Harman Pressure Sensor Vacuum Switch, 3-20-6866

SKU 3-20-6866
MPN 3-20-6866
  • Genuine Harman Vacuum Switch
  • Made in the USA
  • Ships FREE with orders over $99
  • 30-Day hassle free return policy
  • Express Shipping available
  • 90 Day Warranty On All Items
  • Learn More...


Harman Differential (Vacuum/Pressure) Switch, 3-20-6866

The Differential switch is one of the safeties that Pellet stove companies install into their stoves. If the stove is not reaching the correct pressure it could point to an issue that needs to be addressed before the stove can function safely. The differential switch will not allow the stove to feed pellets if there is a blockage or air leak. After you have made sure that the stove and venting are cleaned, all door gaskets are in good condition and doors and hopper lid closed securely try starting the stove again. If it doesn't feed it may be that the pressure switch needs to be replaced.

Replacement For Part Number :
  • 3-20-6866

Compatible Models


  • Absolute 43
  • Absolute 63
  • Accentra 52i
  • Accentra 52i TC
  • Accentra Cast Free Standing
  • Accentra Insert
  • Advance
  • Allure 50
  • HF60
  • Invincible Insert
  • Invincible RS
  • Invincible T
  • P35i
  • P35i-C
  • P38
  • P38+
  • P43
  • P43-C
  • P61
  • P61-C
  • P61A
  • P68
  • PB105
  • PC45
  • PF100
  • Pellet Pro II
  • XXV

Technical Specs

.10 WC PF


Unfortunately, sometimes products do not work like they are supposed to. We offer a 90 day warranty on manufacturer defects. Some manufacturers make this a very simple and easy process unfortunately others do not. Items must be used in accordance with the manufacturers guidelines to qualify for warranty replacement. Please be advised that warranty claims for these parts may take up to 4 weeks for processing, and customers must cover shipping.

Shipping Info

This Item Qualifies For Free Shipping With Orders Over $99!

When Will My Order Ship

All orders are typically processed within 24 hours of receiving payment and are shipped from us same day if placed before our shipping cutoff time (Monday - Friday: 1PM, Saturday: 10AM, Sunday: No Shipping), orders placed after our cutoff time are shipped the next morning.

How Does Free Shipping Work?

Most orders over $99 qualify for free shipping! Orders which ship for free are shipped with either USPS or UPS based on our discretion. If you are using a PO box, free shipping orders will always go USPS.

Is Expedited Shipping Available?

We offer both overnight and two day air shipping services for all orders placed within the Continental United States. For information on shipping cut-off times, go to our shipping page.

Do You Ship To Canada?

We ship to Canada! We estimate USPS to take 4-10 days once receiving your package from us. We do not offer expedited shipping of any kind to Canada. Please allow an extra 2-5 days for all shipments to Canada. Free shipping is not available to Canada.

Do You Ship To Alaska Or Hawii?

We ship to both Alaska and Hawaii! We do not offer next day or two day shipping to Alaska or Hawaii. Free shipping is not available to Alaska or Hawaii.

Do You Ship Outside The US Or Canada?

Unfortunately, at this time we do not offer international shipping other than to Canada.

If you wish to calculate shipping for an item which does not qualify for free shipping, or if you would like the cost to expedite your order, please do the following. Add the item you want to order to your cart and click here to be taken to the cart page where you can enter your country, state / province, and zip code for an estimate.

Shipping Time Estimations

For information on shipping time estimations, see either the Shipping Information & Transit Times on the cart page, or go to our shipping page.

Read More About Our Shipping Information

Customer Reviews

Based on 3 reviews
Harman Pressure Sensor Vacuum Switch

It is hard to rate a pressure switch. It either works or it doesn't and in this case, the switch - worked perfectly. It is easier to rate customer service. I gave my experience five stars because everything - worked perfectly. The web site is easy to navigate and ordering was painless. My order arrived on time and was securely packaged. While repeating one's self in writing is discouraged I have to say that from ordering to delivery and use everything - worked perfectly.

Works great

Item arrived ahead of schedule which is a shock because it was the holiday season. It works good. Stoves back up and running.

Great service

Great service and product


Ask a Question
  • I can't control the feed. The stove runs wide open,or I have to turn it off.

    You'd want to look at testing the room sensor or ESP sensor, the vacuum switch only opens the feed circuit

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