How to Convert Excalibur to Low Heat

Excalibur is notorious for its inaccurate temperature control, as discussed here under Excalibur Tech Specs. Users have found they’re cooking their food!

First, determine you have a problem. Use a Digital Thermometer to measure the temperature inside the dehydrator over a few hours.

If the thermometer shows that your Excalibur is heating up or cooling down — the actual temperature inside your dehydrator fluctuates higher or lower than the temperature you set on the dial — then here’s how to remove its cheap thermodisc and insert an accurate thermostat in its place.

Thank you to Rhio, author of the bestseller rawfood recipe book Hooked on Raw (#ad) (at for leading me to Patrick Collins, musician at, who in turn gave me these instructions.

BIG Thank you to Patrick for the text and diagrams below. I hope all the rawfood world buys your new CD as an expression of our thanks… 🙂

This is an easy job for someone who knows electricity and wiring. DO NOT do this switch in the first year because you will void the Excalibur warranty.

Please only do this conversion if you are thoroughly knowledgeable and competent in the field of electronics. This website and its owner/author are not responsible for any damage that may result.

Please do not email any questions on this. All I know is the info Patrick gave me below.

Parts Needed

To successfully convert your Excalibur Dehydrator to a low heat unit, you will need the following parts, e.g. from Radio Shack:

  • one standard 5-20 amp 2-position ON/OFF switch,
  • one fuse holder containing a fuse — 5 amps for 9-tray model, 3.5 or 4 amps for 5-tray,
  • packet of wire ties, at most electronic stores.

Step 1

Remove the back panel of Excalibur dehydrator and remove protective metal screen. Disconnect all wires and plugs.

Remove the Therm-o-disc controller (throw away) and replace with a standard 2-position on/off switch. The hole in the metal shielding (previously occupied by the therm-o-disc) is not big enough for a switch to fit. Use a power drill to widen the hole in the shielding so that you can mount the switch.

Step 2

Remove the power AC cord and replace with a 3-prong grounded power plug.

There is a clip which locks the original power cord into place. Remove this clip as it will interfere with the wires running to the Ranco unit. Make sure the new 3-prong power cord has the three wires white (+), black (-), and green (ground) exposed.

Step 3

Use a soldering iron to rewire the circuit to the following specifications:

  • AC “+” goes to on/off switch terminal 1
  • AC “-” goes to neutral “-” of fan
  • GROUND goes to the metal shielding case
  • ON/OFF switch terminal 2 goes to input of fuse holder
  • OUTPUT of fuse holder goes to “+” of FAN
  • OUTPUT of fuse holder ALSO goes to “120” terminal on Ranco unit
  • COM terminal on Ranco unit goes to “-” of AC
  • “120” terminal of Ranco goes to “C” terminal of Ranco
  • “NO” terminal of Ranco goes to heating coil terminal #2 (this is the middle one, terminal 1 and 2 are connected by a thermal fuse)
  • Heating coil terminal #3 goes to “-” of AC

So, AC+ (hot/white) is going through the switch, through the fuse, into the fan “+”, to the 120, the “No”, and the “C” of the Ranco, and to terminal #2 of the heating coil.

AC- (neutral/black) is going to the “-” of the fan, the “com” of the Ranco, and to terminal #3 of the heating coil.

GROUND (green) is going to the case.

NOTE — Make sure that all wires running to the Ranco unit are exiting the dehydrator through the same hole which the power cord is run through.

Use heat shrink to cover all the exposed soldered wires.

Step 4

Re-attach and screw on metal protective screen over fan and heating coil.

Run Ranco unit’s temperature sensitive wire (thick wire with heavy plastic black tip) through the hole containing all the other wires. Run this wire up towards the top (keep away from the fan and heating element) and mount to inner part of the protective screen. Use wire tie to tie the thermal detector to the actual screen.

Step 5

Using wire ties, wrap all loose wires together into single bunches, and position them away from the fan and heater.

Make sure any part of wires which could potentially touch somewhere on the circuit (such as the casing or another wire) is not exposed (use heat shrink, or some other method).

Rejoice, for you have a low heat Excalibur Dehydrator!

Wiring Diagrams

re-wire 9-tray
Diagram to re-wire 9-tray Excalibur
rewire 5-tray
Diagram to re-wire 5-tray Excalibur

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