Roll Royce Air con

[gazcull]

Hi just been checking over the aircon system on a 79 rolls, apart from being surprised by the phyical size of the compressor (and engine) have found the magnetic cluch being held off by a small black box strapped next to the compressor, it has three pins marked S B and C , a number 3V4333a3 and writting MICROTEMP 169c, What is it?? can i get another?? also a wire to it connects to the back of the compressor( aswell as the negative and +12v), any ideas??? cheers

[Brian_UK]

I think that it is a thermal cutout used to protect the compressor.

Obviously these aren't in the box but an idea of what it is...

http://www.apart4u.com/default.cfm?viewprod&id=7245

edit: May not apply to your unit but some of the big old compressors where connected via self sealing fittings. If you ever separate one make sure that they are screwed back together fully. - If not then you blow the compressor seals etc when it starts pumping against a closed discharge.

[monkey spanners]

Its a thermal fuse designed to short out and blow the ac fuse if the compressor discharge superheat gets too high if my memory is correct.
Something else i remember about these cars is to check where the fusible plug is pointing in the reciever/drier, if its been replace and not orientated correctly it could be pointing at your face as you work on the system!!!

Jon

[thermo prince]

http://www.almaproducts.com/AboutUs.html

http://www.hotrod.com/howto/7954_air_conditioning_compressor_rebuild/index.html

Hi Gazcull, old workhorse compressor around for many years. Used on shuttlebus a/c too for many years but lots of mixed opinions on it.
About 220cc displacement 6 cyl, made by ACDelco originally, called the Delco A6 then sold to Harrison and now ALMA A6.

Good news is lots of parts and info available on it but especially in USA.

As I said, it dates back to the days of R12 and probably Suniso mineral oil. If you are converting to 134a read some of the USA chat links on todays guidelines , such as oil, seals - I think automobile industry suggests PAG oil.
http://www.autoacforum.com/messageview.cfm?catid=20&threadid=8294

Our company used it on ShuttleAire minibus a/c over some years and found it survived quite well with Solest 120 POE oil.

regards
T-P

[chillin out]

I thought it was a triac??

Chillin:):)

[Karl Hofmann]

Just had a quick scan through my RR tech manual, and my money is on it being the Compressor protection unit... Which is essentially is just a fuse.. I came across a similar idea on an old XJS... I simpy rewired it with a 10 amp fuse

[chillin out]

Just had a quick scan through my RR tech manual, and my money is on it being the Compressor protection unit... Which is essentially is just a fuse.. I came across a similar idea on an old XJS... I simpy rewired it with a 10 amp fuse
So why does it have 3 connections?

Chillin:):)

[Karl Hofmann]

One wire is the live feed via a temperature switch which opens at freezing point, this passes through the fuse to the compressor.... The third wire connects to the compressor wire via a resistor and runs to the compressor overheat switch.. When the switch is tripped, a dead short is formed, thus blowing the fuse