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This controller is rather expensive so I had a go at fixing it. Opened out by prying open back cover. Both back cover and terminal plate is held on with black silicon sealant and fairly easy to pry open especially when heated in piping hot water first. Note that circuit board has to be lifted and heat sink clamp and screws must be removed before prying loose terminal plate from housing.


Above photo shows the internals of the controller (photo taken after repair). This one had a burnt out IRF 3205 TO-220 POWER MOSFET transistor causing glow plugs to remain permanently on and draining the battery.

In most cases one of the power MOSFET transistors will be burnt out and these are very easy to replace.
Using a multimeter, just measure resistance between the three legs on each MOSFET transistor to identify which is faulty. On mine all legs were shorted on one of the two MOSFET transistors.
The circuit board contains lots of surface mounted components. These are very tiny and therefore tricky to change out. A fully burnt out and shorted MOSFET transistor will not cause any damage to the circuit board as there is a 1K Ohm resistor between the gate and the board.


Circuit board needs to be lifted from the terminals and from the 2 MOSFET transistors. Use desoldering wick and perhaps a desoldering pump. You get access to remove the heat sink clamp and screws once circuit board is out. Pry out terminal plate and desolder the burnt out MOSFET transistor(s) and replace. It is advisable to use a heat sink clamp when soldering on the new transistor. Avoids burning out the transistor at time of doing repair.

A new IRF 3205 TO-220 POWER MOSFET transistor has been fitted and ready to be soldered in place. Thermal paste can be added to increase heat transfer from the transistors. There was no thermal paste on my controller so I assembled without.

Fit terminal plate containing heat sink and MOSFET transistors into the box having applied some silicon sealant to the joints.

Fit heat sink clamp and finally solder circuit board to terminals and transistors. Do a quality check of solder points and when happy apply silicon sealant to back cover and fit to housing. Hold temporarily with a clamp until set.
Important point: Only use non-corrosive silicon sealant.
Cost of parts 5 pounds. I bought 5 MOSFET transistors on eBay for 5 pounds delivered. Cost for one inclusive of delivery was nearly same as for five. Anyone needing any of these transistors, just send a PM.
 
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Discussion Starter #2

The easy way to check if the controller is burnt out is by measuring resistance between 12V supply and the two feeds to glow plugs. Resistance will usually be zero when burnt out. Controller will probably be OK if measured resistance is 500 Ohm or higher.

This fully working controller is for sale for 40 pounds or nearest offer. 8 pounds discount if you return the old one. Have also 4 spare power transistors. 3 pounds each or nearest offer. Burnt out power transistors can be replaced easily. Takes about an hour per controller for those that possess some skills in doing electronics repairs.

It is advisable to check cables to glow plugs in the event that a controller is burnt out. A short circuit will most likely burn out one of the power transistors before the fuse blows. The controller has two power transistors. These work like solid state relays switching power on and off to the glow plugs. Each power transistor switches two glow plugs.
 

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I know this is a old thread but do you know if the mosfets are the same in the 1.5dci maganes? They are the ones with the singular connector.

Regards
 
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