Cutting out at idle - High Elec. load

[alastairb]

Hello,

I've had this happen about 5 times now and always at idle after a drive, with stereo & air-con on - Im pretty sure its when the fans kick in so it seems to me like a spike in the electric load on the car is causing it to cut out.
After I move it to P and recycle the key off/on it starts normally.

I've got a recent-ish battery, recent-ish refurb alternator so im wandering if it could be earth cables or the fans themselves ? Are the earth straps fairly common to need a look at?
Is there a voltage cut-off on the ECU that would cause it to shutdown at all?


Out of interest I grabbed a screen grab of the voltage measured at the battery , the dips occur when the fans kick in.
Idle voltage hovers around 13.7 volts

As ever, grateful for any wisdom from the experienced minds on here.

 

[CatmanV2]

I can't imagine that a drop that small is causing the idle to die on its own. Do the fans spin freely?

C

 

[alastairb]

Yeah I guess I thought it might be useful to post the voltage chart if it rules things out.

Havent checked fans yet, certainly no odd noises - Will check them next I think.

 

[CatmanV2]

You sure it's the fans and not the compressor? The fans are electrically driven, so logically can't put a physical drag on the engine other than that engendered by the alternator working harder.

The compressor, OTOH is physically driven by the engine via a belt. I wonder if that's enough drag to stall it out. Simple test would be to stick in ECON for a while and see if it still does it. Might want to check the nose of the compressor as well. I think it gets wobbly as they fail?

C

 

[spkennyuk]

The spike when the fan comes on looks normal. Any electrical device being turned on you will see a small dip in voltage and then a recovery. Have the lights or stereo off when you start the car for example and then turn them on once running to see the slight dip.

The chart would be handy if you could catch it in the act of cutting out. If the voltage suddenly drops to zero then there is a loose connection somewhere to the battery or battery circuit.

I would check both battery terminals are both still tight along with anything connected to the terminals.

After that see if any codes are present as any undervoltage errors will be stored. If you have recently changed the battery there will be some codes present if they were not cleared when you changed the battery so clear those first and see what happens code wise if it cuts out again.

 

[Sam McGoo]

As above, I'd be checking battery terminals for tightness along with all the connections onto the +ve terminal plate before going any deeper.