Heater Failures

I've seen a couple of modes of failure of heater elements.

Wires Coming Off

This is mainly seen in GHD3 only. The problem is that the wires come detached from the heater element. Initially this will manifest itself as the LED only coming on when the GHD's are closed. Gradually they will work less and less until the light doesn't come on at all. A number of people have tried to repair the heater by reattaching the wire, however I've not heard of anyone who has successfully made it reliable again. Therefore I recommend replacing the heater element with a new one (see below for heater purchasing information).

Heaters Cracked

The heaters are quite brittle and therefore can break under an impact. Therefore if you drop them, they could get broken! Mk3 GHD's won't turn the LED on if one or both the heaters are broken. Mk4 GHD's will turn on and beep as normal, however one or both of the plates won't warm up.

This behaviour can cause a secondary problem in Mk4s. If the heater that the thermistor is mounted on is broken, then the other plate will warm up, however the electronics won't know (as the thermistor will remain cold). This will cause the working plate to get hotter and hotter until the thermal fuse trips. Then you'll have a heater element and a thermal fuse to repair!

The heaters in fake GHD's seem to be particularly liable to break. If you purchased your Mk4 GHDs from Ebay and they broke within a few weeks, then they are probably fakes (sorry :-( )

Testing Heaters

If you are testing GHD3's for the heater wires coming off, just try gently pulling on the wires between the heaters and the PCB. Any bad wires will just come off in your hand.

In both Mk3 and Mk4 GHDs the heaters are in parallel when connected to the PCB. This means that if both heaters are working, then you will measure half the heater resistance when they are connected to the PCB. If you are unsure, just disconnect the heaters and then measure them on their own. If you need a soldering iron to disconnect the heaters, then you've got fake GHDs.

Mk3 GHDs have 160 ohm heaters (so you'll measure about 80 ohms when they are both connected to the PCB).

Mk4 GHDs have 70 ohm heaters (so you'll measure about 35 ohms when they are both connected to the PCB).

Replacing Heaters

Instructions for replacing a heater in a pair of 3.1b's are here. These instructions are also basically correct for GHD3's and Mk4 GHDs. When fitting heater elements we recommend applying a small amount of thermal paste. For more info about this paste, see the thermal paste page

The heaters in Mk3 GHDs are different to the heaters in Mk4 GHDs. Therefore make sure you get the right ones for your GHD version.

We stock the following two types of heater suitable for Mk3 GHDs:

The GHD MS uses a narrower element to normal. This is available here:

New 170 Ohm Narrow element

Meanwhile for Mk4 GHDs you need a 70 Ohm heater:

Resistance values are nominals - a heater will never have the exact resistance specified!

This page was last updated at 9:47pm on 9th March 2010