# AB PF400 heatsink overtemp fault



## Cow (Jan 16, 2008)

A customer called and stated they had a "heatsink overtemp" fault on their drive that wouldn't clear. It would fault either immediately or within seconds of a run command.

I verified the fault causes and remedies in the manual. Check the fan(s), make sure the heatsink fins were clear, ambient temp, etc were all okay. Everything checked out.

It's mounted outside in an unheated/unconditioned enclosure where the ambient temp was around 20-30 degrees today. My local AB rep mentioned there was a technote about this fault coming up when the temp got too LOW as well. I found the technote on internet, sure enough, when the thermistor in the drive goes out of range, too low, it can fault the drive as overtemp.

We pointed a propane heater at the drive for an hour and a half, gently warming the drive, not trying to torch it:jester:, it still faulted immediately. I called AB tech support at this point, they had nothing worth mentioning that I could do to bypass the thermistor, just to get the drive to run. I ended up bypassing the drive completely, and now have a 125HP well pump ran straight from a breaker just so some cows can get a drink of water.

What a bummer. 

It's a shame having to replace a drive this size just because the internal temperature monitoring circuit is out of whack. These things aren't cheap, but I bet we got 8-10 years out of it.

On the bright side, a rebuilt PF400 is only a few days out. I'm so used to hearings weeks of lead time on my material orders lately, a few days out was a nice change.


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## Safari (Jul 9, 2013)

Good you Got the cows to have a drink. 125HP straight from a breaker is something I will never do.better wire in stardelta.
Had this kind of fault in our 37kw Yaskwa drive. Increased the temp setting to the maximum as per drive which was 150 degrees Celsius.Never did the problem re-occur


Sent from my HUAWEI Y330-U01 using Tapatalk


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## John Valdes (May 17, 2007)

Sensor could be bad?


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## telsa (May 22, 2015)

Cow said:


> A customer called and stated they had a "heatsink overtemp" fault on their drive that wouldn't clear. It would fault either immediately or within seconds of a run command.
> 
> I verified the fault causes and remedies in the manual. Check the fan(s), make sure the heatsink fins were clear, ambient temp, etc were all okay. Everything checked out.
> 
> ...


You want to just warm the thermistor -- with a (Milwaukee) heat gun.

You'd be surprised how quickly the high temperature of a flame tip vaults away in seriously cold weather. The hot gases just SHOOT skyward. 

Hence, the need for blown air from a heat gun. That's something that you can force into the nooks and crannies without frying the electronics.

You might think about a 'block heater' scheme for your chilly situation. Electronics just don't like to get quite that cold.
*
Differential expansion will cause connections to pop loose.*


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## JRaef (Mar 23, 2009)

If you dug down into the drive you would find the thermistor, but it would likely check out as being OK. That's because the failure is usually an A-D (Analog to Digital) converter on the control board that the thermistor is wired to. The microprocessor is looking for a specific band of digital values coming from that A-D converter. When it fails, the digital value jumps to -65,536 or 65,536, which is out of range either way and the mP interprets any value that is out of range as a trip value. But the trip message is programmed to only say "Over Temp" because that's the 99.999% cause of an out of range value.

Years ago there was a rash of A-D chip failures from several mfrs that hit everybody. Most failed within moments of being used, some lasted days, weeks, months even years. Yours lasted almost a decade. Not bad really.


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## Cow (Jan 16, 2008)

I was hoping you'd post Jraef. I knew you would know what was going on with this thing. Thanks.


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