Is it true that you must wait for like 2 days and drive 70 miles roughly after replacing the air con pump since the condenser oil has to settle down? Otherwise the gas will leak out since the oil pressure is wrong apparently?

(WHole engine has been replaced and the air con pump, was advised not to refill aircon gas immediately. He said all gearbox oil and engine oil ect all settles down immediately but not condenser oil).

Any advise please, is this true and could you explain more please.

  • The ac system needs to be evacuated prior to filling with freon, have a professional do it.
    – Moab
    Aug 9, 2018 at 22:11
  • What is the year/make/model/engine of the car in question? Aug 9, 2018 at 22:15
  • Peugeot 407. Is the AC "evacuation" the "aircon regas & clean" that they say here for example? mrclutch.com/air-conditioning-recharge Is the clean the evacuation that you speak of?
    – Mark
    Aug 9, 2018 at 22:28
  • I’ve never heard of or seen this in service information.
    – Ben
    Aug 9, 2018 at 23:16
  • But is this stuff about waiting for the oil to settle true???? And if you don't wait it leaks out?
    – Mark
    Aug 9, 2018 at 23:24

1 Answer 1


This is pure nonsense with mobile AC systems.

If you fill the air con pump up with the correct quantity of oil (either a full charge if the system has been flushed, or the same quantity of oil that was drained out of the old compressor if there was no need to flush the system; a flush is always recommended though), all you need to do is to install it on the car and connect it to the piping, and then manually (or with the help of an appropriate tool, with older pumps such as Harrison A6s) rotate the pump's shaft (by rotating the clutch hub in case of a clutch equipped pump, or the pump's pulley in the case of a clutchless pump) 10 times (10 full revolutions) before vacuuming and charging with refrigerant and 10 more times after the system has been vacuumed and charged with the correct amount of refrigerant, and this will make all the excess oil (and any liquid refrigerant that made it to the compressor too) exit the pump's chambers without doing any hydrolock damage as soon as the pump is switched on, since whatever won't (and shouldn't) stay inside the compressor will distribute throughout the system, and, most importantly, the pump will start in a lubed condition.

If you want to be 100% safe you just need to turn the pump on for the first time after replacement only when 1)10 minutes have passed since the system has been successfully charged with refrigerant (to let the refrigerant fully mix with the lubricant oil) 2)the engine is at idle. Then let the pump run for 5 minutes on full AC load (maximum fan speed, and external air flap open; both conditions ensure that the evaporator is on full heat load and therefore the flow of refrigerant and lubricant through the TXV and to the compressor is at its max) keeping the engine in idle.

Right after you put the oil charge inside the pump and before you install it, keeping it in upright position (so that the pulley part is facing down) for some minutes is sufficient to lube the shaft seal. The other seals in the system (o-rings) are instead lubed with non-hygroscopic oil before being put into place.

In most countries, refrigerant can be legally handled only by licensed professionals (and, even when it's legal for everyone, asking a pro to do the refrigerant work is always better because the equipment required to properly service an AC system by refrigerant weight is expensive, and you can damage the pump when you charge the system only by pressure). If you can find a licensed pro who is willing to only care about the refrigerant part (evacuating the system, and then vacuuming and putting the correct refrigerant charge inside; and, if you have the money, full system flush too, since a correct flush requires a closed loop refrigerant machine to be used), you can however do the pump removal, lubing and fitting work yourself (in that case, better use double end capped PAG oil as lube, so that moisture degradation of the oil won't be a problem; let the professional replace the dryer however).

However i can guarantee you on the fact that the oil charge is put inside the compressor (or, if the compressor doesn't need replacement, any other component that has been replaced, such as the condenser or the receiver dryer). The refill station can inject oil too but it's only used to restore the oil that came out during refrigerant evacuation (or add an additional oil quantity, required due to exceptionally long piping, that won't fit inside the compressor; this rarely happens with cars though, it's mostly meant for buses with a separate pump for the driver AC or for construction equipment). Never let the compressor start without any oil inside.

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