185 A/C issues on 205 swap

[martyRC]

Is there any update on the a/c? Is it working by now? I'm planing to do the same swap!

[phattyduck]

Not sure it will help exactly on this thread, but I was able to get my AC 100% working on my ST205 motor in an '89 Camry. The Camry AC amp controls everything but idle-up. The original signal to the Camry ECU was straight from the power to the AC clutch (12V = AC on). The ST205 activates the idle-up when one of the signals is grounded (don't have my notes with me, otherwise I'd know if it was AC or ACT or whatever). All I had to do is connect the signal to the AC Magnet Clutch Relay to the correct wire from the ECU.

This leaves the high-RPM cutoff in place and allows the AC amp to cycle the compressor when evaporator temps get too low.

-Charlie

[belanger33]

I have a question after reading the whole thread...

-My A/C does not work in the GT4 RC 1991
-Lately, i have converted the EFI system with an ST205 gen 3 ECU
-I want to get my A/C to work again, so will i have any issues because of the ECU switch???

Thanks(sorry if its not the intended subject of the thread)

[CMS-GT4]

Is there any update on the a/c? Is it working by now? I'm planing to do the same swap!

Not yet. I think there might be something wrong with my compressor.

I have a question after reading the whole thread...

-My A/C does not work in the GT4 RC 1991
-Lately, i have converted the EFI system with an ST205 gen 3 ECU
-I want to get my A/C to work again, so will i have any issues because of the ECU switch???

Thanks(sorry if its not the intended subject of the thread)

If you are running off the 205 ecu you can uplug the act wire from the ecu and the compressor should turn on. I am not sure if this causes any other problems though.

Not sure it will help exactly on this thread, but I was able to get my AC 100% working on my ST205 motor in an '89 Camry. The Camry AC amp controls everything but idle-up. The original signal to the Camry ECU was straight from the power to the AC clutch (12V = AC on). The ST205 activates the idle-up when one of the signals is grounded (don't have my notes with me, otherwise I'd know if it was AC or ACT or whatever). All I had to do is connect the signal to the AC Magnet Clutch Relay to the correct wire from the ECU.

This leaves the high-RPM cutoff in place and allows the AC amp to cycle the compressor when evaporator temps get too low.

-Charlie

If you could check your notes, this might help us out a bit. I know if you remove the act wire the ac should turn on, so maybe grounding it could be the solution.

[CMS-GT4]

So I am back on this. This is my priority project. I did get the AC running again. Just pulling the ACT wire does allow the AC to operate. Mine was not because the pressure was not in the correct tolerance. I am currently swapping in a lower millage compressor since I have to get mine refilled. To test I pulled the pressure sensor plug and jumped it to by pass the sensor.

I read around online that when the AC is activated the map from the ECU changes, per the MR2 rev3 swappers. I do not know how true this is, but I am trying to learn to properly use my multimeter so I can figure out what kind of signal the ACT wire sends. I will then either try and simulate that signal to the ECU or I will put a switch on it so that I can connect/ disconnect on the fly when AC is not in use.

[RedCelicaTRD]

The ecu does not need different maps. It simply hits different load points on the same map due to the increased load from the compressor. Also, you won't be able to tell what type of signal by using a multimeter. Unfortunately you need an oscilloscope.

[CMS-GT4]

So at this point, I guess I should just dump a switch on it and call it a day? That'll save me a lot of time in anyhow.

[RedCelicaTRD]

After looking at some of the wiring diagrams I don't think ACT has a signal "type," it is just going to be a voltage or zero. I'll look over both systems more in depth tomorrow and see if I notice anything.

[RedCelicaTRD]

Josh, do you have the ST205 ECU controlling the A/C idle VSV or is it still under control of the ST185 A/C amplifier? Is it still in series with the A/C pressure switch?

Also, do you have the A/C clutch relay being controlled by the ST185 A/C amp still?

[CMS-GT4]

AFAIK the amp is still in control of all of the AC system. Other than pulling the ACT wire, I made no changes to the oem AC wiring.
BTW, I was looking at the AC section in the BGB and it shows the pins of the amp as well as what should be detected on the wire. The problem is, I am unsure what pin it is. Not sure if that section helps.

[RedCelicaTRD]

What engine harness are you using?

[RedCelicaTRD]

Nevermind, I found you are using a repinned 185 harness.

[CMS-GT4]

Did you ever have any luck figuring out what they wire was for?

[RedCelicaTRD]

Sorry, I got caught up with school/work. From what I found some of the wires were renamed, but the purpose was essentially the same. However, I think the signals are inverted after they renamed (what was 5V is now 0V). You said you have the st205 diagnostic sheet that has the voltage levels for the signal wires during operation, correct?

On a side note, it looked like early 90's Toyota Pickup guys had a similar problem when swapping in a 5vzfe. If I remember right they used some simple circuity to fix the problem. If we can verify all we need to do is invert the signals, it should only be about $15 to fix the problem.

[CMS-GT4]

No prob, thanks for looking into it. I know my solution will work, but I rather resolve it 100% than a band aid fix.
I just have the 205 bgb, but I can see if I can hunt down a more detailed page.