Electical surge question

[4xquadrod]

I am wondering why at idle, you can hear what seems like the air conditioning pump cycle even when it is turned off. I was waiting for my breakfast house to open reading the paper with the engine running and the interior lights were fluctuating. The dimming was coinciding with what sounds like the compressor cycling.

Or is this the alternator working?

 

[David Muench]

If it's cold out and the engine is cold, that's the intake grid heater cycling (the modern equivilant of glow plugs). It's a very high amp draw on the electrical system and is perfectly normal.

 

[4xquadrod]

Ah, that will work for me.



Thanks

 

[Rosco]

4Xquadrod, when you say you had the a/c off does that also mean you have the defroster turned off to. If you don't the a/c compressor will cycle with the defrosters to remove moisture in the cab. Now, if you have all HVAC controls off you may be hearing the "NEW" for 03' electric fan clutch engaging.

 

[David Muench]

That's true, but I don't think the A/C or fan clutch engaging would result in the lights dimming. That's definitely the grid heater.

 

[Rosco]

David is right, when I answered I forgot you said the lights were dimming also. You are probably hearing a relay clicking the heater grid on as Dave stated.