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Hello Tony, R,
Thanks for your reply – that’s my understanding of how PTCs work too – but interestingly I’ve tested my few remaining Chinese dodgy ones that haven’t been used, plus four or five others that I’ve scavenged from old fridges that are being dumped by connecting up the OHM meter, measuring the resistance then heating them with the hair dryer to warm up the PTC while watching the resistance reading – and what I’ve found in every case is that the resistance decreases when they get warmer, so they seem to be acting like an NCT rather than a PCT. Some of them do say PTC on the casing but have this characteristic even so.
This isn’t what I expected at all :o. Might anyone know the reason?
Thanks again,
Paul QQQA second question on PTC resistors –
From my research it appears that the resistance increases as the heat rises, and the heat rises once you put a current through them on the fridge. However I’ve now tested three different PTC resistors and for each of them the resistance drops when I heated them with a hair dryer which seems to have been the opposite of what they ought to do!
Has anyone any idea why this is? According to internet articles a PTC resistor’s resistance should increase when it’s hot. My results show the opposites.
I’m confused!
Update on the above … I’ve scavenged a PTC resistor from a fly-tipped fridge and now all is working well again, so on this case it doesn’t appear to have been the compressor … although that’s what the so-called ‘engineer’ diagnosed it as.
I think it’s slightly different – if you buy replacement parts cheaply on-line from China maybe you’re getting the parts from batches that have failed the ‘manufacturer quality’ quality test i.e. the best batches go to manufacturers as it would be useless to them if the average life of their fridges was between 1.5 days and two weeks! Perhaps the batches that fail these tests are sold off individually on ebay for a few quid etc…and you’re just taking pot luck on what you get.
