or pin location? there are like 4 or 5 different a/c wires on the ecu pinout.

[mikalkouki]

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".

sorry.... just saw this... so i guess that makes it pin 46 and pink..... thanks

[Darius]

Glad that helped. I still don't have lines fabbed up yet. I know a guy that will do it for me for $60, but I haven't gotten around to it. House projects are getting in the way right now. I'm hoping to have the lines installed by winter. This sucks that it keeps getting pushed back but oh well. The weather has been perfect this summer with only one week above 90.

[flatrate]

So for those who got there AC working, does it cycle like it should? mine isnt comes on idles up etc, but never shuts off, im getting about 32 degrees F out of the center vents... just not sure why its not cylcing like it should... what controls the cylce on these particular cars, the ambient temp sensor or the triple pressure switch??

This is a 98 S14 too BTW

[marshallpre1]

Subscribed.

[Darius]

flatrate - Yes the system should cycle. Mine does.

The triple pressure switch controls the temperature by effectively limiting how high the pressure can get in the system. The TPS should open its circuit when the pressure reaches a certain level, which cuts power to the compressor.

[flatrate]

werid, what wires did you switch around when you did the swap theres a few i switched around on the M63 connector... isnt the compressor cycled using the thermo amp in the evaporator like most other nissans of this era are?

cause it should cylce ive gotton down to 20 degrees at the center vent!! haha freaking cold but not working correctly

the TPS i thought was only for compressor protection... i keep reading about thermo amps on nissans but i dont see any in the diagrams, however the explanation of how the system works in the FSM states that the thermo control amp is what cycles the compressor based on evaportor temp, but i have yet to find a connector or anything around the evaporator

Id be interested to see what you changed on the M63 connector if anything at all... somethings missing and im unsure what it is...

[Darius]

hmm I didn't change anything on the M63 plug other than splicing into the Y/B wire from the climate control units to connect with the pink and B/P wire from the TPS. Going by memory here. There should be a diagram posted in the "RB---->A/C" thread. Since I didn't change anything in the dash, I am not familiar with the thermo switch you are talking about. I'd have to look into it.

[flatrate]

hmm I didn't change anything on the M63 plug other than splicing into the Y/B wire from the climate control units to connect with the pink and B/P wire from the TPS. Going by memory here. There should be a diagram posted in the "RB---->A/C" thread. Since I didn't change anything in the dash, I am not familiar with the thermo switch you are talking about. I'd have to look into it.

what about the purple wire on the RB harness thats normally in pin 48...

[Darius]

Refer to this thread on page 5:

rb-a-c-t210269-160.html

[flatrate]

Well i think i have determined the problem, i can get it to cycle if i overcharge it a little bit, however thats not how its intended to work...

The stock AC compressor on the KA is a V6 varible displacement compressor meaning it can change temp by actively changing the displacement of the ac compressor thus preventing evaporator freeze up.. it works well more stable temps the compressor clutch last longer cause theres no constant on-off's however

The RB ac compressor at least the earlier ones are not variable thus work like most older cars do, ( uses a temp sensor in the evap coil to open and close the circuit to the ac compressor clutch relay, which in turn regulates the tempature from the evap coil (very simular temps as your vent)...

The triple pressure switch IS a failsafe for over/under pressure its not there to cycle the AC compressor, to many things can effect high side pressure (which is where the switch is) ambient temp, humidity, oil levels etc..

So if your cycling off that switch its because your running to much head pressure and its shutting the compressor off... which probably wont hurt anything but its surely not intended to be used this way...

Im going to be installing an adjustible temp probe/switch into the evaporator and route it in series with the B/P wire and i should be set..

you could also use a probe from pretty much any vehicle to wire in, but an adjustible one would be neat so you could custom tailor your AC temps...

Discuss

[jamanrr]

So 300 Plus is this the same on an sr as what you did? the wires look the same and if I read it correctly the pin 46 is a power ground which the ecu reads as the a/c compressor is engages. So, basically to get the ecu to see the a/c as being ON you took 2 ground wires from the F4 car plug side and ran it to the pink 46 ecu pin so that when you press the switch it shows the compressor as on? is this correct and I wonder if this would work the same on my Apexi Power FC series 3 commander. It currently does not read the a/c compressor as being engaged so it does not raise the idle up like it should. I also have the heat shielding like you do but it would be neat to control the idle up like it should. I will also be recirculating my BOV so hoping this will help with the idle stability as well. thanks

[S14_koukilover]

i kno this is an old thread 300plus but can i get a diagram swapping my series 1 my 97 240sx and would really love
to keep my a/c great rite up on it was searching for days on how to get my a/c working