Thread: Rough Idle with Air Conditioner on TD5

Do you have any voltage drop issues. For example is the fuse block under your seat melted where the main power lines feed in? Can you get the same issues with the heated rear screen and lights on etc? The ac draws a fair amount of power so wondering if its a voltage drop somewhere.

Originally Posted by BilboBoggles

Do you have any voltage drop issues. For example is the fuse block under your seat melted where the main power lines feed in? Can you get the same issues with the heated rear screen and lights on etc? The ac draws a fair amount of power so wondering if its a voltage drop somewhere.

Fuse box under the seat sounds like a Defender thing.

I did notice voltage was only 13.9 to 14 volts. Air Con didn't seem to make much difference to the voltage at the Nanocom or Aux Battery gauge.

Measure the voltage directly on the compressor clutch's plug(black/green wire is live) while somebody switches on and off the aircon....if it's a noticeable drop when switching on the clutch/compressor might be sticking and the engine must work harder to turn it and that's the reason for the idle thing

also you can remove the compressor clutch relay(R11) while aircon is on and se if the symptom completely dissapears or not, cos if when you remove the relay everything gets back to EXACTLY like when the aircon is switched off then the problem is there somewhere with the clutch

My rough idle with A/C on ended up being engine mounts as well.

Originally Posted by sierrafery

Measure the voltage directly on the compressor clutch's plug(black/green wire is live) while somebody switches on and off the aircon....if it's a noticeable drop when switching on the clutch/compressor might be sticking and the engine must work harder to turn it and that's the reason for the idle thing

also you can remove the compressor clutch relay(R11) while aircon is on and se if the symptom completely dissapears or not, cos if when you remove the relay everything gets back to EXACTLY like when the aircon is switched off then the problem is there somewhere with the clutch

I tried pulling compressor clutch relay (R11) and while it was not hot today there was no repeat of the rough idle.

Looks like I'd better have a look at the Air Conditioner Clutch..

Originally Posted by mousie

My rough idle with A/C on ended up being engine mounts as well.

Hopefully not, the right one is new and the left one checks out ok.

Mounts wouldn't account for the varied Injector values???

Checked the Web and it says the way to check the AC clutch coil is by checking ohms across the coil, should be between 3 to 5 ohms.

Checking mine shows 4.0 ohms so I hope it means it's all good. So that counts out the AC clutch coil.

Then seizing compressor.
Excessive refrigerant head pressure.