Jacobs refridgeration

[r500]

  Sounds like the contact point in the thermostat is welded shut. Replace the t-stat.  Have your a/c guy come back and and check that the charge is right,  have him raise the head pressure to 30 deg. above ambent temperature and monitor box temp. when it reaches set point make sure head presure is at 30deg. above ambent temperture and the charge should ok.  These boxes have a cap tube and are critically charged systems.

[davethebirdman]

Thanks for your advice... The T Stat I ordered from Funtroincs arrived today... I have fitted it and its still got the same fault..

Its running and getting cold but If I turn the T Stat off the compressor just contiunes to run...

I'm at a bit of a loss....

Th is old girl is almost four years into her restoration and I thought I had it solved with the new T Stat...

Dave

[johnieG]

Again, sounds like your compressors getting some back-feed voltage from somewhere,

so say if you'd open/disconnect the wires & insulate them (temporarily with electrical tape)from the back of the thermostat. I assume the compressor will still be running?

I know some older machines have a large start/run relay assembly that's housed in a large tin box, and the start/run relay in this type of setup is controlled by the thermostat, but the compressor doesn't get any direct line voltage delivered to it from the thermostat itself, 

if this is the case you may have a pair of spot-welded contact points in the start-run relay itself which wouldn't allow it to shut off no matter what the thermostats set at.

[davethebirdman]

Hi Johnie...

The compressor doews have a large tin box with the start-run realy in it you're right...

I haven't actually put the two wires together to see if it will just continue to run but I'm gueesing that it will..

Its night time here now.. Will try the two wires togther tomorrow...

Is it possible to by pass the compressor start- run with a 3 in 1...?

Dave

[johnieG]

Dave...I meant that you should remove the wires from the thermostats' terminals & tape them up (so they don't short out or shock you) & see if the compressor still runs continuously, 

Yes it's possible to use a 3-in-1 in place of the original start/run relay, does your compressor have three external binding posts/terminals ( three in a row, as opposed to a modern compressors three in a triangular pattern)?   

[davethebirdman]

Hi Johnie

this is a picture of the terminal block on the compressor...

What do you reckon??

Dave

[johnieG]

Is the wiring as shown original?

OK, Good...the terminal with the copper strap is definitely the "common" connection, ( sometimes marked/stamped on the metal case as "C" for "common")

the Red wire should be "Run" ( sometimes marked/stamped on the metal case as "M" for "main")

the white wire should be "start"  ( sometimes marked/stamped on the metal case as "S" for "start")

The better way to check is to remove all the wires from the terminals, & use an OHM meter to measure the Resistance readings between the COMMON terminal & the other two, the HIGHER reading is the start terminal, the LOWER reading is the run terminal.