RA28/23 Factory Aircon Wiring

**Andrew_H** · 11-07-2006, 10:51 AM

I am wiring up the Aircon on my RA28 with an 18RGEU with factory aircon equipt.
Which wire activates the clutch on the compressor from the factory loom?
I have a loose black wire with a red stripe next to where the original compressor would have been (for the 18RC) and a loose plain black wire. They are next to the engine mount on the RH/driver side.
According to the Haynes manual wiring diagram there should be a black wire going to the -ve terminal of the ignition coil and the clutch should be activated by a black wire with a white stripe (not red).
On the passenger side there is a black wire with a yellow stripe that is free too.
The real annoyance is that they all are showing 12-13V on the multimeter whenever the car is running whether I have the A/C switch on or off.

Is the A/C switch in the cabin the same sort as the rear demister switch? I have spare demister switches that have the same plug config as the wires that go to the A/C but I am not sure if it should be a different variable switch or just straight push button on/off.

Thanks.

**TA-022** · 11-07-2006, 11:52 AM

Same plug ... demister switch should still do the job.

Sounds like you need to find a wire in the bay that is 12volt when the switch is on and nothing when off.

EDIT: [didnt see this bit in 1st post] remembering std motor is 18rc and that the compressor is on the drivers side not passenger like the 18rg. So you may find the wire is on the drivers side not passenger where you are looking.[ end edit]

Otherwise ive got a labelled ra28 loom with aircon at home sitting in the project and i can check the wiring for you.

Also try a 'continuity' test with a multimeter from the aircon switch to your strays in the engine bay. That way you'll find the wire going into the bay from the switch. And check which wire / if any on the back of the switch has 12volts when turned on ... this will also help ID the trigger wire and tell you if the switch is working ... as long as it IS getting 12volts to start with in case you havent checked yet.

Hope this helps (sorry bout the novel

)

Nathan

**o_man_ra23** · 11-07-2006, 01:14 PM

Im in agreeance with Nathan, wise words mate. Other thing to look at, is what is the colours of the wires on the back of the switch?? Ive come across many anomalies with the wiring in my RA23, as the wiring diagram is from the haynes manual, which is made mostly for the american cars, so it doesnt show T motors either.

Cheers, Owen

**Andrew_H** · 11-07-2006, 02:13 PM

If you could check your loom at home and tell me what colour the wire is that would be great.
The car is off getting gassed right now so I can't do a continuity check today.

**Mos** · 11-07-2006, 06:27 PM

Does these cars run pressure switches and thermostats?

In most (not that much) newer cars the A/C will only turn on the compressor if the blower is running, if the refrigerant levels are high enough to activate the pressure switch, and the thermostat (sometimes called A/C Amplifier) has a valid temperature and rpm signal.

Depending on how it's wired, there could be a number of variables in the equation.

Regarding wiring diagrams, I have found (non obvious eg wrong pin number) errors in factory manuals/diagrams, and even the IS200 Lexus publication has a shitload of stupid and very obvious errors that any editor with half a (wiring) clue would have picked up.

Mos.

**o_man_ra23** · 12-07-2006, 07:57 AM

Originally Posted by Mos

Regarding wiring diagrams, I have found (non obvious eg wrong pin number) errors in factory manuals/diagrams, and even the IS200 Lexus publication has a shitload of stupid and very obvious errors that any editor with half a (wiring) clue would have picked up.

Mos.

Sounds like a manager checked it, not an engineer... either that or it was checked at 2am after a straight 24hr shift trying to get the publication finished (moral: dont ever rush a publication, its better to be late than wrong)

Cheers, Owen

**TA-022** · 12-07-2006, 10:46 AM

Checked my loom and another at Celica Spares... i got Black with white trace both times.

Also possible that the wire was changed previoulsy with other wiring work.

Best bet is to find a on off wire triggered by the ac switch or the continuity test from the switch test.

And by looking at it its a single wire that provides 12v to engage. Easiest thing if you cant find the wire is to simply run a new one.

**Andrew_H** · 13-07-2006, 05:10 PM

Thanks.

Nothing is ever easy.

**Andrew_H** · 14-07-2006, 03:22 PM

For future reference the wire is black with a white stripe and is located at a T-Junction in the loom where the wires that go to the windscreen washer bottle split from the main harness.
A demister switch works the same as the A/C switch.
Lucky I got it working for the balmy 11°C today.