RPM surge when A/C on

[Baal]

Hey folks I'm just asking for a second opinion on that one, because I've hit a dead end here.

So here's the thing, when I turn the A/C on, rpms are normal (800) for a few seconds, after that my car starts idling at 950 rpm sometimes even at 1000 rpm.

I've cleaned my throttle body valve, EGR valve, checked the engine for vacuum leaks, (there are none) replaced the alternator regulator, nothing worked so far. Any clue on what could that be?

Volvo V60 2011 2.0 D3 - D5204T2

[sewageman]

Hi,could it be the extra load required to maintain battery charge?

[Whyman]

Or even the extra load to run the ac once it has got going.

[Baal]

I doubt it, the car shakes like crazy. I don't think Volvo would make a car that shakes like that. I'll try to change the belt, (it's a stretch one) I have it in the car somewhere which I bought a year ago and still didn't change it.

Oh and the car does it only when it's hot outside.

[Bashy]

All the cars i have had increase the revs slightly when the compressor kicks in, apart from this V70 D5 185 that i have now, also i dont hear it kick from inside the cabin either like my other cars too, yet it works great. just a guess, perhaps the alternator is not working 100% and it needs the extra revs to compensate?

[Baal]

Originally Posted by Bashy

All the cars i have had increase the revs slightly when the compressor kicks in, apart from this V70 D5 185 that i have now, also i dont hear it kick from inside the cabin either like my other cars too, yet it works great. just a guess, perhaps the alternator is not working 100% and it needs the extra revs to compensate?

Yes I know that when you turn the A/C on, rpm increases from 700 to 800

Maybe the alternator is a little tired already, but it charges just fine 13.8V to 14.1V

[moes80]

Originally Posted by Baal

Yes I know that when you turn the A/C on, rpm increases from 700 to 800

Maybe the alternator is a little tired already, but it charges just fine 13.8V to 14.1V

Hi Baal,

Hope all is well (other then the revs issue ).

Thinking about the above....does the ac cool? as in is it actually working?

If yes, then we know the refrigerant path is clear, so what I'd look into is the compressor bearings (assuming there is such a thing), maybe compressor is on it's way out or needs a overhaul, as something is taking that little bit more for the engine to rev up. Have a look at the belt tension, maybe when the ac kicks in the belt slips.
If ac not working, then there could be a blockage in the system.

I'll keep thinking...you keep checking

Kind regards

moe

[Baal]

Originally Posted by moes80

Hi Baal,

Hope all is well (other then the revs issue ).

Thinking about the above....does the ac cool? as in is it actually working?

If yes, then we know the refrigerant path is clear, so what I'd look into is the compressor bearings (assuming there is such a thing), maybe compressor is on it's way out or needs a overhaul, as something is taking that little bit more for the engine to rev up. Have a look at the belt tension, maybe when the ac kicks in the belt slips.
If ac not working, then there could be a blockage in the system.

I'll keep thinking...you keep checking

Kind regards

moe

Hey moe. The compressor is new HELLA unit I've replaced a couple of days ago, the A/C is blowing freezing cold air almost got hypothermia yesterday

I'll change the belt and report back. The belt doesn't even need to slip for this to happen, the old age is the main factor here.

[Baal]

Changed the belt, changed all vacuum lines, still surging.

Ideas anyone?

[moes80]

Originally Posted by Baal

Changed the belt, changed all vacuum lines, still surging.

Ideas anyone?

Hello Baal,

Not sure if any of this is going to help or even make sense as I'm typing what I'm thinking

We know the AC works, we also know the compressor and belt are new. The engine revs up because the electronics are telling the engine of the extra load.

I would disconnect the compressor at terminal level and switch the ac on. Obviously, the ac will not work because the compressor has been disconnected, if engine still revs up then it's an electronics issue (programming). If engine does not rev up then it's something to do with the ac setup. Next thing I'd look for is all the inputs from the AC system. I would have thought the revs are related to the alternator charge rate, so check the alternator output is sufficient in both cases AC on and AC off. Also worth noting when the AC is on the fan is also on, that could be another thing to look at.

What I'd also try is switch everything on excluding the AC to try and increase the load on the engine...see if the revs behave in a similar manner.

no help at all????....still thinking