Microwave Won’t Start But The Timer Works? 7 Common Causes

It can seem a little confusing when the timer on your microwave works fine, but the actual microwave just won’t start.

In this article, I’m going to walk you through some of the causes of this perplexing problem. In each case, I’ll offer up either a solution or a way to diagnose the problem.

The golden rule always applies though:

If you’re in any doubt about fixing the appliance yourself, always get a professional in!

With that out of the way, here are the likely causes of this perplexing problem.

#1 A Faulty Door Switch

Most modern microwaves are designed with a safety mechanism that stops them from operating if the door is open.

Even if it looks as though the door is shutting fine, it’s possible the door switch is malfunctioning. If this happens, your timer will be on, but the microwave won’t actually start cooking.

First of all, do a manual inspection of the door and see if there’s any obvious issues with closing it. If you can tell it’s clearly broken, you’re best off replacing the appliance altogether.

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#2 A Blown Fuse

It’s possible that one of the fuses in the microwave has broken, so the timer works but the microwave itself won’t start.

If you’re qualified to do so, then by all means test it with a multimeter after opening up the control panel. Again, only do this if you know what you’re doing, or get a professional in!

You may be able to replace the fuse if you’re comfortable doing so. As with all electrical jobs, only tackle what you’re qualified for.

#3 A Faulty Capacitor

If you have a defective capacitor then the microwave may not be able to generate the necessary juice for the magnetron. This is the part of your microwave that generates the heating energy.

This is one of those jobs that I really don’t recommend trying to fix yourself, even if you’re up for the challenge. Working with capacitors can be dangerous stuff, so you’ll need to get a qualified professional in for this one.

#4 A Malfunctioning Magnetron

As I’ve covered elsewhere, the magnetron is responsible for generating the microwaves that heat your food.

They don’t last forever unfortunately, and they can only spit out so much energy before giving up the ghost for good.

It is possible to replace the magnetron, but again this is a job for a qualified professional.A close up shot of an under-counter microwave

#5 A Faulty Control Board

If the control board itself is damaged, it can stop the microwave from getting the signal to start, even though the timer’s working just fine!

If everything else is working OK, but the control panel is unresponsive, they can be replaced. Either contact a professional repair service, or replace the appliance completely.

#6 A Tripped Thermal Cut-Off

Many modern microwaves have thermal cut-offs which help to prevent overheating.

Microwaves can overheat if the cooling fan stops working properly, or the vents have become blocked.

The good news is that this is one you can try and fix for yourself and the solution is simple!

First, let the microwave cool down completely. Next, unplug it from the power outlet and check the vents for any grease or debris.

If that doesn’t work, the cooling fan can be replaced but this is another job for the professionals.

#7 Electromagnetic Interference

This one’s a bit more of a long shot, but strong electromagnetic interference from nearby appliances can disrupt the normal operation of a microwave.

Move your microwave away from other appliances and check if the problem still persists.

Frequently Asked Questions

Here are some answers to commonly asked questions on this topic.

How do you know if a microwave fuse is blown?

You can determine if a microwave fuse is blown by using a multimeter to test for continuity. 

If the fuse doesn’t show continuity (a continuous flow of electricity), it’s likely blown and needs to be replaced. 

Only do this sort of thing if you’re qualified to do so!

How do I reset my microwave?

To reset your microwave, unplug it from the power source and leave it along for around 10-15 minutes. This allows the internal electronics to fully discharge and reset. 

After the time has passed, plug the microwave back in and set the clock and other settings as needed.

Wrapping Up

I know that many of these potential solutions require outside help, but this should at least help you narrow down the problem.

Remember, if in doubt, always get a qualified professional in to inspect things. Just be aware that things can get expensive once you start adding up parts and installation costs.

It may be a better idea to think about replacing your microwave altogether, especially if you’ve had it for more than five years or so.