MG Rover Pektron SCU/BCU Relay Replacement Guide

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INFORMATION


PEKTRON SCU/BCU 
The Pektron SCU system was fitted  to following MG Rover Vehicles from Aug 2003 
  • MG/TF/ZR/ZS/ & ZR Express Van    
  • Rover 25/45/Streetwise
There are five relays on each Pektron SCU, as fitted to the above vehicles, and they all are prone to failure.

TYPICAL FAULT CAUSED BY FAILED RELAYS 

Central Locking - Locks but does not UNLOCK or unlocks but will not LOCK
Drivers Window - Goes up but not DOWN or down but not UP
Horn or Fogs - NOT working, or if the horn is Constantly ON
Windscreen Washers - Front or Rear NOT working
Intermittent Wipers - or Super Locking NOT working

LOCATIONS OF THE PEKTRON SCU/BCU IN THE VEHICLES

**WARNING**

Remove your battery negative terminal before removal and refitting and wait ten minutes to allow the airbag to discharge

MG ZR & ZR Express (Van) & Rover 25/Streetwise
Unit is located behind the Air Ducting (that is behind the glove box) and is attached to the rear bulkhead.
AirCon
If you have AirCon then its in the same place but more work is needed to remove it.

MG TF
Unit is located behind the heater controls on the central column.
Access to it is via either side but the easiest way is by the  passenger side, by removing the left passenger's right side kick panel (has a light in it) you will then see the Pektron SCU.

MG ZS & Rover 45
Unit is located behind the central column.
Low down and attached to the supporting metal framework.
The Central column facia has to be removed to access the Pektron SCU

REMOVAL INSTRUCTIONS
We can help with precise removal  instructions for the Pektron SCU/BCU for  each and every vehicle, these consist of text and pictures and are available via email from us.

We are not allowed to publish our email address here, so you will find it on the any of our eBay or relay pages .... RELAYS  or our main page HERE

Also glad to be of help via Tel 01792 896404

Our other contact details are at the bottom of this page.
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RELAY REPLACEMENT INFORMATION

The Pektron SCU is a multi-layered PCB with through plated holes (called Vias) which connect one or more layers to another (these boards have more than two layers)

What in effect happens, is when the relays are first soldered in the the solder goes some way down those holes and the pins and holes become as one. (The vias (holes) are thin copper tubes connecting the different layers together and often have a thin coat of solder.) This can make the relay difficult to remove.

The relays are not easy to remove without the proper tools. 

Using force to remove them, even with heat applied can damage the copper trace or the pads and also components on the PCB rendering it useless.

Overheating when removing or replacing can have the same effect.

 PEKTRON SCU/BCU with the RELAY IDENTIFICATION  as shown. Fig 1

Fig 1
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Pektron Relays - Part No 0662P04A (now Obsolete)

The original Pektron SCU relays were made by an American company and badged as 'Pektron' and numbered as part number 0662P04A - these you cannot buy direct from Pektron themselves - only as part of a new board..... 

We have sourced the same relays direct from the OEM (Original Equipment Manufacturers) that made the Original badged Pektron ones, and these are badged as 'DuraKool'.

These are part number DG08-7011-35-1012 and are the same HQ relay with the same footprint (9 pins) and twin internal  relays and rated to the same or higher spec.

Below is the Relay Schematic Fig 2, showing the twin coils. - Fig 3
And the New OEM DuraKool relays. 
Fig 2 showing the Relay Schematic and Fig 3 Showing the New relays from DuraKool
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Fig 2 showing the Relay Schematic and Fig 3 Showing the New relays from DuraKool
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Fig 2 showing the Relay Schematic and Fig 3 Showing the New relays from DuraKool

Ways to remove the Relays and tools used.

Below are pictures and instructions on the different ways to remove the relays.
Remember  that the Pektron SCU PCB can be damaged by static shock.

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SOLDER SUCKER AND SOLDERING IRON IN USE - Fig 4

                Get the Solder hot and molten - then SUCK the solder off the Pin
                You may have to re-solder the pins to enable you to get it all out.
                 Or use a combination of the sucker and Solder Wick - see below.
                                     Do not overheat the board, copper trace or pads.
Fig 4  Get the Solder hot and molten - then SUCK the solder off the Pin
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Fig 4 Get the Solder hot and molten - then SUCK the solder off the Pin

SOLDER WICK AND SOLDERING IRON IN USE - Fig 5

         50 Watt Solder Iron heats up the copper wick and SUCKS the solder up.
               Again you may have to resolder the joint to get it all off the pin
            Flux will help here to enable the solder to flow - flux pen or liquid.
                                 Do not overheat the board, trace or pads.
Fig 5 50 Watt Solder Iron heats up the copper wick and sucks the solder up
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Fig 5 50 Watt Solder Iron heats up the copper wick and sucks the solder up

CLEANED AND READY FOR THE NEW RELAYS - Fig 6

      The old relays have been removed and the holes cleaned of all solder.
              Do not push  the relays out or use force to pull them out.
  You can break up the relays bit by bit and try to cut the legs on the relay side.
       Using side cutting pliers  but this form of removal is not recommended.
           By far better to de solder the relays using only just enough heat and
                       the least amount of time on the joint to do the job.
Fig 6 Cleaned and Ready for the new relays
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Fig 6 Cleaned and Ready for the new relays

Soldering in the new relays......

You will notice that some of the copper areas that the through hole vias are on are bigger and more substantial than others - instead  of just a  small copper pad around the hole, with a small thin trace of copper attached, you may have a large section of copper with the hole and pad attached to it.  These need care when soldering as they will drain the heat quickly from the solder tip and make getting a good joint difficult.

You can overcome this by using a bigger soldering  tip, chisel type in shape, about the same size in diameter as the hole (3 -3.5mm) and  a soldering iron of 40 watt plus - 50 watt is ideal.

There are some through holes that have no visible copper trace to them, these are the easiest to solder and the fastest to do, but that also means if you are not aware then those are also the easiest to overheat!  As there is no large copper areas to draw heat.

Heat the joint by applying the tip to the pin and the pad at the same time, then bring the solder to the other side of the pin that the solder tip is on. As soon as it flows - check that it covers the pad area and a little way up the pin, then remove the solder and then the solder tip. You only want to be on the pad with the solder tip for the minimum amount of time to do the job.

Too much heat and time on the pads will delaminate the pad from the pcb material and or damage the pcb itself or the other components on it.

Use the thinner type of lead free or leaded solder 1mm or under - easier to work with, but the bigger stuff 1.5 can still be used.

BASIC TOOLS SHOWN BELOW FOR RELAY REMOVAL

        Whilst they are not the same as the Commercial tools that we use                                            (Pace/Hako etc)  which can remove these relays in seconds,
         those tools below are still as effective, but take longer to do the job.
Fig 7 Solder Wick
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Fig 7 Solder Wick

SOLDER WICK - Fig 7

This can be bought quite cheaply and comes in various sizes - you may find that 1.5mm or 2m is fine to use.

Used with Flux it can do a good fast removal job on the relays.
You will need a good soldering iron.

SOLDER SUCKER - Unheated - Fig 8

Various types of these are made - you want a good quality one not too big
and with a 2mm approx diameter on the sucking end.
Price about £6 -£10
Fig 8 Solder Sucker - Unheated
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Fig 8 Solder Sucker - Unheated

SOLDER SUCKER HEATED - Fig 9

A heated solder sucker that can make the job easier and faster.
Wait for it to heat up (5 mins Approx) then arm the suction, and then tin the tip.
Apply to the relay pin and wait for the solder to melt and hit the action button.
If you are lucky it all comes away clean - if not re solder the joint and do it again.

The tips do not last long. And keep the tool clean if you want to use it again !
Price about £15 - £20.

Fig 9 Heated Solder Sucker
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Fig 9 Heated Solder Sucker

PICTURES OF THE PEKTRON SCU

Here are some larger pics of the Pektron SCU unit before, during and after repairs.
Showing the old and the new Relays 

PEKTRON SCU Part No YWCOO1540  - Fig 10

Pektrons SCU unit Part No. YWC001540
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Pektrons SCU unit Part No. YWC001540

Petron SCU Printed Circuit Board (PCB) removed - Fig 11

Showing old relays in place 
Fig 11 Showing old relays on pcb
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Fig 11 Showing old relays on pcb

Reverse side of the same PCB - Fig 12

Notice the Radio Receiver Car (in white frame) that is easily damaged so take care.
Fig 12  PCB showing Radio Card from reverse angle
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Fig 12 PCB showing Radio Card from reverse angle

PCB with the Relays Removed - Fig 13

Shows the relays removed and unit cleaned ready to solder in new relays.
Fig 13  PCB showing old relays removed and ready for new
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Fig 13 PCB showing old relays removed and ready for new

PCB with new relays Fitted - Fig 14

New Relays fitted to PCB ready to get back in the case and re install in the car.
Can purchase these Relays HERE  on our eBay pages.
Fig 14 PCB with new relays fitted
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Fig 14 PCB with new relays fitted

PEKTRON SCU - Badly repaired/damaged.

A few pictures taken of Pektron SCU units that have been damaged while attempting to replace the relays... or altered to make them work...sent to us to sort out!

The First picture shows damaged pads and signs of overheating, two of the vias (holes connecting the layers had the copper liners ripped out.

The Second picture shows a similar item, this has been done by someone and they have damaged the vias and copper traces this time. Also the soldering is not good...

The Third and last one shows a sense of adventurism in that the person used a 10 pin relay to replace the normal 9 pin ones but then had to fit them anywhere but where they were normally meant to go...interesting..he had the  knowledge to get it to work.
Interesting ...........
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Interesting ...........
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Interesting ...........
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Interesting ...........

Who does the job in the end.........

Finally I should say a few words on who should attempt the relay replacement.

If you have no soldering or very little experience I would give it a miss.

If you want to have a go then go ahead, bear in mind what has been said above, take care and think it through first, then get all the tools in place, and better to practice on something else first!

If you do attempt it and get it wrong we can sort it out by either repairing the damage or cloning the unit to another (copy the active data IE fobs - Immobiliser start code for ECU and configuration data) to the replacement unit you source or we supply (second hand) that way you get a working unit back.

Or you can send it to us via mail and we can replace all the relays for £60 

Otherwise  you can purchase the 5 new relays on eBay from us HERE and do the job yourself for £25 inc postage paid.

Some commercial garages & customers try, and end up sending the results to us to sort out, but to be fair a lot manage it and sort it.

Lastly, it should be said, that there is absolutely no point in changing only one relay, UNLESS you are selling the car, as the the next relay to fail is not far away, it will always pay in the long term to change them all.

T4 Programming Available including Calibration & Matching

    ______________________________________________________________________

We accept no responsibility for any damage however caused - this guide is made available on the understanding that is only a guide and any works carried out using it are at your own liability. You can only use this guide if you accept this. 

MG2B01    Guide by Remobilise Ltd  © 2014                                                  Tel 01792 896404 


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