QuestionHi,
I have a 2000 Merc. Sable. I have noticed a surge or slight jump,in the motor when I'm driving,idling or in park, when the heat or ac is on. You can actually see the rpm jump slightly. I took it to a mechanic and he said he thought it was because of the mileage on the car(or maybe he meant the compressor)??? My husband and I didn't think that sounded right and wanted a second opinion. It has not been cooling like it should and my husband says he thinks it surges because it needs to be gased up. Thanks,in advance for your help and for pointing us in the right direction.
AnswerDonna,
When you turn the AC on you should see the RPM's drop about 200 and then come back up. That is normal. Just the engine compensating for the extra load. It shouldn't do it when the heater is on, unless you have it set for the defrost setting. (That setting engages the compressor also) Everywhere else, it shouldn't do anything. I'm not sure what you mean by surge. Does it go up and stay there, or back and forth?
Regardless though, I am inclined to believe that the issue is completely seperate from your AC/Heat. Being low on refrigerant would not cause this at all, because the compressor would not be engaging if it was too low.
I would have your mechanic look into the vehicle further. I am sorry that I am not an engine tech, or I may be able to help you more. But If you look under the other categories, I am certain that there is a Mercury expert that will be able to assist you.
But again, I am fairly certain I can safely steer you away from the heat/ac systems.
I hope I was able to assist you at least a little bit. If so please remember to rate this answer. If I can do anything further now or in the future, please do not hesitate to ask. Good luck in everything and take care.
