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20171114_163757_1510677543329_resized.jpg
2012 Plus 4 Dash Module Heater Fan Diodes
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Poster Nickplus4 Offline
Posted 14/11/17 04:52 PM
Description
Following on from my thread from the Maintenance section, here is a pic of the board and then my sketch of the circuit - I have traced the heater fan connections as best I can with meter and Mk 1 eyeball. I have yet to check on my repaired board but as I understand it from KH, D6 and D7 are the diodes that have failed and caused the 5A fuse to blow so I lost the heater fan, speedo sensor and dash panel background lighting. These pics are of the failed board.... I have guessed that the top right 15 pin connector connections are the low current +5V and earth supplies for the relay switching are that way round - doesn't make sense otherwise (need to check on the loom diagrams later though).
No warranty given if you mess about with your board... top right is a microcontroller with embedded software, and behind are a pair that look a bit like FGPA chips so it's a scary place to wield a soldering iron!
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#482848 - 14/11/17 04:53 PM Re: 2012 Plus 4 Dash Module Heater Fan Diodes [Re: Nickplus4]
Nickplus4 Offline
L - Learner Plates On

Registered: 03/10/16
Posts: 234
Sorry that was not clever was it - you need to rotate the first image 90 degrees anti clockwise to get the equivalent of the diagram

Nick

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#482908 - 14/11/17 09:50 PM Re: 2012 Plus 4 Dash Module Heater Fan Diodes [Re: Nickplus4]
Paul F Offline

Has a lot to Say!

Registered: 20/08/10
Posts: 1432
Loc: Costock, South Nottinghamshire...
Those smaller diodes look a little under size.

Good luck with the detective work.

Would love to know what the marking on the chip is - curiosity and all that.


Edited by Paul F (14/11/17 10:01 PM)

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#482937 - 15/11/17 04:12 AM Re: 2012 Plus 4 Dash Module Heater Fan Diodes [Re: Nickplus4]
Richard - Aus Offline

Member of the Inner Circle

Registered: 15/01/12
Posts: 14370
Loc: Perth, WA, Australia
Good luck!
_________________________
Richard
1976 4/4 4 Seater

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#482974 - 15/11/17 09:46 AM Re: 2012 Plus 4 Dash Module Heater Fan Diodes [Re: Nickplus4]
Nickplus4 Offline
L - Learner Plates On

Registered: 03/10/16
Posts: 234
Well this is now my backup board so I am using it to educate myself. And hopefully repair as a spare. I'll be looking at other parts of the board in due course - easy bits first like hazards and rear fog light.

The IC top right is a PIC16F818-I/P microcontroller. I am wondering if it is a controller for the air conditioning given it's position on the board. My other thought was speedo sensor but I understand that is a box in the engine bay by the main ECU.

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#483080 - 15/11/17 06:11 PM Re: 2012 Plus 4 Dash Module Heater Fan Diodes [Re: Nickplus4]
Paul F Offline

Has a lot to Say!

Registered: 20/08/10
Posts: 1432
Loc: Costock, South Nottinghamshire...
Originally Posted By Nickplus4


The IC top right is a PIC16F818-I/P microcontroller. I am wondering if it is a controller for the air conditioning given it's position on the board. My other thought was speedo sensor but I understand that is a box in the engine bay by the main ECU.


Air Conditioning sounds feasible. Possibly to manage a start sequence?
_________________________
Paul
Costock, UK
2014 4/4 Rolls Royce Garnet Red - Ruby Mog, Disco 4, Teddy - 17h1 Irish Draught cross

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#483206 - 16/11/17 02:16 PM Re: 2012 Plus 4 Dash Module Heater Fan Diodes [Re: Nickplus4]
Rog Offline

Talk Morgan Regular

Registered: 31/05/12
Posts: 663
Loc: Sumerset
A wild guess but I believe these cars might have an early type of can-bus system for instrumentation etc. The pic might be used for that?
Good luck Nick smile
_________________________
Roger
2006 4/4 Duratec

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#483726 - 18/11/17 06:25 PM Re: 2012 Plus 4 Dash Module Heater Fan Diodes [Re: Nickplus4]
milligoon Offline
Talk Morgan Expert

Registered: 20/04/14
Posts: 2299
Loc: Dorset, UK
Those are the relay flyback diodes, the data sheet on the G5LE-1-E relays state around about 33.3mA current is present in the continuous draw to hold the relay on.

As long as the replacement diode can handle that (when it releases the current flows away through the diode to save having a voltage spike) it should be fine.


I think I'll be swapping mine out while it is still working I'll do the same for all the relay diodes.

Cheers for the info.
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Mark - driving
Archie the Old English Sheep Mog...........
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