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February 21, 2016

Repair of a Food Saver model V845

I had a great time doing some interesting repairs at the Repair Cafe event in Campbell River yesterday. One of the most interesting and challenging repairs was that of a Food Saver plastic bag vacuum sealer, for which the heat sealing wasn’t functioning, but the vacuum function was apparently OK. In this case, the problem was not apparently common heat strip failure, but rather a failed vacuum activated switch. Here’s what I did to diagnose and repair it.

the patient

First, after some tests and removal of the back cover, resistance tests of the heater strip turned up OK, a cold resistance of about 3 ohms. However, in-situ live tests done with the unit inverted, by pressing carefully on the plastic parts of the interlocks (while carefully avoiding live 120VAC wiring!) showed no voltage being applied to the heater. The heater voltage, about 20V AC, is normally applied via a 24VDC relay. I tried bypassing that relay with a jumper, and, that caused the heater strip to heat.  However, upon taking that relay out of circuit and testing it with a DC power supply, the relay turned out to be functioning normally. After more investigation, I finally tried testing the vacuum-activated switch as shown in the pictures; heat is not normally applied unless sufficient vacuum has closed that switch. That switch turned out to be the culprit; it was stuck with the switch open. Even direct application of system vacuum to that unit from the DC motor intake was not sufficient to close the switch. Dis-assembly showed a spring inside had shifted position and been crushed against one side of the switch.   I extracted the old damaged spring, made a new one with a spring out of an old pen, re-assembled, and, voila, the vacuum sealer heater is now working fine.  Successful test with a bag showed both vacuum and heat sealing functions to be working well.

view of lower circuit board

Vacuum-activated switch is on upper left of circuit board

vacuum-activated switch

vacuum-activated switch

vacuum-activated switch, open view, replacement interior spring in

replacement interior spring in position


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  1. Thank you so much for this article. I was just about to heave mine in the trash until I saw this page. My spring wasn’t broken, but it must have had some dirt/dust inside not allowing to make a good connection. A couple of shots with the air compressor cured all. Thanks again Friend!

    Comment by Jeff — April 24, 2016 @ 7:58 pm

  2. Jeff, you’re welcome. Glad you got your sealer fixed and glad of the feedback.

    Comment by Dave — April 28, 2016 @ 3:55 pm

  3. Hi, thanks for the article. I’m hoping to install a bypass switch for that sensor so I can seal at my own will. But shorting the switch isn’t causing the unit to change cycles to the sealing mode. (I can see why later models simply have a seal button). Any ideas where to install a user switch on that board? Thank you! I’d love to not have to buy a new one for a function I can install myself.

    Comment by emms — March 26, 2019 @ 1:13 pm

  4. Thank you for sharing.

    Comment by Angelo Q — April 23, 2020 @ 9:02 pm

  5. This article is a good one to look at, but my repair skillz kind suck.

    Comment by Food Processing Repairs NZ — June 7, 2020 @ 8:44 pm

  6. Thank you for the article. I had the same problem with a non functioning pressure switch. I took mine apart and the spring was fine cleaned out the chamber and reassembled but it did not solve the problem.

    I noticed that there was a hole in the board below the switch in which you could access the spring retaining cap. I thought that was there for adjustment of the tension on the spring. I adjusted the the spring cap by a quarter turn and wella! the sealer is working correctly once again.

    I’m assuming that the spring pressure over time weakens so in my case a simple adjustment of the spring cap may have solved the problem without desoldering the switch.

    Thanks again for getting me on the right path to solve the problem.

    Comment by Joseph Mercuri — November 10, 2020 @ 7:39 am

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