Technical Information

Fixing A Pektron SCU

If you have a late model ZR, ZS or a TF with the oval key fob as in the picture then some or all of these problems may be familiar:

1) Central locking will lock but not unlock or the other way around
2) The driver’s window goes down but not up or again the other way around.
3) The intermittent wipers or the wash/wipe doesn’t work

These problems are very often caused by a fault with a box called the Pektron SCU. I think it stands for Security Control Unit. It is in essence a small computer that handles security and the functions mentioned above. This board contains five relays which have a habit of failing. If this happens the obvious thing is to replace the SCU, but things aren’t that simple. Firstly, the unit contains all the programming options that were put in when the car was new.

These options include whether you want one click or two to engage super locking, how you want the drivers window one press open to work, and how many times you want the wipers to sweep after using the washers. All these options would have to be re-entered. But it doesn’t stop there, the SCU is security coded to the key fobs so if you replace the SCU you will almost certainly need new key fobs. The SCU is also security coded to the engine management unit. To set up this pairing requires specialist equipment. The alternative would be to get second hand unit and a complete set of key fobs, SCU and ECU.

Fortunately, there is another option, this is to repair the existing SCU. The advantage of this is that it does not affect any of the programming or the security coding. The repair is simply done by replacing the errant relay with a new one. Replacement relays are available via the internet or mail order. I have found at least two companies that can supply them. If you are reasonably handy with a soldering iron the job is straight forward. If you are not all is not lost as both these companies will do the work for you for a fee many times cheaper than having a new SCU installed.

To repair the SCU you will first need to extract the unit from the car this can be fiddly but not too difficult. One point to note is that the electrical connectors snap into place and you will need to release the clip by gently squeezing. They should then pull out easily. You now need to decide if you are going to repair it yourself or send it off to be fixed. If you decide to do the job yourself, you firstly prise off the plastic cover. To do this gently ease off the tabs surrounding the cover with a flat headed screwdriver. Once the board is out you can then replace the errant relay(s). The diagram shows the relays and their functions so you can choose which to replace. You will need a small soldering iron, a solder sucker or solder removing wick to remove the solder from the old joints. Be careful not to heat damage the board. Once the old solder is removed from the pins, with some gentle persuasion, the old relays can then be prised off the board. The pins on the new relay then push into the holes on the board left by the faulty relay and then pushed home. Then just solder the new relay in place. All you need to do is replace the unit into the car.

Below are the details of the companies I have found who can supply the relays or service the board for you:

E-mail: paul@technozen-electronics.co.uk

Technozen Electronics
44 Meadowview
East Sussex

Tel: 07527 877995

E-mail; info@remobilise.co.uk

79 Frampton Road

Tel 01792 896404

Fixing a blown heater resistor

It’s the time of year when your car heaters and blowers go into hyper-drive clearing your windscreens on those cold and frosty mornings. I know some ZR owners have had problems with failing resistor packs causing some of the fan settings not to work. I include myself here as settings one and two stopped functioning during January on my ZR. New resistor packs are readily available from various companies, and also online from either Amazon or Ebay where they can be purchased quite cheaply. Alternatively the individual blown resistor can be replaced independently if you prefer. There are many websites and forums online which give a step-by-step guide on how to replace the pack. I won’t steal anybody’s thunder by going through each stage here, but the task is very straight forward and well illustrated on some forums. Good luck.