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Tuttnauer 2540M Autoclave Repair – No Heat & No Heat Light – Here’s How To Find & Fix The Problem

Tuttnauer 2540M Autoclave Repair – No Heat & The Heat Light Doesn’t Come On

The other day I got a call from a client stating his Tuttnauer 2540M Autoclave Wasn’t Heating.

He said the power light comes on and when he turns the Dial to EXH/Dry (Vent/Drying Cycle), the Dry Light Comes On, But the Heat Light Never Comes On, and The Chamber Stays Cold.

So, what’s the problem?

The symptoms (the lights coming on while the heat light staying off) tells us there is in interruption in the electrical circuit somewhere between the power coming in and the heating elements. Meaning there was a break in the line somewhere stopping the power

Tracing The Problem With The Tuttnauer 2540M Autoclave Using The Wiring Diagram

By looking at the Tuttnauer 2540M autoclave wiring diagram below, you can see since the power and dry lights are coming on, you can quickly eliminate all of the other parts in between.

Tuttnauer Manual Autoclave Wiring Diagram

Click On Diagram For Larger Picture You Can Print

So now we know these parts are good and not causing the problem: The Circuit Breaker, the Manual Safety Thermostat, The Power Switch, The Power Lamp, The Timer, The Automatic Safety Thermostat, The Micro Switches MSW1 & MSW3. And that leaves only the Temperature Controller, The Door Switch, The Heating Elements and the Micro Switch MSW2 left in the circuit.

We also know the Dry Light is coming on when you turn it to the EXH/DRY cycle. This light is activated by the Micro Switch MSW2, so we know that switch is good as well and can eliminate it from the possible suspects. Knowing the Heat Lamp is not coming on and the chamber is cold, tells us the break in the line is happening before it gets to the heating elements, so we can rule them out as well.

Now we are down to just the Temperature Controller & the Door Switch and both of these parts will need to be tested to find out which one is defective and causing the problem. At this point, the first thing you want to check is the wires running between these components to make sure you do not have any loose, broken or burnt wires

Time To Test The Two Remaining Components On The Tuttnauer 2540M Autoclave

It’s now time to drag out your ohm meter if you don’t already have it out. And we will be using the simplest and easiest test there is in electronics: the “Continuity Test.”

If you don’t already know what continuity is, think of continuity this way: You have a piece of wire. The wire is intact with no breaks in it. It is said to be continuous.

If you were to place a probe from your meter on each end of the wire at the same time, (while the meter is on the setting for continuity) your meter would show it to be continuous.

While your probes are still touching the end of each wire, if you were to cut the wire, then there would be a break in it and it would no longer be continuous.

Okay, now let’s get started with our tests, starting with the temperature controller (make sure the autoclave is unplugged from the wall before performing these tests)

Thinking it through:

The temperature controller simply allows power to pass through and onto the heating elements until it reaches the preset temperature. It then cuts the power until the temperature drops to a certain point and the power is restored. It continues this pattern until the cycle is completed.

So turn the temperature up and test the leads on the controller terminals (touch the terminals with the probes…not the wires)

If your meter shows continuity, then it is good and not the problem. If not, replace the temperature controller. Click Here To View The Tuttnauer 2540M Temperature Controller

Now, assuming the Temperature Controller tests out good, let’s move onto the Door Switch.

The Door Switch on the Tuttnauer 2540M Autoclave is a safety device. It keeps the heat from coming on by not allowing the electricity to pass through to the heating elements until after you close the door

To find the Door Switch, simply open the door and look for the button coming through the face plate of the autoclave towards the top on the end where the closing device is located

So, when the door is closed it pushes the button on the switch in.

A couple of electrical terms it will help to know: “Normally Open” & “Normally Closed”

The state of the Switch is considered as Normally Open. That means it is not continuous (like a broken piece of wire). Power cannot pass through it and onto the heating elements. With the Door open, the switch is Open as well.

When the button is pushed in, it completes the connection inside the Door switch and allows the power to pass through, making it continuous. Door Closed, Switch closed

The Door Switch on The Tuttnauer 2540M Autoclave has three connections (terminals) on it: COM (for Common), N.O. (for Normally Open), and N.C. (for Normally Closed). The Tuttnauer 2540M Autoclave Door Switch only uses two of these. The COM and the N.O.

Again, with the autoclave unplugged, the door open, and your meter set on continuity, place a probe on the COMM terminal & the N.O. Terminal (where the wires are)

If your meter tells you it is Closed (continuous), then the switch is bad and needs to be replaced.

Now close the door and put your probes back in the same spots. Your meter should now read continuous, if not, it is defective and needs to be replaced

In this case, it was the door switch. You Can Find The Tuttnauer 2540M Autoclave Door Switch By Clicking Here

Replacing the Tuttnauer 2540M Autoclave Door Switch is fast & easy, with no special tools required……and the switch is inexpensive!

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2 Responses to “Tuttnauer 2540M Autoclave Repair – No Heat & No Heat Light – Here’s How To Find & Fix The Problem”

  1. patti says:

    tuttauner2340m heat light will not come on chamber stays cold …when put in exhaust vent cycle heat light come on..tried new thermostat but no luck..any suggestions.>

  2. Wally Wally says:

    Good Morning Patti

    Your unit has 4 heating elements on it. The two located on the rear of the chamber are the ones that should be coming on during the heat up/sterilization cycle…and it sounds as though they are not.

    The other 2 heating elements come on during the drying cycle. They are working and that is why the heat light is on after venting

    Testing the heating elements is a fairly simple process. You can go to our website for the instructions by clicking here and scrolling down the page


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