Aircon not cold!

Discussion in 'Technical' started by Leaf Meister, Sep 13, 2016.

  1. Leaf Meister

    Leaf Meister New Member

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    Hi all,

    AC crapped itself on my Z. My climate control are the early model auto ones. Blower works fine and responds to hi/lo settings accordingly. Heater also works and warms the car up fine. But no cold air!

    Suspected it could just need a regas as I've recently only bought the gas and the previous owner just mentioned he had it regas but no proof. Took it to a AC shop near my work and they took a look, said it had no more gas. They did a test for leak and could not find any leak so went ahead and regassed.

    Eventually they diagnosed that the ac compressor wasn't running and they suspect the air con amp is faulty. They bypassed it with a switch and ac runs. It is a 'band-aid' solution in my opinion and I'd like to fix the issue properly.

    Are the AC guys I went to correct in saying the amp is definitely the cause? Because they have quoted me to take dash out and replace the amp (big labour $$$)!!! What I don't understand is that (if previous owner did get ac regassed) how come it ran out of gas so quickly? Surely there must have been a leak somewhere but AC guys I went to can't find it? Perhaps there is another solution to this problem - what are other possible causes for no cold air?
     
  2. East Coast Z

    East Coast Z Well-Known Member

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    Obviously if the system required re-gassing, there is leakage.
    Because it can't be found, doesn't mean there is no leak.

    It's the same deal with the tyres on your car.
    You can set the pressure to a certain value & over time the pressure will reduce.
    You won't find a leak, but the air in the tyre is leaking out.

    To assist with leak detection, a dye can be introduced into the aircon system.
    The dye leaves a residue at the point of leakage which can be seen under UV light.
    Perhaps the leakage is located in an area that is not visible.

    As far as the amp being defective, it's probably possible.

    I'd be looking at the wiring circuit & seeing what has actually been bypassed with the installation of the switch.

    Could it be something else?
    That's also probably possible.
    As an example, the engine ECU also has control over the aircon.
    The ECU receives voltage signals indicating if the aircon is on or off.
    If the aircon is on & you plant your foot, the ECU turns the aircon off momentarily to provide full engine power.
    It also turns the aircon off if the engine temperature is high.
    Perhaps there could be a problem in this area?

    It may be advisable to have a read through the Air Conditioning Section of the Nissan Service Manual, it's pretty heavy reading, but you will gain an insight as to how the system works & how to diagnose problems.

    It may also be advisable to check out posts on the forum relating to heater core replacements performed by members, it will give you an idea of what's involved in removing the dash etc.
     
  3. stumagoo

    stumagoo Active Member

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    as above , there are some other things to look at, make sure the clutch on the pump is indeed clicking on when AC is turned on. there are other things in the system that can stop it turning on as well.
     
  4. Leaf Meister

    Leaf Meister New Member

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    Thanks East Coast Z, have tried to follow the online manual for AC but there's so many things that I'm lost at where to start. Since the auto electrician has said that he found no signals being sent from the AC computer to get the compressor running, it very much seems like the AC computer is dead?

    I was told by a mechanic who has experiences with the 300ZX and took a quick look at the car for me:" The computer doesn't actually have any way of telling the AC isn't working except the pressure switch's which were all giving the correct signals. "

    From what I've read online, I've seen people mention the ECU does have access to the AC. Is this something I can run a check/diagnosis through the consult? I do regularly check for error codes (twice a week at least) as I have a bluetooth adapter in it so its easily accessible from my phone. Always showing a code 55. Conzult program doesn't seem to like me and won't work though so I mainly run Nissan DataScan. I do monitor water temps and even have a digital water temp gauge - always showing 73ish degrees in Perth weather now ( ambient 12-20 degrees whenever I'm driving) which I was told was normal?

    @stumagoo what's the best way to check that the clutch is working? I do hear that click now that the switch has been installed (didn't before when I pressed auto). Which points to AC computer as the issue?
     
  5. TWIN TERROR

    TWIN TERROR Well-Known Member

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    :rofl:Shouldn't be to hard to trouble shoot with a multi meter.
    * I would personally check 3 first :D
    1 - If you have a temp display is it ready correctly (the cabin air temp). Sensor is mounted in the roof between targas from memory.
    2 - Check A/c fuses.
    3 - unplug wire at compressor and switch on a/c the check for + 12 volt d.c power (compressor is more than likely earthed to motor). If you have power then the compressor or compressor clutch is faulty. If no power look elsewhere.
    4 - If no power check a/c compressor relay.
    5 - Check pressure switch.
    6 - Check gas as if some are low a/c compressor will not turn on. If low you have a leak then it needs fixing before re-gassing. If you re-gas without fixing the leak you will have to re-gas it again when it runs out again. (not rocket science).
    7 - This is for dick head points - YOU DO HAVE A A/C BELT :rofl:
    Cheers
    Dave
     
  6. East Coast Z

    East Coast Z Well-Known Member

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    "the auto electrician has said that he found no signals being sent from the AC computer to get the compressor running, it very much seems like the AC computer is dead"

    I'm not by any means an air conditioning technician, but this sounds sus to me.
    If the AC computer is dead, you won't be able to adjust blower speeds, temperature or the doors to direct airflow.
    I'd be very interested in knowing more about this switch the auto elec has installed.
    Could you possibly let me know where it is & the colours of the wires connected to it?
    We'll trace it on a circuit diagram & figure it out.
    The AC computer can be accessed via ConZult, but not the free version.
     
  7. stumagoo

    stumagoo Active Member

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    the click is the first give away, on some cars you can actually see the centre of the clutch move (and start spinning). if you can verify the clutch is engaging on the compressor then that is all that the compressor needs to run - this should coincide with an increase in engine revs for the extra load when idleing, which tells you the engine ecu is getting signal and doing the right things. if at the correct temps the aux fan should start as well. of course if bypassing the ac computer then this most likely wont happen.
     
  8. tassuperkart

    tassuperkart Its a lie I tell you!

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    Stay away from them.
    Takes about 20 minutes to swap those AC computers over.

    Id be looking at fuses and relays. There are 2 fuses and a relay in front of that AC comp clutch.

    E
     
  9. QLDZDR

    QLDZDR ID=David

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    I'd like to know about this band aid switch the auto electrician put on.
    Sounds like a good bypass trick.
     
  10. stumagoo

    stumagoo Active Member

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    I imagine it is manually triggering the AC clutch.
     
  11. Leaf Meister

    Leaf Meister New Member

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    Ok, loving the advice so far as that gives me a whole list of things I can check out and hopefully avoid getting ripped off anymore.

    First issue I need to resolve before going further is to get my hands on a new AC compressor. I was driving and using the AC (via that bypass switch) and next minute belts sound was very loud followed by my revs taking a plunge to the point the engine stalled. Tried starting the car up a couple times and it just clicked over - battery was killed. Took it to a mech around the corner who offered to raise it up on the hoist and have a look for free (spent too much money here previously so he felt obliged :bash:) within a few minutes he said the AC compressor is definitely seized - he can't do much regarding the possible AC computer crapping itself as AC compressor isn't even allowing AC to come on for more than 20 sec before stalling the engine.

    Over the weekend I quickly checked the AC fuses in the driver footwell. None are blown and pulling them out then attempting to operate the AC pod results in nothing so I assume the connection there is just fine and fuses are doing what they are supposed to. East Coast Z mentioned that can't be AC computer due to blowers being able to go hi/lo which is the case. Temp accuracy on the pods seem ok as it was showing 14 degrees AMB this morning and weather report is saying 13 degrees. My pod is the S1 digital j spec one so I can't exactly control air flow to feet/doors/etc. But the demister, REC settings all do their job and direct airflow respectively.

    Essentially, that switch bypass allowed the compressor to work again, thus giving me cold air but it seized within a few minutes of operation.

    Could it have been operating without stopping at all?
    Not very knowledgeable on AC but isn't the compressor like fridge ones that only come on periodically when needed?
    Was mine just running non stop in that 20-30min time frame it was operating and finally seized?

    Method of operation after this bypass switch is to turn AUTO on which lets the blowers kick in but no cold air, then flick that bypass switch which lets the AC compressor come on and cold air! Will try to get under the car once I get time but hopefully this helps paint a better picture.
     
  12. tassuperkart

    tassuperkart Its a lie I tell you!

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    Not quite the case with the Zed.
    AC comp comes on and pretty much remains on as the Zed employs a suction side throttling valve rather than cycling the comp on and off in response to evap. core temps.

    From what Im reading here are you saying you can/have run the system for short periods of time subsequent to the comp seizing the first time???

    E
     
  13. Leaf Meister

    Leaf Meister New Member

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    Correct - so after the auto electrician did that switch bypass, AC was 'working' for some time. By working, it means I have to turn AUTO on the AC pod for fan blower to come on then flick the bypass switch to get compressor going because apparently AC computer wasn't doing its job.

    I had this setup running for short periods of time of roughly 5 minutes each time for about 4 or 5 times over a 2 day period before AC compressor seized up and stalled my engine. Had to jump start the car and go buy a new battery to replace - never dared touch the AC again after that as the mech who took a look said its definitely seized and will probably stall the engine again:(
     
  14. TWIN TERROR

    TWIN TERROR Well-Known Member

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    Get an a/c guy to check some dick hasn't over gassed the system :D. It's knot rocket science you just need to now what you are doing.:eek: Ask around the local bar as fridgie's love beer and a slab will get you a fair way
     
  15. tassuperkart

    tassuperkart Its a lie I tell you!

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    Hahah yes that too ^^!!

    My bad, i got the impression that the system was working AFTER it seized the first time.

    Its pretty hard to mis-diagnose a seized compressor so id say thats the case and id also suggest that the AC system has had a failure at some point and lost its gas, and most of its lubricating oil together.
    Some dude does a quick repair, gets it gassed up, gasser probably doesnt know the system was blown prior, doesnt add lubricant as a matter of course and you can guess the rest.

    E
     
  16. Leaf Meister

    Leaf Meister New Member

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    I guess before anymore troubleshooting can continue - I need to get another compressor to replace this seized one.

    Mechanic thinks he knows a guy who can rebuild my seized one. From what I've read online though, seems like a 'rebuilt' compressor is barely ever reliably rebuilt and often results in issues. I would go with new but the only new AC compressors I could find for 300zx are the ones sold by Z1 and Concept Z - however it does say for LHD only.

    Does anyone know if the US compressors will work with my jap import? What sort of modifications required to make it work? It isn't cheap at all so I'd like to know for sure that it is somewhat compatible before pulling the trigger
     
  17. tassuperkart

    tassuperkart Its a lie I tell you!

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    Mate, if an AC compressor is siezed, thats the way it will stay. That assumes that the compressor innards are actually seized and not just the pulley bearing which can be easily replaces.
    Altho they can be stripped down and rebuilt, its never worth the time and money and replacement parts are just not available for them.
    The best that can happen is a pulley bearing can be changed and a shaft seal put in and perhaps a few end housing seals.

    A compressor from just about anything can be made to/adapted to fit if you have some facilities!!

    E
     
  18. QLDZDR

    QLDZDR ID=David

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  19. STocKi

    STocKi Member

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    Hey leafy,
    Looks like I've got the same problem as you. Everything works on the control pod except turning on the compressor :bash: ...and mine's a S2 pod

    I'm going to try and trace this 'negative' switch signal this long weekend..
    If your not doing anything....:D:D
     
  20. geron

    geron National Petroleum Equipm

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    Just to clarify...
    So, if ALL the gas has escaped, the AC clutch does not engage?
     

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