# NTC Thermistor Replacement?

#### wayneh

Joined Sep 9, 2010
16,399
Here is an in-rush limiting thermistor from a motor controller, on an A/C condenser fan outdoor motor: Genteq 142R, 1/2HP, 240V.

The labelling is clear but I don't know how it relates to specifications I should be searching for. I suppose "1,0" means 1.0Ω and that the 1450 relates to the temperature factor or maybe the current rating?

BTW, it has failed to open and this is apparently a common failure mode on these. If I can replace this thermistor, and it's truly the only problem, it'll save about $1,000. Thread Starter #### wayneh Joined Sep 9, 2010 16,399 OK, I'm a little closer now. It's 1.0Ω (at 25°C) and made by EPCOS, part of TDK. 21mm. Should I care about the "1450" or just find another 21mm, 1Ω thermistor? #### andrewmm Joined Feb 25, 2011 565 look at a data sheet for the devices , they tend to have the same format, that should tell you what the 1450 means Thread Starter #### wayneh Joined Sep 9, 2010 16,399 The 1450 could be the production date. That's what I decided. I went ahead and ordered from Digi-Key Same Ohm rating, same physical size, same manufacturer. Seems likely to be OK. #### andrewmm Joined Feb 25, 2011 565 Well, not the bets of dat asheets is it. There is the line "Component marking includes the manufacturer's logo, resistance value and date code " so as you have identified the logo and resistance, the remaining , "must" be some sort of date code ! Thread Starter #### wayneh Joined Sep 9, 2010 16,399 Rats. The replacement part worked. For about 2-3 minutes. Then the fan wound down and stopped again and the compressor soon shut down due to overheat. I assume the new thermistor burned up like the last one. So I assume the ECM is bad. That's bad, because it cannot be purchased separately from the motor and together they're close to$1000 if you can find one.

A LOT of people correctly point out that the tiny efficiency gain from the variable speed motor is more than offset by the expense of replacing these silly things. Mine was only 5 years old and I gather that's typical. Compare to 30+ years for a traditional motor. You can find a handful or more of YouTube videos describing a scheme for replacing an ECM with a traditional motor plus relays to replicate speed control. I might have to resort to that.

On the upside, I think the old motor might make an awesome windmill generator.