p38 fuse box following conversion from petrol 4.6 to diesel 2.5

steveshone · Dec 7, 2023

Hello and apologies if this is not in the correct section have an ongoing project with my 1996 p38 HSE, I removed the worn out 4.6 v8 and replaced it with the 2.5 diesel m51.

I now have it up and running and everything works as it should apart from the de-mist function if I turn on the blower fans using the round dial on the hevac panel they work but not when using the de mist program button,

The other issue I have is regarding fuse 23 in engine bay fuse box which keeps blowing, but by disconnecting the wire supplying the drivers side front heated screen the fuse remains intact, I have checked the wiring thinking perhaps it was shorting to earth but it isnt

Before the conversion everything worked as it should but during the conversion I had to change the under bonnet fuse box for one off a diesel, but I am wondering if that is compatible with HSE spec as I believe there is a choice regarding this fuse box on diesel vehicles?
if this is the case does anyone know what fuse box should be used

Any ideas would be greatly appreciated

Datatek · Dec 7, 2023

steveshone said:
Hello and apologies if this is not in the correct section have an ongoing project with my 1996 p38 HSE, I removed the worn out 4.6 v8 and replaced it with the 2.5 diesel m51.

I now have it up and running and everything works as it should apart from the de-mist function if I turn on the blower fans using the round dial on the hevac panel they work but not when using the de mist program button,

The other issue I have is regarding fuse 23 in engine bay fuse box which keeps blowing, but by disconnecting the wire supplying the drivers side front heated screen the fuse remains intact, I have checked the wiring thinking perhaps it was shorting to earth but it isnt

Before the conversion everything worked as it should but during the conversion I had to change the under bonnet fuse box for one off a diesel, but I am wondering if that is compatible with HSE spec as I believe there is a choice regarding this fuse box on diesel vehicles?
if this is the case does anyone know what fuse box should be used

Any ideas would be greatly appreciated

There are at least 2 versions of the fuse box for the diesel but the later version really only affects starting. I do not know what differences there are between petrol and diesel wiring harnesses but probably quite a few. As for the heated screen, the element may just be drawing too much current for the fuse. Does fuse 23 power anything else?

steveshone · Dec 7, 2023

hi yes it powers the srs, that's how I first noticed the issue, thing is though before the conversion everything worked as it should with the original v8 fuse box, with the drivers side heated screen disconnected under the scuttle the fuse remains intact and sis works, as you say there are a lot of differences between the harnesses petrol vs diesel, I had to remove some wiring from the v8 cruise control and and replace it with replacement wiring to enable cruise via the diesel ecm, and also make a loom for the throttle potentiometer but I was quite meticulous when I started on the conversion wiring and all the connections where from plug / pin number too its corresponding plug/PIN number following the electrical repair manual, I have considered that there may be an internal fault with the fuse box, I will have a look what the part number is on my fuse box and have a look for another version/part number

steveshone · Dec 7, 2023

just had another look at the fuse box diagram, fuse 23 is srs, and blows as soon as I plug in the drivers side heated screen which is strange because the fuse for the heated screens is fuse 30, so perhaps there is a fault/short within the fuse box

DanClarke · Dec 7, 2023

I think we have found the issue. "conversion from petrol 4.6 to diesel 2.5".
This is a bound to cause "Christine" to get upset. She was born a 4.6 V8 and wants to be a 4.6 V8 not a pussy little 2.5 Diseasel.

steveshone · Dec 8, 2023

That could explain the issue with the headlights and radio turning themselves on?

Mark Piercy · Dec 8, 2023

DanClarke said:
I think we have found the issue. "conversion from petrol 4.6 to diesel 2.5".
This is a bound to cause "Christine" to get upset. She was born a 4.6 V8 and wants to be a 4.6 V8 not a pussy little 2.5 Diseasel.

mystery · Dec 11, 2023

Have you checked the right heated screen relay

p38 fuse box following conversion from petrol 4.6 to diesel 2.5

steveshone

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Datatek

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steveshone

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steveshone

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DanClarke

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steveshone

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Mark Piercy

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mystery

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