Rear A/C capped, now A/C cycling

[white_lx]

Thanks to the road salt the lines to the rear A/C rotted out on our '00 LX470. Last night I capped them inside the hood. Pulled a vacuum and recharged.

Today the A/C is cycling intermittently. Comes on for about 2-3 seconds and then switches off. It keeps doing that. When cold the off times seem seconds, when the engine warms up it can be off for long times before the A/C kicks in again.

Any ideas what can cause this? When the A/C kicks in the rpm goes up, but it goes down as soon as it switches off again.

Is this an electrical issue? Don't really know where to start.

Edit: did some research: could this be the triple pressure switch switching off the A/C? Maybe caused by saturated desiccant, resulting in the expander valve freezing up? Any suggestions where to start looking?

Thanks

 

[vogs77]

Sounds like you over charged the system. How much refrigerant did you use without the rear system connected?

 

[white_lx]

Sounds like you over charged the system. How much refrigerant did you use without the rear system connected?

Thanks for your suggestion. I'm not an expert, but I think I did it right. I used (borrowed) gauges and filled it to the correct pressures - both Hi and Lo as per the service manual.

Everything seemed to work fine the night I filled it. Than it started to act up the next day. In the morning it was fine, but on the ride home it started cycling.

I will see if I can borrow the gauges again. But since it now only runs for about 1 sec, it is hard to determine pressures during AC operation.

 

[Kigiin]

I had a similar problem after removing rear lines and re-sealing system. The air would blow cold, then hot, and then cold. My mechanic had a theory that after removing the rear lines, the capacity of system was reduced and had been overcharged. Reduced charge and all has been fine for over 7 years.

 

[white_lx]

Thanks for the suggestions. I decided to ignore the pressure gauges and remove some refrigerant. That did the trick. I'm so happy to have A/C back in this vehicle.

Btw: I used 3/4" and 5/16" stainless steel Yor-Loc compression fittings from McMaster, since I was unable to source any specific A/C caps locally.