Thermal Fuse Replacement

This problem occurs all the time on GHD 3.1B and SS2s. The problem is solved in the Mk4's as they use a high rated thermal fuse. Therefore if a mk4 fuse fails, there is some other fault that caused it such as a broken heater element or a thermistor problem. The thermal fuse on GHD3 models is nowhere near the heater plates so never fails (even in fault situations!)

Note that a thermal fuse is not the same as the 3A fuse found in the plug - this is a totally different problem.

If you need to buy a thermal fuse, then see the page about purchasing a thermal fuse

The Cause of the Problem

GHD used a thermal fuse that is rated to trip at 216 degrees celcius (part number SF214K). This might seem fine, as the temperature doesn't normally go above 200 degrees celcius, however this fuse suffers from "pellet shrinkage" more than the higher rated version during extended exposure to high temperatures. This means that gradually the internals of the fuse shrink and once they've shrunk below a threshold, the fuse fails prematurely. This causes the straighteners will completely die - no light, no heat, nothing.

Note however that thermal fuses can trip (like they are supposed to!) due to failures on the PCB (for example the triac going short) so always take care to check the operation of the GHD's after replacing the fuse.

For the particulary interested people reading this, then check out the "Thermal pellet Size (After High Temperature Holding)" section on page 13 & 14 of this technical datasheet and compare the SF214E and SF226E graphs - that should explain why the SF226E is better!

Testing the thermal fuse

The thermal fuse is the two brown wires coming out of the ceramic plate assembly on the switch side arm of the GHD's. If you put a multimeter across those two terminals (with them disconnected from the mains!), then it should be be close to zero ohms (maybe 1 ohm at worst). This means that when testing the thermal fuse you should see a similar output on your multimeter display as if you touched your meter's probes directly together. Don't get caught out by "OL" which means the thermal fuse is open circuit. If you've got an intermittent pair of GHD's, then you may want to try pulling / pushing on the wires slightly whilst measuring the resistance to see if it's the thermal fuse that is causing this.

The Repair

Please Note: By no means am I saying that the following repair method is safe and reliable. All I'm telling you is how I've done it. Before you perform this repair I suggest you consider the risks of this repair for yourself and only proceed when you are happy. Just cause the internet told you, doesn't mean it's right ;-)

The thermal fuse GHD use is an off-the-shelf component potted in a ceramic pot:

I've heard some people have dug the old fuse out of this pot using a scriber or point of a dart and potted a new one in it's place. This is a very time consuming process and is easy to get wrong (i.e. break the pot by a mistake whilst digging the old component out). If you decide to use this methog, then make sure the potting compound you use can not only stand the temperatures, but is also thermally conductive so the fuse would trip in the event of a failure!

My prefered solution is to take the wires off the old thermal fuse and crimp them onto a new thermal fuse using bootlace ferrules. I then carefully wrap the entire thing in a number of layers of Kapton Tape to electrically insolate it from the heater plates.

The thermal fuse I use when I do the repair is rated at 227 degC. Here are some suitable parts from a number of suppliers:

Here is what my replacement thermal fuse looks like. The top one is the original fuse (with the wires cut off ready to be transferred to the new fuse) and the bottom one is my replacement.

If you don't fancy making your own replacement thermal fuse, then see the page about purchasing a thermal fuse

How to replace the thermal fuse in GHD 3.1

Photographic guide is here.

Frequently Asked Questions

Can I simply bypass the thermal fuse?
It would work fine, however if you leave the straighteners on by a mistake, or if they go wrong, there is no safety cut out and could cause a fire.
How do I get the plastic cover off the heater plate?
It's difficult and the best way I have found is to slide it off the end of the heater. If you try to "flex" it off, the clips will break. See this guide for more info.
Are there any dangers in doing this repair?
The thermal fuse has mains voltages going through it. Therefore whatever method you use, you need to make sure it is electrically isolated from the metal clip that holds it in place. Note the standard GHD thermal fuses come with a layer of Kapton tape just to make sure the thermal fuse does not touch the metal clip!
Where can I buy a new thermal fuse from?
See the page about purchasing a thermal fuse
What is / where can I buy Kapton Tape?
See the page about Kapton Tape

This page was last updated at 2:17pm on 18th June 2011