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#46
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Re: Possible aircon problem?
I would agree with Trevor about sensor issues.
A fair amount of the cars imported from Japan tend to have air con issues which for no reason just "fix" themselves after a period of time or no fault has been found by air con specialists in the system itself even after re-gassing. Nissan are the main ones with auto climate control, I have found a couple will only go to full heat setting when auto is selected no matter what the temp & will not turn off. 2 skylines have been down to the cabin air temp sensor. I presume the SVX will have 2 sensors for cabin and outside temp that will send info to some sort of control unit? Would it be possible to try to clean/dry them out with a hairdryer to test temp? My thinking is the outside temp should show up in the car & the cabin sensor should then have a high enough reading to kick the air con in if in auto mode?
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11/94 SVX Alcyone, Mica Black, VL Spec 4WS, 71K Miles, 1 owner from new & was part of a private car collection in Japan. Nissan R34 Skyline Stagea 91 Lotus Elan SE Turbo 1966 MGB Roadster, Tarten Red, Wire Wheels, Leather, 23K miles from new You can tell the men from the boys from the speed of their toys. |
#47
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Re: Possible aircon problem?
Trevor, Darren, my picture previously shows why the physical damage I had on the board led to my suspicion that this capacitor was at least one of the causes of this difficult to diagnose and resolve fault.
Having replaced the capacitor [I'm sure it is electrolytic Trevor, I have retained the old one and will dig out specs for you when I can find it] and not cured the problem my next port of call must be replacing or fixing the acid damaged tracks on the board. However as Roger's board shows no damage in his picture I could be barking up the wrong tree. Unfortunately I don't have the wiring schematic for this unit, or don't even know if this is shown in the WSM. [I strongly suspect it may show inputs and outputs and connectors, without showing a circuit diagram for the control boards] However, one question comes to mind in relation to Trevor's and Darren's line of reasoning; assuming or accepting the cause is related to sensor issues, then how do you explain it if the control unit that is faulty is replaced with a known working unit, and then proceeds to work OK? Most if not all people who have fixed the problem in the SVX have had this experience. Does this not imply the fault is within the control unit? I do accept that the cabin temperature sensor is actually installed inside the unit [there is a tube feeding the unit air from the slotted holes in the dashboard] and in replacing the control unit you are actually replacing at least one sensor as well. Also with the SVX control unit it needs to be taken into account that when the box loses its marbles invariably the outside temperature display goes ga-ga and starts blipping, beeping and blinking. A new and working control unit will obviously not replace the outside sensor, but yet will appear to operate normally. I've not so far heard of anyone replacing a control unit and the outside sensor. So is this symptom of failure relevant? Assuming for the moment that possibly my boiling capacitor is a one-off situation and not the normal cause of the problem, can anyone suggest how we might go about testing the temperature sensor? Joe [Oh, and Roger, the + and - things you mentioned earlier are not switches. I think you are referring to the bulb holders for the lights for the panels ]
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Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea Candy Purple Honda Blackbird Plum Dangerous White X2 RVR Mitsubishi 1800GDI. Vantastic 40,000 miles Jersey Girl |
#48
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Re: Possible aircon problem?
The readings of the sensors can be read with a subaru select monitor, or a laptop. You can compare them with an ordinary thermometer. The sensor might not match the thermometer exactly, but if you took several readings at different temperatures you should be able to see whether they follow the same trend. If you still have the old serial cable I sent you, I'll talk you through how to do it.
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Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II |
#49
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Re: Possible aircon problem?
Thanks Phil. I do have it but I'll have to dig it out. It's in a pretty crowded [aka chaotic] part of the house.
I've actually stripped out the sensor from the control unit and photographed it. It's just an ordinary thermocouple connected to one of the 3 boards by two wires. I'll upload the photos when I get them onto the PC. It does not seem to be obviously broken, but you never know. Arthur seems to think an intermittent reading could lead to this problem. Joe
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Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea Candy Purple Honda Blackbird Plum Dangerous White X2 RVR Mitsubishi 1800GDI. Vantastic 40,000 miles Jersey Girl |
#50
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Re: Possible aircon problem?
Joe,
I say again, have you run an air conditioning diagnostic system, as per manual 4 - 7 - 4. ? The sensors can be checked aa per the manual instructions, using an ohmmeter and thermometer and is not difficult. My money remains on an intermittent sensor or circuit, first the in vehicle/cabin, then the external ambient and least likely the sun-load photo diode. I am now wondering if your UK cars are different from my JDM. as is covered by manual Publication No. G301RE(4) Feb. 1992, details on back cover.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#51
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Re: Possible aircon problem?
Joe - ref the + & - switches I mentioned. The round temperature setting control is effectively a rocker switch. It has lugs top and bottom which press small black (about 5mm square) switches attached to the circuit board. The top one for increase in temperature and the bottom one to decrease it.
As the most common problem is that, when faulty, the temperature counts down to 18, or as sometimes reported, up to 26C - would it be too much to suspect that the switches could become faulty?? Could the switches just be sticking? The fault is very similar to someone holding the switch down (or up). Joe, I'll try to get you the photos of the other side of the circuit board when I get a minute or two. I'm really pleased that there is a good focus now on this irritating problem. |
#52
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Re: Possible aircon problem?
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#53
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Re: Possible aircon problem?
Joe, I just noticed the new post. What you have is the same debris I had from hand soldered joints, they have not cleaned off the flux. I dont think it is anything leaking from the capacitor. On mine the hand soldered interboard connector cables has the flux debris on several of them, I think it has simply formed a conductive bridge and depending on the location different faults will appear. Having said that although the problem reappeared on mine, it has been OK for several months now.
Become an expert on fluxes (but dont mention it when out drinking!) http://www.residues.com/faqs_fluxes.html |
#54
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Re: Possible aircon problem?
Just noticed the last post about switches - they may well be hand soldered have a look for the flux debris, it could well be the cause of the short circuit.
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#55
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Re: Possible aircon problem?
I just found this on a Japanese SVX forum. Doesn't help the problem but it's interesting none the less.
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Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II |
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