Engine idle not increasing or decreasing with AC...

[Wara Waghi]

Hi,

Need help here. My AC decided to stop. Visited a service guy. We changed the compressor, the condenser, cleaned the pipes and burnt the compressor in doing so....now compressor fixed, but the engine idle does not seem to go up and down with the ac turned on....it's a VDJ79 series trooper...what have we missed?

 

[Shayne]

Idle only ups to cope with the extra belt driven load , AC is all new so turning freely and offering little resistance . I'd not be worried at all .

I guess your old A/C being knackered put up a fair bit of resistance so increased revs to cope and now it seems something isn't quite "normal" .

 

[Towpack]

On a 80 series the idle up is triggered electrically when the AC is operating (pump clutch engaged) and a vacuum actuator opens the throttle slightly. It's not an "intelligent" setup" with any sort of load sensing, it's purely on/off. The power steering idle ip works in the same way.

 

[Dave]

Probably has a variable displacement compressor, not the old style on/off, so the engine management takes care of the load and keeps the idle stable. One of the complaints of the old compressors was the banging on and off and engine surging.