3UZ Conversion and Air Conditioning

[JZH]

This relates to the later (6-speed) LS430 3UZ ECM.

I'm trying to work out the wiring for the A/C on my Hiace H200 conversion. I want to use the vehicle's existing a/c, which (a) works and (b) includes an additional rear system.

The Hiace compressor is different from the UZ-type (so it won't bolt on directly to the 3UZ), but it is similar in design/function to a later 1UZ, so physically the ideal solution is to buy one of those and get new hoses made for it. It has a clutch pulley and lock sensor like a VVTi a/c compressor, rather than a clutch and solenoid like the early 3UZ a/c compressor, or no clutch and a solenoid like the later 3UZ a/c compressor.

Using the Hiace's A/C Amplifier and a late 1UZ compressor, my wiring should be straightforward:
(There are several other terminals on the A/C Amplifier, but not shown.)

The Lock Sensor needs a reference speed signal in order to function, so I was planning to get that signal from the +S terminal on the LS430 Combination Meter (which repeats the speed input signal generated by the vehicle's ABS computer--or, in my case, by an All4Swap LS430 instrument panel interface box).

I think I will add a new MG CLT relay and wiring and run that through my engine harness, rather than try to re-use the OEM wiring and relay--seems cleaner.

However, I'm not sure about the function of the CAN-bus connection between the A/C Amplifier and the OEM ECM. I suppose this connection is what tells the engine to increase the engine's idle speed when the A/C compressor is engaged? According to the wiring diagram, there is also a terminal for an "Idle-Up" switch on the A/C Amplifier, but my Hiace didn't have the switch, so I don't know if that terminal/function is enabled on my A/C Amplifier. My guess it that it would likely be present, so I should be able to use the All4Swap box to provide a GND to that terminal on the A/C Amplifier. Is there another way?

Ciao,

JZH

 

[George_R]

your a/c unit and ecu are using different CAN protocol so you definitely need one of my devices

 

[JZH]

Thanks, George. I already have your LS430 instrument panel device, so in that case I can further simplify this diagram as shown below:



(Of course, the various inputs to the All4Swap device will also be connected to, e.g., the LS430/3UZ ECM via CAN-H and CAN-L.)

I don't think there would be an issue with also including an Idle-Up switch on the dashboard, but it would probably not really be necessary.

Cheers,

JZH

 

[JZH]

Hmmm. Thinking about this again, P5 on the Hiace A/C Amplifier is an input, not an output, so it would not itself provide a (-) to the All4Swap box (which effectively controls the 3UZ engine speed via its CAN connection to the 3UZ ECM). So, for the All4Swap box I need to find a way to supply a GND when the A/C is switched ON.


Although I could probably create one using a relay, the only A/C-switched GND I can see on the Hiace EWD is for the Magnetic Clutch relay, but I should be able to tap into that circuit easily. (I'm making a parallel tap using Sumitomo 6098-5585 (m), which mates with the OEM 90980-12557 (f) 40-pin A/C Amplifier connector and the appropriate Sumitomo 0.64mm terminals--but this could also be done by cutting and splicing into the wires.)

However, I think this means the dashboard Idle-up switch, connected to the A/C Amplifier, would not do anything (and connecting it to the All4Swap box would also activate the Magnetic Clutch when the Idle-up switch is ON). Fortunately, I don't absolutely need that option.

Ciao,

JZH