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Help Replace Discontinued Range Hood Vent Fan Switch Answered

The variable speed fan control on my Thermador HT48HQS hood vent does not work and the replacement switch is no longer available.  I'm looking for some help in making a new switch.  The Thermador VTR1000Q motor is mounted on the roof and controlled at the hood with a variable speed control knob. The motor is rated at 115V 60Mz 7.8 Amps. Photos of the switch assembly are attached.

From what I understand, the speed control knob is a potentiometer that regulates the speed by proving a range of amps from 2.5 to 8?

If I could make a variable speed control that would be great.  But I'd be more than happy to have create an on/off toggle switch or a toggle for low on/off high.  Can anyone help me?

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jordevo42

6 months ago

Alright folks. Ive been chasing after this EXACT issue for a few weeks now. I found some parts, by running model numbers and found that if you buy the part IN the black plastic casing, it will cost you around $80. Thats unacceptable. Opened the first box up and found the potentiometer. Spent a great deal of time cross referencing and chatting with CTS and finally was able to order the click spin control knob for like $5. the part is 450T328F102A1C1 from CTS Potentiometers, and the best place to order it through is Mouser electronics.

I got that sucker in the mail, soldered it up and whamo, nothing at all. So I went to the second box, (CM-18RSTU2) which is the circuit board. That is where the problem lies, in the same resister that was previously shown.
I have had no luck thusfar in finding that circuit board. I gather that the reason the parts are so hard to find is because they change slightly in design and its hard to follow. It looks like this circuit board would typically house the potentiometer in the cut out circle.

Some one mentioned simply replacing the resistor that is toast using a 1w vs a 0.5w. Is that a somewhat accurate guess as to what the wattage was in that resistor? I want to try that first, but have no clue as to what value that resistor ever was before it burnt up.

We will solve this.

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bobvu2018

1 year ago

This thread was along time ago and I just run into the same issue so I wonder if you were able to resolve it?

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Cjmacyogiboobobvu2018

Reply 10 months ago

Nope. I’ve been cooking without a hood vent for two years (seriously). What did you do about yours?

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Downunder35m

2 years ago

I have seen a lot of shortcuts taken when it comes to saving a few cents on making a product - this must be within the top ten!
Finding a genuine replacement seems to depend on the part of the world you call home and how good you can talk to my friend Google, I found this for example.
As there is nothing in your box the only thing that could have failed is the potentiometer - did you measure it?

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CjmacyogibooDownunder35m

Reply 2 years ago

Unfortunately, the link you sent is for my part, but it is discontinued and unavailable (as it is for every appliance part site i've searched). My electrical IQ is pretty low, and I haven't figured out how to test the potentionmeter with my low-end multimeter. I know the switch is bad because I could smell it burning when it stopped working. You can see the scorch marks on the board of the second part wired to the potentiometer (the insulation on the blue wire even melted a bit). So I'm still wondering if there is a way I can wire the fan with a simple on/off toggle switch so that it runs at full power when on.

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Downunder35mCjmacyogiboo

Reply 2 years ago

Sorry I missed this burnt bit before.
In that case it should be cheap and simple.
Only problem is finding the correct value for the burnt resistor.
If there is enough room inside I would go for a slightly more powerful version, for example 1W instead of 0.5W.
That is assuming the potentiometer itself is still fine.
Grab a few different resistors values and check what happens.
Start with the same value as the working one and if no luck or wrong speeds try other values.