air con comp exciter coil works how?

steptoe · Post by **steptoe** » Wed Feb 04, 2009 12:57 pm

just curious about the exciter coil (think term is correct) on the front of air con compressor units of L series anyway,. Has two wires so it is just an on off thing. Is it there to ensure comp is turning before anything else happens within the air con?

I have found it contains a magnet in the centre on the side facing compressor and think it must work with those three fingers ruuning on front compressor wheel SO... it is not like a cruise control magnetic pick-up coil because thet don't contain the magnet (magnet goes on tailshaft or driveshaft and coil is fixed to body)

How do you pick up a signal from these coils ? Is it a duty cycle function of a good multi meter ?

BaronVonChickenPants · Post by **BaronVonChickenPants** » Wed Feb 04, 2009 2:25 pm

If your talking about what I think your talking about it is essentially and electromagnetic clutch.

When power is applied to those 2 wires it engages the compressor with the drive pulley, without power the pulley is just a glorified tensioner and provides (almost) no resistance.

Jordan.

Gannon · Post by **Gannon** » Wed Feb 04, 2009 4:29 pm

Jono is referring to the revolution sensor on the front of the compressor.

It is either one of 2 things...

A simple coil who's inductance changes whenever one of the 3 prongs passes it. The AC amplifier could read this sensor by feeding a certain frequency to the sensor and sensing changes in impedance.

A 'Hall effect sensor' which is a semiconductor who's resistance changes when the sensor is brought close to a metal object

BaronVonChickenPants · Post by **BaronVonChickenPants** » Wed Feb 04, 2009 4:45 pm

Aah right, I'm used to the simpler world of MY gadgetry, on or off, none of this fancy pants sensing hoohar

Jordan.

steptoe · Post by **steptoe** » Wed Feb 04, 2009 9:12 pm

ah yeh, off course , I have only just learnt what others have simply called an air con relay up behind the glovebox is called an amplifier.

was wondering if this beast could be used for other purposes in a different spot such as rev pulse generator, but thinking not, it is whatever causes the clutch on air comp to engage ain't it ?

Hey Jordan, good to see you still looking in here at times.

YouTube · Post by **El_Freddo** » Sun Feb 08, 2009 7:30 pm

BaronVonChickenPants wrote:Aah right, I'm used to the simpler world of MY gadgetry, on or off, none of this fancy pants sensing hoohar

Me too - my '88 L is the same, yet every other model of L (my sister's '84 and the 'spare' 94 that we have) i've seen has the same said black box and three prongs on the front of the AC compressor pulley. And the system doesn't work if that box is not connected at the plug - I found this out the sweaty way the other day...

Cheers

Bennie