P38A Electrical Short , how to find it ?

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
MatP38

MatP38

Member
Posts
28
Location
Byron Bay
HI ,

I have a 1998 p38 petrol and the RH door module resistors are burnt out . Initially the electric windows were not operating so I replaced the corroded switch pack and 3 out of four started working again, just the RH drivers side was not functioning . So I chased the problem back to the motor , took it apart and cleaned the copper connectors hooked it up to power and it to was working . So I worked back to the RH module and found the problem ( or so I thought ) I had three brunt out resistors , so I took them to be replaced , plugged the repaired module back in and zap , resistors burnt out again. Now I need to locate where the fault is coming from .

Does anyone have and information to help me with my problem ?

Thank you .

Matthew
 
First place I would look is the wiring between the door and the door frame were the wires pass through the rubber tube.
I've seen wires break after years of opening and closing.
Is the anywhere inside the door where wiring loom could be rubbing or earthing out against the window mechanism?
Meter time!
 
Do you know where the resistors were in the circuit? I'll have to dig out a spare outstation to have a look.

There are 2 power feeds to the outstations - one is for the outstation itself, the mirror, and the door lock - and to control the electronics/relays etc.
The second is (from memory) solely for the window - which is controlled in the outstation via a relay.

F22 (30A) is the one that is for the window (but it's shared with the LHF window) and F9 (20A) is for the outstation and it's electronics (also shared with the LHF outstation).

So whilst power does come from the BECM, the fact that the fuse hasn't blown and the LH window etc works, says to me the issue is definitely somewhere in the door.

If you disconnect the window motor, does the relay in the outstation click when you press the up/down buttons for the RHF window? It could be there is another faulty part in the outstation which is causing the issue on the output stage.

It is worth checking at the outstation plug to make sure there is power on both the Purple/Blue (windows) and Purple/Black (outstation) wires. Also worth checking a good connection to ground on both Pin 7 and 9 of the main outstation connector as they are both of the ground connections.

If I've got time tomorrow, I will have a look and find one of my spare outstations and see if I can trace what resistors etc do what and the wiring to the window motor.
 
Wow , you are a well of knowledge ! Thank you for your help . Ill look into what you have suggested .

Thank you !
 
martyuk said:
Do you know where the resistors were in the circuit? I'll have to dig out a spare outstation to have a look.

There are 2 power feeds to the outstations - one is for the outstation itself, the mirror, and the door lock - and to control the electronics/relays etc.
The second is (from memory) solely for the window - which is controlled in the outstation via a relay.

F22 (30A) is the one that is for the window (but it's shared with the LHF window) and F9 (20A) is for the outstation and it's electronics (also shared with the LHF outstation).

So whilst power does come from the BECM, the fact that the fuse hasn't blown and the LH window etc works, says to me the issue is definitely somewhere in the door.

If you disconnect the window motor, does the relay in the outstation click when you press the up/down buttons for the RHF window? It could be there is another faulty part in the outstation which is causing the issue on the output stage.

It is worth checking at the outstation plug to make sure there is power on both the Purple/Blue (windows) and Purple/Black (outstation) wires. Also worth checking a good connection to ground on both Pin 7 and 9 of the main outstation connector as they are both of the ground connections.

If I've got time tomorrow, I will have a look and find one of my spare outstations and see if I can trace what resistors etc do what and the wiring to the window motor.
Click to expand...
 
@martyuk "If you disconnect the window motor, does the relay in the outstation click when you press the up/down buttons for the RHF window? It could be there is another faulty part in the outstation which is causing the issue on the output stage."

Yes there is a clicking in the out station when up/down RHF window button is pressed , I noticed this before I disconnected the window motor. Not sure if it does it when motor is not connected .
 
OK - I'll have to dig out a spare outstation here and see how the circuitry works. If you can get a picture of the board you have/burnt out resistors then it gives me something to go on.

It should click with the window disconnected too. But that just means that the control side is working - I am guessing the issue is on the power feed side either to the relay contacts (from the Purple/Blue wire) or from the contacts to the motor - but without a bit more investigation I couldn't pinpoint it for sure.
 
o
martyuk said:
OK - I'll have to dig out a spare outstation here and see how the circuitry works. If you can get a picture of the board you have/burnt out resistors then it gives me something to go on.

It should click with the window disconnected too. But that just means that the control side is working - I am guessing the issue is on the power feed side either to the relay contacts (from the Purple/Blue wire) or from the contacts to the motor - but without a bit more investigation I couldn't pinpoint it for sure.
Click to expand...
ok I will get you a pic asap
 
martyuk said:
OK - I'll have to dig out a spare outstation here and see how the circuitry works. If you can get a picture of the board you have/burnt out resistors then it gives me something to go on.

It should click with the window disconnected too. But that just means that the control side is working - I am guessing the issue is on the power feed side either to the relay contacts (from the Purple/Blue wire) or from the contacts to the motor - but without a bit more investigation I couldn't pinpoint it for sure.
Click to expand...
The burnt out resistors are TR1 and TR3
 

Attachments

  • IMG_7652.JPG
    IMG_7652.JPG
    345.3 KB · Views: 131
  • IMG_7653.JPG
    IMG_7653.JPG
    333.6 KB · Views: 122
TR1 and TR3 will be Transistors, rather than resistors.

I managed to dig out one of my spare outstations today - so will have a closer look at what they do tomorrow once I've had some sleep!
I'll let you know what I can find by having a look at one here...

Marty
 
martyuk said:
TR1 and TR3 will be Transistors, rather than resistors.

I managed to dig out one of my spare outstations today - so will have a closer look at what they do tomorrow once I've had some sleep!
I'll let you know what I can find by having a look at one here...

Marty
Click to expand...
Hi Marty , thanks for your help . I just incountered another issue with the truck . It wouldn't start (immobilised error ) so I keyed in the code to the drivers door and she fired up in park but when I tried to put it into drive it would not enguage , then when I tried to put it back in park it gives a plastic cap gear grinding sound and will not go into park . Any ideas ? She is really giving it to me !
 
MatP38 said:
Hi Marty , thanks for your help . I just incountered another issue with the truck . It wouldn't start (immobilised error ) so I keyed in the code to the drivers door and she fired up in park but when I tried to put it into drive it would not enguage , then when I tried to put it back in park it gives a plastic cap gear grinding sound and will not go into park . Any ideas ? She is really giving it to me !
Click to expand...

I'd start a new thread for this.
 
OK, had a quick look at this, and TR1 and TR3 appear to be part of the driver circuitry for the superlocking motor.

The fact they have blown again, seems to make me wonder if there is either bigger problem in the outstation, or whether there is a fault with the door latch which is killing the transistors.

The Siemens relay is the one that does the window motor, and if it's clicking when the button is pressed in either direction, then that part of the outstation is working.

Have you tried using a multimeter on pins 8 and 16 from the main outstation connector (Grey/White and Grey/Green wires) to see if you get 12V back out of the outstation when the window button is pressed? You should get +12V on a digital multimeter in one direction, and -12V in the other direction (reverse polarity).

If you don't get this, then I would be back to checking the power wire that comes into the door loom that runs the windows (Purple/Blue).

The relay itself is driven by one of the chips on the board, and the coil is provided 12V from the other power source (Purple/Black). So a lack of 12V on Purple/Blue at the outstation will cause the window not to work, but the relay still will.

Regarding the blown transistors - the don't appear to be connected at all to the window mechanism - and are probably a separate issue on the board.

I hope this helps narrow the window issue down though.

Marty
 
You must log in or register to reply here.

Similar threads

I
L322 ABS query
Replies
0
Views
514
isamyku
I
Blob
L322 2010-2012 Air Suspension Module location (I've found it!)
Replies
0
Views
990
Blob
Blob
deangermouse
HDC fault
Replies
2
Views
762
deangermouse
deangermouse
cornishboater
P38A Simple EAS query
Replies
14
Views
737
pwood999
pwood999
G
P38A 99 4.6 Thor with ABS&TC lights, no speedometer
Replies
7
Views
882
Andy Burrell
Andy Burrell
Back
Top