2. Guides
3. Mk4 Debug

Repair Guide for Mk4 (Mk IV) & Mk5 GHDs

This page should help find most problems with Mk4 GHD models including 4.0B, 4.1B, 4.2B, SS4.0, 5.0 MS5, SS5 etc.

Completely dead - no light, no beep, nothing

There are a few possible causes:

• The R8 resistor (R8 or R11 on 4.2B/P and Mk5 models) has/have gone high in value or open circuit - see this page
• Still dead despite changing R8 or R11, change the PIC processor.
• The heater on the thermistor side has failed causing the thermal fuse to fail - see this page.
• The PIC processor has failed.
• The thermistor has failed.
• The thermistor has come detached from the heater element (and so is not measuring the temperature correctly) and this has caused the thermal fuse to fail - see this page.
• There is not enough thermal paste under the switch side heater element meaning it has got hotter than normal and has caused the thermal fuse to fail - see this page.
• An intermittent cable connection has caused the PIC processors memory registers to get corrupted which has caused the heater elements to get stuck on and trip the thermal fuse. The corruption in the processor will have been fixed by a power cycle. Try replacing/lubricating the cable socket and replacing the thermal fuse.
• Arcing in the power switch has caused the thermal fuse to fail. Try cleaning up the contacts in the switch (but be careful not to loose the tiny springs inside the switch) and replacing the thermal fuse.
• The cable has failed - see this page
• The cable socket has failed (mainly on later GHD 4.2 models) - see the type2 cable socket page. Check the contacts are making contact with the central pin and bend them slightly if they are not.
• A poor cable socket connection has generated a power surge that has damaged the microprocessor or some other component on the PCB. If non of the above apply then try a replacement PCB with a working microprocessor. We have some more information about PCB failures here.

Beep and the light comes on, but they do not heat up

• Both heater elements have failed - see this page
• PIC Processor failure. Replace the PIC processor with the correct version, available from our shop.
• Thermistor failure.

Beep Continuously and do not heat up

• They are too cold (below 5 degress C) - put them in a warm place and let them warm up gradually and try again.
• The R8 resistor (R8 or R11 on 4.2B/P and Mk5 models) has/have gone high in value or open circuit - see this page
• The thermistor is faulty - the bead has broken, a wire has broken or it is badly soldered - see this page
• The PIC processor (the 8 pin device on the PCB) pin has failed. The PIC will need replacing. Available from our shop.

Beep Continuously but may heat up

•  Check R8 and R11 resistors. Either may have gone high in value or be open circuit.

LED goes out and the irons Beep and restart

•  The irons may achieve near normal temperature and it will keep repeating until unplugged.
• Check and replace capacitor C1. The capacitor should measure around 220 nano farad. It has often been found to have dropped in value to 28 Nano Farad.

Beep during use

There is an intermittent connection which is causing them to momentarily power off and therefore repeatedly make the power on beep.

• Check the cable for damage. - see the cable page
• Check the cable socket is making a good connection to the cable. Also see the type 2 cable socket page.

Only one plate heats up

• The heater element on the thermal fuse side has failed - see this page
• The heater and the thermal fuse have been wired the wrong way round on the switch side - the heater wires go to the middle two terminals

Not Getting Hot Enough

• There is not enough thermal paste under the non switch side heater element (the one with the thermistor) so the ceramic plates are not getting hot enough.
• Faulty thermistor on the non switch side - see the thermistor page
• The PIC micro controller has been damaged somehow and needs replacing. Available from our shop.
• The element on the switch side is broken and that arm is staying cold.

Overheating

• The heater on the thermistor side has failed but the thermal fuse has not tripped yet - see this page
• The thermistor has come "unglued" from the heater element and is not measuring the temperature correctly - see the thermistor page.
• The thermistor is badly soldered (never seen this myself) - see the thermistor page
• The PIC micro controller has been damaged somehow and needs replacing. Available from our shop.
• The triac has gone short causing the heaters to be on all the time (never seen this myself)
• The heater and the thermal fuse have been wired the wrong way round on the switch side - the heater wires go to the middle two terminals

Buzzing / Humming / Sparking noise

This noise means that electricity is arcing somewhere in the straighteners. This is bad and you should stop using them immediately!

• Cable is failing (normally inside the strain relief) - see this page
• Cable socket pins are bent and not making a good contact. See the type 2 cable socket page.
• Switch contacts need cleaning. You can normally dismantle the switch if you are careful and give the contacts a clean.

Some other set of Symptoms not covered above

• Are you sure they are genuine GHDs? If you are, then send us an email.
• Or send them to us for repair. See our repair services page - https://www.ghd-repair.co.uk/shop/repair_services/

 

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