1988 HJ75 2H AC Troubleshooting (1 Viewer)

[Ozzy75]

Hi All, long time lurker first time poster... I'll start off by saying that these forums have been an absolute huge help in the slow restoration of my HJ75 so a huge thank you!

I've decided to move onto my next project of getting the AC working in the old girl. I purchased the ute with not much history on it, AC hasn't worked since I brought it 11 months ago. I'm going to give it a decent crack trying to fix and repair most of it as I'm living extremely remote in Western Australia and our closest AC tech is 2 hours drive and 2 hours home away and most likely quite costly there is no way for me to leave my car with him either besides spending the day in town waiting for a re-gas.

Now I've checked over most of the main component's and I'm assuming this was a AC factory delivered HJ75 guessing from how well every thing looks to be in place.

I've got a few questions and issues which I'll list below to hopefully make it easier for others to read and track.

#1 My AC compressor has had its power wire cut or broken at some stage, I've tested the clutch by running a hot wire direct from the battery with the ute running and it engaged and ran quite smoothly which I only did for about 5 seconds, I'm unable to find the original wire that runs to the cab that delivers power though as all the plugs in the area I tested are not showing any power on them with the AC and fans turn on in the cabin so I'm unsure exactly which one it could be. This then lead me on to chasing the below problems..

#2 I decided to check to see if I could hear the AC amplifier making any noises when the AC is toggled to the up on position. The box is indeed giving one solid click when turned on and one solid click off when turned off sounds like a relay should. Board to me looks ok? nothing obviously blown or burnt out?

#3 I tried testing all the wires off the rear of the AC amplifier with a test light and only see power on the blue wire which becomes active with the car on ACC or RUN there doesn't seem to be any power coming of any of the other wires... Now below is what I can figure out so far...

7 Cable plug that goes into the AC AMP
Solid blue - power from the ACC I believe this also runs down to my low pressure switch on the left side of the AC box below the passenger side
Black/yellow - runs from the low pressure switch (unsure should this see power if the pressure switch see's enough pressure in the system to then continue the circuit from the blue wire above?)
Yellow/black - runs to the AC switch on the dash / fan switch
Yellow/green - again to the AC switch / fan switch on dash
white/black (think its this colour) - unsure ?
black/white (think its this colour) - unsure?
Yellow - unsure?

Second picture - Red Black - unsure? (power to the clutch possibly?)

Trying to make sense of the system to find out where the break is and the reason I'm not seeing any power on black/red cables in the bay which I've been suggested to that one of them is the clutch power cable

(Continued below to upload more photos)

 

[Ozzy75]

#4 I believe on HJ75's there is a low pressure switch in the ac box under the dash is this correct? does power get sent to this from the AC amp then to the engine bay or?

#5 A friend of mine has a 2H similar ute however he has dual temperature sensors in his top thermostat housing one in the normal position and one slightly higher which he has told me is an AC temp sensor, however I cannot for the life of me find a temperature sensor for the AC into the radiator system anywhere? did all 2H's have this or some not? Mines 1988

vs mine

Hoping someone can dumb down and explain the circuit a little better to me I've tried figuring it out with a wiring diagram unfortunately it doesn't make much sense to me unsure if my AC amp is busted, my low pressure switch is detecting low refrigerant and breaking the circuit or where else to be looking.

I'm assuming it's low on refrigerant as it's sat for the last 12 months not working however wanted to confirm before bringing my ute up to have it re-gassed to find out I need to disassemble it later to fix a sensor of some sort and get it re-gassed again.

Hoping to at least get power to the clutch and then figure out leaks etc to be delt with later.

Thanks anyone for some insight, wisdom and assistance its much appreciated!

Trent

 

[jblueridge]

#1 I ran my ac without the ac amplifier by hot-wiring the ac clutch like you did but running that power through a switch I added in the dash. Eliminates all the complications that are the ac amp. Less than perfect as I had to cycle it on and off by hand but I got used to it. I now have an ac amp that works.

#3 I can't remember all that stuff but there should be a wire or two going to a temp sensor in the ac box (in addition to that low pressure switch wiring). If this temp sensor gives a certain reading and the dial on the dash calls for ac and if the low pressure switch shows there is NOT low pressure, the power is sent to the clutch.

#5 On my 13BT there are two temp sensors in about the same positions as yours. One is dash temp gauge sensor and the other is a sensor for the glow plug or pre-heating system. Neither is related to the ac.

 

[Ozzy75]

#1 I ran my ac without the ac amplifier by hot-wiring the ac clutch like you did but running that power through a switch I added in the dash. Eliminates all the complications that are the ac amp. Less than perfect as I had to cycle it on and off by hand but I got used to it. I now have an ac amp that works.

#3 I can't remember all that stuff but there should be a wire or two going to a temp sensor in the ac box (in addition to that low pressure switch wiring). If this temp sensor gives a certain reading and the dial on the dash calls for ac and if the low pressure switch shows there is NOT low pressure, the power is sent to the clutch.

#5 On my 13BT there are two temp sensors in about the same positions as yours. One is dash temp gauge sensor and the other is a sensor for the glow plug or pre-heating system. Neither is related to the ac.

Thanks for that info mate, so the temp sensor is also in the AC box + the low pressure switch good to know... I might by pass both for now since the clutch isn't hooked up to test see if the AC amp box will then send power to the black/red wire I suspecting is the AC power wire which I'll need to reconnect up to the clutch if that then get's power ill trouble shoot between the two sensors and can eliminate it being the AC amp box... Am I correct in thinking there's just these two sensors that need to be bypassed for the power to continue on ?

Also any idea what wire colour is the power sent to the clutch from the AC Amp box? Odd that red/black one is the same I've found in the bay just slightly smaller in diameter.. or is it sent direct from one of the two sensors ?