RFI Interference from Fridge/Freezer

[pathfinder]

Hi Guys,
I'm not a Refrigeration Engineer, but a self-employed TV Engineer who has become involved with this problem...
For the last month or so, every hour or so I got a 3 to 5 second burst of Radio Frequency Interference that totally breaks up TV pictures or obliterates any Radio Reception.
I was completely puzzled as to the source of this until one day I happened to be sitting in the kitchen listening to the radio, when the burst started.
I heard a pronouced "click" come from the Fridge/Freezer, just at the exact moment the interference stopped.
I have a quite old 2 Cabinet (stacked) unit which I presume uses a dual compressor.
I've tried shutting down the compressor via manually adjusting the Defrost Timer, but that's clean, both in starting and stopping.
The door switch is also not to blame.

Today, since the fridge was almost empty, I left the door open until the fan started...again "clean".
I then closed the door.
After about 10 mins or so, the blast of interference could be heard on the radio, just at the point the fan shut off.

Do you guys reckon this could be caused by the fridge thermostat arcing?
(There is obviously arcing going on somewhere!)

I'm not being a cheapskate here in not calling out an Engineer, firstly, since the unit is pretty old now and would not warrant the charge of a professional Engineer.
Also, being an Engineer myself, I tend to get involved LOL!
And last (but not least)...I don't earn a lot of dough, so it would be good for me (and the environment) if I could squeeze a couple of more years out of it.

It's bugging me!

So should I try a new thermostat, or could there be other factors?
The fan motor I would imagine would be a brushless/induction type..so I would tend to rule that out.

Would very much appreciate any thoughts on this....


PF.

[Brian_UK]

Hi Pathfinder, welcome.

Having read through your post a couple of times I tend to agree with your analysis and would suggest changing the thermostat.

It is possible that over the years the contact points have developed some pimples and the changeover spring has weakened. When you consider the cost of a new 'stat compared with a new unit it has to be worth a try anyway.

You should (he says confidently) be able to get a new 'stat from your local domestic supplier or repair shop; just be very careful when changing it - do not puncture any tubes !!

Good luck with it..

[chillin out]

hi pathfinder

can`t you rob some bits out your tv s to make some sort of choke supressor type thingy this must be cheaper than a new stat wich might not even sort it out

[chillyhamster]

Years ago in the good old days of Thorn EMI, who made Tricity refrigerators. They had a surge suppressor for exactly this problem. Even new thermostats can arc when breaking the circuit, it all depends on the rate of change in the phial temprature and the spring tension of the fast make / break arrangement.

[chemi-cool]

Don't rule out the starting relay at the compressor contacts.

It might have bad contact just as well.

Dust that enter into those control part, usually causes the problem.

pathfinder, When you got it solved, please share with us you success.

Chemi

[pathfinder]

Thanks for considering my problem, chaps.
So, have I got this right....?

When the Fridge thermostat cuts in, it switches on the (Fridge)compressor via a relay (in the compressor housing) and also the Fridge fan at the same time?

I considered going down the "suppression" road, but I felt that this would be curing the symptom rather than the fault, which is just going to get worse until complete failure.

The worst thing about working on Fridge/Freezer equipment is that you've only got a short window of "down time" if you have nowhere to store your frozen stuff.
So you've really got to plan ahead exactly what work you are going to do, with no time for pondering or fiddling about! LOL!

I'm sure you guy's know all about that already though.

I'm going to proceed carefully and really just make observations in the meantime rather than just diving in.

For instance, I thought the thermostat switched the compressor directly and not via a relay.

So if anyone has any other views or suggestions (other than "Call an Engineer"), then I would be most grateful.

cheers

PF.

[chemi-cool]

You did not state the manufacture name and model so it is not clear which fan you refer to.

Some models, have a condenser fan, located under the unit next to the compressor and runs with it.

An evaporator fan will be found in the freezer behind the back wall running at all time except on defrost and when coil temp is under freezing temp. It is controlled by a small defrost thermostat located on the evaporator coil.

The relay at the compressor terminal works only on start and energise the start winding which dis connect once the motor has reached the running speed.

There should be a wiring diagram somewhere. find it and it will be clear to you.

Good luck.

Chemi