RR p38 HSE 4.6 1996

mikkre · Nov 17, 2023

Hello! I`m new here, but otherwise old. I am restoring a RR p38 4.6 HSE 1996 car. It has had a lot of restoration, from headliner to brakes, everything
in between. The car had all the common faults that i have fixed. Now I`M renovating the center console switch panel.
Now I ask: Does anuone have a wiring diagram for this panel? I would need information on part number C5, the capacitor.
Or does anyone have a meter that would tell the value of this capacitor.
I`m changing all the switches, except the mirrors, so I cut holes for them in the board.
I was a little unsure about it, and the Dremel cut a little too much, and that capacitor broke.
If what I`m saying sounds funny, it`s because of the Google translation. I don`t know enough English....
Thank you in advance, erkki from Finland.

Datatek · Nov 17, 2023

mikkre said:
Hello! I`m new here, but otherwise old. I am restoring a RR p38 4.6 HSE 1996 car. It has had a lot of restoration, from headliner to brakes, everything
in between. The car had all the common faults that i have fixed. Now I`M renovating the center console switch panel.
Now I ask: Does anuone have a wiring diagram for this panel? I would need information on part number C5, the capacitor.
Or does anyone have a meter that would tell the value of this capacitor.
I`m changing all the switches, except the mirrors, so I cut holes for them in the board.
I was a little unsure about it, and the Dremel cut a little too much, and that capacitor broke.
If what I`m saying sounds funny, it`s because of the Google translation. I don`t know enough English....
Thank you in advance, erkki from Finland.

I have a spare P38 switch panel, I will look later

Datatek · Nov 18, 2023

There are in fact 2 capacitors, the larger one is probably mustard coloured, it's a Tantalum bead electrolytic 100uf, when fitting a replacement be sure to get the polarity correct. The smaller one is blue on mine and 104K which will be picofarads.
IMO it's a shame to butcher the board when the existing switches can be easily fixed but what is done is done. @mikkre

mikkre · Nov 18, 2023

Thanks for the answer!! What I´m looking is a very small, wireless capacitor, C5. Pretty much in the middle of the board where components are. C% is located immediately below TR5 on the right. In teh upper left corner of the rear doors blocking switch. This capacitor is broken, and I would like to know the value
Switching in general, I replaced the switches so if they don´t start working, I switch them bypassing the BECM with normal wiring with a reverse connection. It only needs 2 wires to each door, plus a new fused power to the center console. I have thought that these small capacitors, 6 pcs (C2, C4, C5, C6, C11 and C12) with no connection wires, they are tinned directly on the boar, are very vulnerable, they can get a crack, in which case they do not do their job of filtering interference, and the IC messes up... Correct me if I´m wrong. Can these other wired capacitors break, but less often.

Datatek · Nov 18, 2023

mikkre said:
Thanks for the answer!! What I´m looking is a very small, wireless capacitor, C5. Pretty much in the middle of the board where components are. C% is located immediately below TR5 on the right. In teh upper left corner of the rear doors blocking switch. This capacitor is broken, and I would like to know the value
Switching in general, I replaced the switches so if they don´t start working, I switch them bypassing the BECM with normal wiring with a reverse connection. It only needs 2 wires to each door, plus a new fused power to the center console. I have thought that these small capacitors, 6 pcs (C2, C4, C5, C6, C11 and C12) with no connection wires, they are tinned directly on the boar, are very vulnerable, they can get a crack, in which case they do not do their job of filtering interference, and the IC messes up... Correct me if I´m wrong. Can these other wired capacitors break, but less often.

OK you must be talking about a surface mount device. Can you post a photo of the area and part you refer to? Surface mount devices rarely break although the solder joints may fail.
they way you are messing with the wiring sounds crazy to me.

mikkre · Nov 18, 2023

mikkre · Nov 18, 2023

Here's a picture. I have surrounded all the surface mount capacitors, but I only need information about the C5 capacitor, which is missing from that picture.

Datatek · Nov 19, 2023

mikkre said:
Here's a picture. I have surrounded all the surface mount capacitors, but I only need information about the C5 capacitor, which is missing from that picture.

I'll take a look tomorrow.

mikkre said:
Here's a picture. I have surrounded all the surface mount capacitors, but I only need information about the C5 capacitor, which is missing from that picture.

The value of C5 is not marked on the device and it is not possible to get an accurate reading with the equipment I have. I would guess it's about 100pf.
You say you are bypassing the BECM for window control, you do realise that you will lose the anti trap feature which will make the closing window potentially dangerous. You will also lose the lazy locking feature which enables to closing of all windows from the FOB when locking the car.

mikkre · Nov 20, 2023

Thanks for the answer! Yesterday I got a used switch panel from a Finn who read the forum.
After measurement, the result was C5 560pF. Measured while attached to the circuit board, in which case the result is not completely reliable. The position of C5 in the connection is such that its value is not very critical, I will try a 470pF ceramic capacitor for it.
As for the operation of the car's original switch panel, no matter how great it starts, it doesn't matter if the windows don't work, or they have to be repaired repeatedly.
I noticed that the mirror change switch can be opened. it's worth opening and cleaning, both panels were oxidized from the inside. The shifter has good contact surfaces.

Datatek · Nov 20, 2023

mikkre said:
Thanks for the answer! Yesterday I got a used switch panel from a Finn who read the forum.
After measurement, the result was C5 560pF. Measured while attached to the circuit board, in which case the result is not completely reliable. The position of C5 in the connection is such that its value is not very critical, I will try a 470pF ceramic capacitor for it.
As for the operation of the car's original switch panel, no matter how great it starts, it doesn't matter if the windows don't work, or they have to be repaired repeatedly.
I noticed that the mirror change switch can be opened. it's worth opening and cleaning, both panels were oxidized from the inside. The shifter has good contact surfaces.

After cleaning with contact cleaner/lubricant, the window switches on both mine are working fine, in one case for years.

RR p38 HSE 4.6 1996

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