resistor burning out please help. suggestions input needed.

Thread Starter

dwoodby

Joined Jun 21, 2021
5
Jey just signed up on here and wondering if anyone might have some insight. So this PCB is out of a mini split air conditioner and the circuit board lasts until outdoor temps get to about 90 degrees. this same resistor always burns out and the board is about 300 to replace. Does anyone have any suggestions for first off just what do i need to just replace this as is. and 2 is there a way to upgrade this to something better and it still work.,
 

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ErnieM

Joined Apr 24, 2011
8,196
Looks like a 20 mili ohm (0.02) 5 watt resistor from what I see. 5 watts should be good for 15 amps.

Is there any room to add even a small fan over that board?
 

Thread Starter

dwoodby

Joined Jun 21, 2021
5
no room to add a small fan. would it be feasible to go up on the watt rating of the resister. maybe another type of resister?
 

LowQCab

Joined Nov 6, 2012
1,307
It's very faded, but it's clear enough to read ......
It's 20-mOhms, or, 0.020-Ohms.
I wonder what they are using that Value for ???
Maybe a Current-Shunt to measure Motor Current ??

This needs to be replaced by a proper "Chassis-Mount" 10-Watt Resistor,
that has some steady Air-Flow over it,
this will also take some of the Heat-Load off of the rest of the components on that Board.

What this Board really needs is a dedicated Cooing-Fan.

Here is a replacement Resistor ........
https://www.digikey.com/en/products/detail/te-connectivity-passive-product/HSA25R02J/2731190

Be sure to use 16-gauge, Fine-Stranded, wire,
and keep it as short as practical,
Try for no more than a total of 12" of Wire,
this is an extremely low value Resistor, and excessive Wire length can actually
change the total Resistance, ( Wire-Resistance + Resistor-Value ).

Here's an alternative solution ..........
Go to a Hardware Store or Walmart and purchase
a cheap, 16-gauge, Triple-Tap Extension-Cord.
Read the packaging carefully to make sure it uses 16-gauge "Zip-Cord" Wire,
almost all of them are 16-gauge.

Cut of the Plug,
Cut a section of Zip-Cord exactly 32-inches-long.

16-gauge Wire is 0.004-Ohms per foot,
so, a section of 16-gauge-Zip-Cord, 2.5-feet long, ( 30" + 30"),
has a Resistance of 0.020-Ohms,
exactly the value of the Resistor you need to replace.

The extra 2-inches is to provide room to strip the ends of the Wires.

One end of the Zip-Cord must be Soldered together, and then well insulated with
a piece of "Shrink-Tubing", this insulated splice must be able to withstand weather and abrasion.

Route your new "Zip-Cord-Resistor" so that it will not be damaged by vibration,
use "LOOSE" Zip-Ties to secure it in a way that allows it to get constant Air-Flow so
that the insulation is not damaged by excessive Heat-Build-up.

Done ........
.
.
.
 
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