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1996 Lamborghini VT 2wd, 1994 Ferrari 348 Spider
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Discussion Starter #1
The air conditioning compressor on my 96 (134a) Diablo does not kick in unless the defroster button is pressed. Have gone through electrical system as best I can and have not found any obvious candidates as to why. Found Freon to be very low this spring and added (3) 12 oz cans. After 1 can, the pressure on the suction side came up to 25 psi, but the 2 additional cans did not bring it up any further. Because comp does kick in on defrost setting, suspect there is not a problem with pressure switches in dehydrator or thermal sensor on evaporator outlet. I checked the pressure with 2 different gauges and both say the same thing. The manual says the older Freon 12 equipped cars took an 800g charge and I am pretty well up there. Am concerned about adding more. Am getting lots of cool out of vents at this point however. Any idea how much Freon these are likely to take? Any thoughts on why the compressor won't engage in the air conditioning mode?
 

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Well if your getting cold air the compressor is working, it may be the climate control unit itself. I had to replace mine with very few miles.
 

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1996 Lamborghini VT 2wd, 1994 Ferrari 348 Spider
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Discussion Starter #3
Two control units

There appear to be 2 different units that I am suspicious of and am do not know how to determine the unit at fault. The first is the push button unit on the dash and the second is the ECU located under the pneumatic valves that control the vents. It appears that the push button unit controls the ECU and I have no idea how to trouble shoot to find out which one might be the problem. Any ideas?
 

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That's a tough one. If you cannot re-direct the air with any of the push buttons, I think I'd lean toward the ECU, but never heard of a problem with it. Does everything else about the climate control work? Temp adjust?
 

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Get a hold of one of the units and swap, process of elimination unless you have specific training for these things. It is not the quickest way to diagnose a problem but it is effective. $.02
 

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1996 Lamborghini VT 2wd, 1994 Ferrari 348 Spider
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Discussion Starter #6
Air Conditioner Control Panel

Everything else relative to the heating and air conditioning system control seems to work. I can control vents, fan speed, I can reset the temp and in the defrosting mode, I can cut off the heat so only cold air comes out. I can switch between degree C and degree F.

I believe that substituting components would help diagnose things, but am not sure how to get a component to substitute.

As I have the entire dash out of the car, access is not at this point a big problem. I was going to power up the switch box using the power inputs indicated on the schematic and read out the outputs as I push various buttons, but am not really sure what I am looking for. There is no listing for the lead that controls the compressor on the schematic, but there are listing for many of the other functions. I assume that the compressor lead should be energized for both the Max cold setting and the defroster setting.

I have also put 30 oz freon in the system as it was low. The low pressure reading does not want to rise about 25 psi (checked with 2 gauges). I do have lots of cold and and show no leaks with the die. Does this seam reasonable? Seems like a lot of freon to me.

Thanks for the help.

Paul
 

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Well sure, get hold of an extra is ideal but..... :) I think I'd rule out the climate control itself and look to what controls the vents. A motor maybe?
 

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1996 Lamborghini VT 2wd, 1994 Ferrari 348 Spider
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Discussion Starter #8
Air Conditioner

The vents and relays do not appear to be a problem. All respond when I pust the buttons. The only issue is that power does not go to the air conditioner clutch when in the air condiitioning mode. It does however go there in the defrosting mode.
 

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The vents and relays do not appear to be a problem. All respond when I pust the buttons. The only issue is that power does not go to the air conditioner clutch when in the air condiitioning mode. It does however go there in the defrosting mode.
Do you know the tech at Lambo Ohio? He is a good friend of mine if you want to have him look at it. Just let me know and maybe you can run it by him without taking it to and running it through the shop. Let me know I have his cell number and I will make a call for you.
 

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1996 Lamborghini VT 2wd, 1994 Ferrari 348 Spider
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Discussion Starter #10
Don't know any of the folks at MAG. Have had work done on my Viper at what was Lambo Ohio (aka Nelson Autogroup) in Marysville, but that was several years ago and they no longer represent Lambo in Ohio. Am considering taking the control to George (Evans Automotive). Would rather not put car back together until issue is resolved. Never hurts to have another contact. Thanks.
 

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Climate control

Curious if you ever figured out your initial problem? I'm working on a 25th anniversary Countach with a very similar issue.
 

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1996 Lamborghini VT 2wd, 1994 Ferrari 348 Spider
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Discussion Starter #13
Dug though my old maintenance records and see that I took it to Evans Automotive here in Columbus and they diagnosed the problem as a bad fan switch which when replaced, solved the problem.

PM
 

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1996 Lamborghini VT 2wd, 1994 Ferrari 348 Spider
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Discussion Starter #15
Not sure where you are in Australia, but for the most part I would think that would work fine for you. Good luck.
 
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