I have replaced the air compressor (which came oiled from factory), condenser, evaporator, and expansion valve on a 2002 Honda CRV. I also replaced the alternator.

I want to turn the engine on to make sure the car is running properly, sans AC, and that the new alternator is working properly too. I am going to take the car to a shop to have it vacuumed down and recharged/re-oiled, but in the meantime, will running the engine without refrigerant and oil in the rest of the AC system ruin the compressor or any of the other components? This is assuming I leave the AC switch off on the dashboard. Also, I'd want to drive it to the mechanic to have it vacuumed and recharged as well and don't want to ruin the new compressor.

I just can't find any definitive information online about this and don't want to ruin all the work I did and money I spent.

Thanks in advance!

  • Welcome to Motor Vehicle Maintenance & Repair! Commented Feb 19, 2022 at 17:12

2 Answers 2


Your compressor should be clutch driven. If so, then running the engine won't do it any harm. The clutch won't engage the compressor without a refrigerant charge present. With the pressure at atmospheric, the pressure switches which control the system won't be tripped and allow the compressor to run. You should have no fear of running your engine without a charge present.

  • How recent is this development? My 2003 Volkswagen Jetta did fry the compressor after a refrigerant leak. Commented Feb 21, 2022 at 0:37
  • @chrylis-cautiouslyoptimistic- Was the clutch locked up in your compressor? If so, this could have caused the leak (over working the system), and then would allow the compressor to get fried in the process. We are talking about a new compressor with a new clutch in the OP's case, which is HIGHLY unlikely to occur. Commented Feb 23, 2022 at 13:22

some cars will automatically turn the A/C on when the defroster is turned on because it takes frost or moisture off the windshield faster. I do not know what your car will do. So beware.

  • Welcome to Motor Vehicle Maintenance & Repair! For your situational awareness - while you are correct the defroster can turn on the A/C to remove moisture, it won't turn it on if the system is not charged. It functions the same way as if put on A/C to cool the air and won't engage if there's no charge present. I didn't downvote your answer, but your answer really isn't relevant in this case. Commented Feb 23, 2022 at 13:19

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