# switching transformer hum normal?



## mstar (Dec 17, 2010)

I have an older furnance with a Honeywell RA 89a 1074 switching transformer that has a loud hum at times at other times a low hum
When I hear the loud hum the system still works and if I turn off the power switch and turn it back on , the hum changes most the time.  
It will usually get quieter.  Sometimes tapping the box will change it.

The loud hum is more frequent but not consistant. It is hard to tell if the transformer or relay is humming   

Does this loud hum  mean the unit should be replaced?  Are there any servicable parts  or do you replace the entire unit.


Thanks.


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## paul52446m (Dec 17, 2010)

We normally replace the hole control. But a person can replace just a transformer.
 All transformer will hum. A lot of times you can be 6' away and hear them. If they are in a control box they can get a vibration going which will sound loader. This does not mean that you have to replace it.  Later Paul


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## mstar (Dec 17, 2010)

Thanks. since I have two db levels of hum I would say one is abnormal.
I am assuming you are saying these can go a long time with a loud hum and still work.
Still it is annoying to hear it through the floor in the basement late at night


And why does flipping the power on and off temporarily fix the louder hum?


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## paul52446m (Dec 18, 2010)

mstar said:


> Thanks. since I have two db levels of hum I would say one is abnormal.
> I am assuming you are saying these can go a long time with a loud hum and still work.
> Still it is annoying to hear it through the floor in the basement late at night
> 
> ...



And why does flipping the power on and off temporarily fix the louder hum?
Don't know?? I could try to BS you but i won't. Later Paul


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