185 A/C issues on 205 swap

CMS-GT4

Active member
So I am trying to sort out my AC on the st185 and the problem is, I know very little about ACs. I have upgrade lines for R134.

I had to 205 compressor on the car, but I took it off because I figured it was not compatible.

The magnetic clutch will not engage on the compressor.

Everything in the AC system is 185 except the AC idle up valve.


• I was looking at the ECU wiring and the 205 ecu controls the AC idle up valve, and the 185 does not.
So what controls the 185 AC idle valve?

• The 185 ECU has a control for the magnet clutch, but the 205 ecu does not. In its place is a second A/C amplifier.

I have included the AC portion of the ECU guide.

This copy is of the 205 bgb, in red is the 185 components.

Any insight is appreciated.

picture1yw5.jpg
 

CMS-GT4

Active member
MR2 Guru helped me find some information.

The MR2 guys run into the same problem when trying to swap to a REV 3 3sgte.

Here is the link.

http://www.mr2oc.com/showthread.php?t=2 ... n+3+AC+fix

The Air Conditioning (AC A/C):

The symptoms: The AC light turns on on the dash, but doesn't do anything -- the AC magnetic clutch isn't engaging.

The solutions: Aparently the Gen3 runs the AC in a similar manner to the NA as it uses a pink/green wire in IE3 to trigger the AC amplifier as to when it's supposed to turn on the AC compressor. We found this wire present, and the car seemed to be wired on the kick panel for this wire also, but the gen2 harness we removed didn't have this wire. So we cut this wire. We also found that there was supposed to be a tach signal from the ignitor going to the AC amplifier on IE4 pin 10. This was also an empty pin on the wiring harness for the Gen 3 -- so we inserted another pin, and wired it to splice in to the IE1 connector's tach signal to the dash.

The other wires missing on the gen 3 harness appear to be the idle up wiring for the idle up VSV -- but I believe as long as the gen3 ecu is getting the signal that the AC is on (black/white wire) it is controlling the idle up VSV as that appeared to be what was happening.

I hope this helps some people out there with 3rd Gen swaps.


So, they look to the solution that the NA car uses to activate the magnetic clutch on the compressor.
I looked at their info, but started thinking I wonder if the 5sfe on the st18x works the same way. I checked out the ecu pinout for the NA celica and its much like the 205 as far as the AC goes.

Here are the pinout pages from the BGB.
st185: http://img242.imageshack.us/img242/4591 ... b17ph8.jpg

St205: http://www.celicatech.com/imagearchive/ ... EG-122.jpg

5sfe: http://img178.imageshack.us/img178/5624 ... b17fz6.jpg

So I think if I can determine how the 52 celicas activate their magnetic clutch, I can modify my wiring and have a working AC system.

Anyone hav any input?
 

Rpz123isme

New member
This is kind of funny and sad! I had a lot of befor and after wiring pictures from when I did my a/c conversion! I have a gen 2 motor, na pump and a gen 2 computer with a n/a dash setup. It was a pain in the ass..... but the white with a black stripe wire is the one that activated the valve and controlled the main part of the ac. If you use the black with a white stripe wire you will have huge ass problems because you are just engaging the clutch which will work but not for long! btw after using the white/blk wire My ac did not engage until I had at leats some r134 and the motor going!
 

CMS-GT4

Active member
I have both the 185 and 18x AC wiring diagrams in front of me. I am just trying to make sense of them and relate them to the MR2 fix.
 

CMS-GT4

Active member
Can you remember how the NA activates the Magnetic clutch? My entire system is setup to work less the signal to the compressor.
 

CMS-GT4

Active member
We found that if you remove the ACT wire on the bottom of the ecu, the compressor will work. However, the car runs poorly. It idles lower and does not pull as hard at speed. Almost like a vac leak or timing being pulled. So I have charged the AC, but I had to replace the ACT wire in the ecu so the car drives normally.

Anyone have an understanding of what information the ACT pin is looking for on the ecu? Maybe I can replicate it like I did with code 54 and then leave the wire unplugged for the ecu.

Or maybe what info the amplifier needs to activate the clutch.
 

gtfour-wrc

New member
CMS-GT4,

Did you ever figure out how ACT works on the Rev2 ecu?

I'm having issues getting a Rev2 AP Engineering Power FC running on my 1990 gt4 after re-pinning to jdm 91-93 harness. The car runs fine but the AC1 and ACT pins seem to short out. Both pins have no power when A/C is off. Turn the A/C on and only the AC1 pin powers up. If I probe the ACT pin with a grounded probe, the engine idles up.

Do you know if the 93-95 USDM Alltrac A/C pin is powered when off?
 

CMS-GT4

Active member
I never sorted out the issue. MY car has been away at a body shop for some time, so I have not been able to get to it. I had planned on reviving this thread as soon as I get my car back as A/C is a priority for me.
 

urbandork

New member
CMS-GT4":27atmjlm said:
So I am trying to sort out my AC on the st185 and the problem is, I know very little about ACs. I have upgrade lines for R134.

I had to 205 compressor on the car, but I took it off because I figured it was not compatible.

The magnetic clutch will not engage on the compressor.

Everything in the AC system is 185 except the AC idle up valve.


• I was looking at the ECU wiring and the 205 ecu controls the AC idle up valve, and the 185 does not.
So what controls the 185 AC idle valve?

• The 185 ECU has a control for the magnet clutch, but the 205 ecu does not. In its place is a second A/C amplifier.

I have included the AC portion of the ECU guide.

This copy is of the 205 bgb, in red is the 185 components.

Any insight is appreciated.

picture1yw5.jpg

hook what ever wire off the 185 ecu that creates a closed system to the PIN on the relay which is tied to the PIN receiving power to the coil (of the relay).

Doing this will make the naturally open relay close, sending power to the magnetic clutch

D/L ing the 185 EWD now and ill get back to you... ive swapped a rev 3 into my 6th gen and planing another one into my 165.... for the 6th gen however i only had to switch a few wires from different pin locations on the plugs.
 

urbandork

New member
If ur using the 185 a/c amplifier with a 205 relay then the the L-Y (blue-yellow) wire of pin 1 plug IJ1, which leads to the pin 3 on the 185 EA1 plug is the one that completes the circuit and magnifies the relay. This allows the relay to send power to the magnetic clutch.

If you have the 205 relay in Junction Box 5 then the L-Y wire from ur 165 amplifier should go to the 205's a/c mag clutch relay on leg 2 of that relay or pin 2 plug 1D3 LHD/ pin 10 plug ID2 RHD

This should get the 205 relay to work and send power the 165 a/c mag clutch
 

urbandork

New member
as for the inputs to the ecu im assuming ur using a 205 ecu which has to lines coming in from the ac amplifier which are ACT on B pin 21 and an ATC on B pin 8. Theres also a line going out from the ecu on B pin ac1 which sends info to the 205 ac amplifier which im guessing ur not running. (right)

If you are using the 185 amplifier then one of the wires from the amplifier and one off the relay (plug IG1 pin 4 off the relay and IJ1 pin 3 from the amplifier) should be going back to the 205 ecu ACT and ATS pins on the ecu....as far as the out going wire on the 205 ecu (AC1 B pin 10) if ur interfacing with the 185 amplifier it shouldnt be needed..... I THINK :doh:

hope this helps and doesnt make things more confusing
 

celi_wabbit

New member
The simplest way to do it is when swapping with ST205 motor, is to use your ST185 a/c compressor. No rewiring have to be done if you swap from your stock 2nd gen to ST205 3rd gen if you just use your old 2nd gen a/c.
 

CMS-GT4

Active member
I am using a 185 A/C system. The 205 ECU prevents the clutch from activating though with the ACT wire plugged in.
 

CMS-GT4

Active member
I did try it at first, but it got ruined since I did not seal it correctly when switching to the 185 head for the compressor.
 
Top