Tuesday, January 14, 2014 - 05:01 pm, by: Scott Vim(1uz1jz)
So only works below 27-28 degrees. I have taken it so many places. Barely turns on days like this (40 degrees- once it hits operating temp won't come on at all) On all gauges high pressure is well within range when it faults. Has plenty of gas 134a. Earth gets cut from relay, if you jump relay it will run all day long. Taken it to about 10 different people. Heard a lot of different things. Some think pressure switch but guy from ksr aircon strongly disagrees. Thinks ecu is cutting earth. Another guy also think this, he was sure its electrical mst likely ecu request pin. Swapped ecus and same problem. So getting suggested same thing. Going around in circles.The Ksr guy wants ecu pinouts which for a chaser (JZX100) Isn't exactly easy. And he wants the car for a couple of days. He wants to bypass the ecu but I don't understand I told him I bought a spare one and same issue. Should I just give up?
Tuesday, January 14, 2014 - 09:48 pm, by: Robert Day(Lexsmaz)
As has been said it could be as lot of things but if it temp related it makes me think it's the pressure switch at fault ??, I have never checked these pressure switches but i,m guessing they go open circuit when the pressure is to high .. Take the plug off the pressure switch & use a multi meter to check the 2 terminals on the switch when the motor is cold & see what the readings are I'm guessing they should read 0 ohms give or take a bit & recheck the same switch when the A/C is not working / playing up & check the same switch & I'm guessing it will read open circuit or O.L ..
Wednesday, January 15, 2014 - 01:00 am, by: Robert Day(Lexsmaz)
Jumping the clutch like you did has by-passed so many things, you need to do it step by step otherwise you might replace the switch & its still something else, your call or choice, but could get expensive changing things willy nilly ..
Wednesday, January 15, 2014 - 03:08 am, by: Boris Siljanoski(Z2tt)
If you have applied direct power to the clutch you have bypassed the entire System and you cannot assume it is the pressure switch when you did not isolate it to that.
Assuming on hotter days as naturally high side pressures are higher than colder days, this condition can be simulated by restricting airflow to the condenser, holding revs up and running the fan on maximum on fresh with hot engine and bonnet up, now testing can begin.
I take it your Chaser only has one pressure switching unit with LP MP and HP contacts
Bypassing each of these one by one is going to rule out the problem, you need to be very sure that your car will not exceed safe pressure limits when doing this.
Alternatively you can just replace the pressure switch with a suitable type if you have not eliminated this before but remember you want to try avoid doing things that are likely not to fix the issue.... that being said the pressure switch is a very obvious area to start with so long as your A/C Guys have ruled out the pressures are all normal under various conditions.
Compressor cutting out is due to something happening somewhere in the electrical circuit, can be anywhere from Climate Control Unit, to ECU, to Relay, to Pressure Switch, a way to do this can be to make test points between each component and hook up a multimeter, example if the ECU Request pin is mysteriously losing power and this is the cause, backprobe that pin and drive around, same goes for the relay trigger pin from the ECU.
If you can rule these out it will be very likely the cause of it is the pressure switch so long as you are 100% Sure pressures do not exceed the specs of the pressure switch on hotter days.
Wednesday, January 15, 2014 - 08:04 am, by: Scott Vim(1uz1jz)
One other clue is when it cuts the compressor the a/c fans come on even though the high pressure hasn't moved. So it thinks there is a situation requiring the fans.
Tuesday, October 24, 2017 - 05:09 pm, by: Scott Vim(1uz1jz)
Each summer I have a crack at this and hasn't been solved yet. I have been told by some that the pressures move and by others that they don't move. I'm tempted to buy a gauge and see for myself. Did the pressure switch and issue hasn't changed. Climate control unit was replaced in 2013 as original unit wouldn't turn the compressor on. It seems to be better when the bonnet is open so that suggests pressures are too high. I have a front mount intercooler in the way possibly adding to the issue should I wire up a/c fans to run on a switch to see if it helps issue?
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