When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I bypassed the system on a Mazda mk 2.5 MX5 (Miata) by using a power probe at the compressor plug, had the engine running and fan on, the compressor kicked in, felt the pipes getting cold, but would only do it for a little while as the pressure release valve would kick open which gave me a bit of a fright when it first did it, a change of underwear was needed.
Not sure if that's possible with the Jag apart from the access issues, I think it's all powered differently than most cars in that it's an "always on" system. I think!
Out of interest, where was your leak?, I got my A/C regased last summer and it's gone already, I ran a load of checks myself before I got it regased, I have a manifold but can't get the gas, but the gauges showed the system was empty, so I suspected a leak, I then bought cans of Nitrogen and pressurised the system with that, left it in for hours, with no change in pressure, looked for leaks using dye, and UV light, but found nothing, the A/C guys found no leaks either, and it recharged fine, was ice cold all summer, now we have had a week of hot weather and it's blowing hot air.
Thanks for the reply. I usually jump the clutch/compressor relay which I cannot find or jump the low-pressure switch which in this case is a three wire switch. I don't know which wires to jump. Plus the leak I thought I had identified I miss diagnosed. So for the moment I'm back on the search for the leak.
It is a clutchless system that is always on. The climate control module (CCM) determines the proportion of duty cycle (from 2-100%) required for the temperature setting and cabin conditions. None of it runs on a 12 volt system, therefore supplying 12 volts to force the compressor to activate is not possible as it runs on a pulse bandwidth modulated signal. The pressures transducer (what you referred to as the low-pressure switch) receives a reference 5 volts from the CCM and returns an adjusted signal voltage back that is correlated with the pressure measured in the discharge line
All this to say, the system is difficult to override. Check to see that the square drive 'module' (I don't know what to call it) is spinning with the compressor pulley. If the compressor becomes seized, this object is a sacrificial part that will become divorced from the pulley, preserving the accessory drive belt. If you see it stationary while the pulley is spinning, then the compressor will need to be overhauled or replaced.
This is the compressor. The square thing on the pulley connects the pulley to the compressor driveshaft.
Here is mine removed from the compressor. Normally it is epoxied to the pulley. Mine had sheared as my compressor pistons had become seized.
I think I and, more so, many others have written a great deal about this system. Try and do a search on this forum and you will be rewarded with a lot of information to parse. Good luck with the troubleshooting and repair!
Thank you for a detailed reply. I'll check the compressor; but when I put my gauges on the system, I had 0 PSI. So hopefully a leak is my only issue. I'll report back when I know more. I also read the long thread where you helped the poster with the compressor "O" rings and snapped bolt. Good information there and hopefully not my future.
