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Recharging Ford-Ka air-conditioning

I've just bought one of those Halfrauds kits to recharge the A/C on my Omega, then out of the goodness of my heart offered to top the wife's Ka3 up (it's considerably less effective [cool] than it has been in the past).

Now...

The kit says to check the low-pressure port with the engine / A/C running, however on the Ka this shows a low-ish (20psi) ramping to high-ish (60psi) over a 2-3 second period, then there's a click "down-below" which dumps the pressure back down to 20psi where the cycle starts again.

The kit says only fill if the A/C pressure is less than 25psi, which confuses me as the pressure varies above and below that pressure.

The static pressure with the engine / A/C off is about 70psi ("in the red", according to the pressure gauge), but the instructions said nothing about the expected pressure when A/C is off.

So, anyone with any experience of these things?, care to explain the system (the cyclic dumping of pressure), and who knows whether this needs recharging or not?

Regards

Mike

Reply to
Mike Dodd
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Are you sure you are connected to the LP port?

Static pressure should be around 60psi (on a properly chraged system) which would drop to around 30-45psi with the compressor engaged.

(very approximate values)

You cant have more pressure on the LP with the comp running than with it stopped!

Tim..

Reply to
Tim (remove obvious)

Aha, that'd be the 70psi with the engine / a/c off bit of the description. It does sound like the system might be a little overcharged.

The bit that is confusing me is the apparent cycling of the compressor when the A/C is running.

Reply to
Mike Dodd

I think you'll find they all do that. I've never known one that doesn't. Mike.

Reply to
Mike G

The compressor doesn't run constant or the entire system would freeze over. It runs for a while then an electronic clutch in the compressor pulley disengages until an internal temperature is reached, which then starts the compressor again.

Reply to
Sandy Nuts

No, not really.

The clutch is at the mercy of a temp sensor in the intake plenum of the heater which is set to ~4deg c (on non climate control equiped cars) and the system strives to reach this temp, at which point the clutch is released.

On a cold day it may reach 4 deg and the compressor shut off fairly easily. On a hot day it may never reach it so the compressor will run continuously...

Tim..

Reply to
Tim (remove obvious)

Can't argue either way... The Ka seems to cycle, the Omega seems to run continuously. Any chance that there are two systems out there with different strategies?

Still leaves me in a pickle as to how to measure the dynamic low-pressure on the Ka, since it cycles too quickly. Certainly isn't as cool as it should be, or was after the last re-gas, but after a re-gas, surely the pressure can only drop over time - so any loss of efficiency over this period can surely only be as a result of coolant loss?

(wondering about the accuracy of the pressure gauge on the filler)

Reply to
Mike Dodd

Try putting the heater on max, fan on pos 3, on recirc and warming the interior of the car up pretty hot, then engaging the AC. It will stay engaged for alot longer and you may be able to get a more sensible LP reading...

Tim..

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Reply to
Tim (remove obvious)

Hmmm, thought the Ka A/C was open loop?

Bit the bullet and dumped a can in - the more gas I added, the slower the cycling became, now its ~ 30 seconds or so, and the A/C temperature is much lower in the cabin.

I did read up more on the cycling thing... 5 seconds does appear to be ridiculously quick and could cause excessive wear on the clutch. Having read more, and observed the system in operation, I believe that the clutch disengages when there's insufficient pressure in the system. Having disengaged the pressure on the low-pressure side starts increasing as the system normalises and the clutch kicks back in.

Reply to
Mike Dodd

Hi Mike

I had exactly the same thing on my Mondeo. Circa 20PSI isn't sufficient pressure, so the compressor disengages to protect itself (as not enough gas).

This causes the Low Pressure side of the system to increase in pressure (Compressor off). Hence the higher reading (60-70PSI). After a short period, the compressor has another go, and the cycle starts over again.

Fill it up with gas - this will certainly help to solve things - the cycling period will become shorter as you pump the R134A in. Once it's fully topped up (say 40-45PSI), the compressor should run more-or-less constantly, with only a few engage/disengage cycles.

Hope this helps

Best,

Alan

Reply to
Alan Dempster

Thanks, that's exactly what I wanted to hear.

Reply to
Mike Dodd

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