p38 transfer box

[scoobie]

Hi to all first post on here! can anyone help me with the ratio control motor on p38 rr ,it has blown the ecu three times!!!! £150 a time !!!! and i refuse to replace again!! im not too bad with electrics but need to know how to hardwire the motor from a live feed, i would like to use the original switch if poss. but how do i up the amps past the switch? i've had the motor off a couple of times and got it to work with a direct feed from the battery, i have also changed to coil suspension so dont need to worry about the settings here. any info would be appreciated thanks. im not very good with forums so i hope i haven't offended anyone.

[David Sparkes]

I suspect that you need the wiring diagram from the Electrical Troubleshooting Manual (ETM), this is included, as well as the Workshop Manual, on the RAVE disc for the 38A, which is available 'free' as a 600ish MB Image File download from the Green Oval site.

You then have to convert this to a playable CD, although the RAVE application will work faster if you copy all the files from the CD onto your hard drive. RAVE.exe starts the application.

As you have probably found already, there are only two power wires to the motor, the polarity of these are reversed to drive the motor the other way IE Into or Out of low ratio. The other wires to the motor are from the position switch, these enable the ECU to know where the motor is, so it can decide whether to drive the motor forward or backward.

I'm not saying you can't create a totally manual control, which I think is what you are intending, but I'm not quite sure how you will tell whether the gear is fully or partially engaged.

You mention the original switch; should we conclude it is an car with a manual gearbox?

This is a locking switch, so can be treated the same as a switch on an automatic gearboxed car. You are right to think the switches won't stand the current drawn by the motor, but neither will they do the polarity reversal that is required.

There may be a relay already in existance that will do this reversal without shorting out the power feed, but I don't know exactly where to suggest. Vehicle Wiring Products perhaps, or a supplier to Kit Car builders.

For the actual power source, pick up the existing source, which is probably fed to the Transfer box ECU via the BECM, but without tracing the diagrams I couldn't say exactly.

HTH.

[scoobie]

I suspect that you need the wiring diagram from the Electrical Troubleshooting Manual (ETM), this is included, as well as the Workshop Manual, on the RAVE disc for the 38A, which is available 'free' as a 600ish MB Image File download from the Green Oval site.

You then have to convert this to a playable CD, although the RAVE application will work faster if you copy all the files from the CD onto your hard drive. RAVE.exe starts the application.

As you have probably found already, there are only two power wires to the motor, the polarity of these are reversed to drive the motor the other way IE Into or Out of low ratio. The other wires to the motor are from the position switch, these enable the ECU to know where the motor is, so it can decide whether to drive the motor forward or backward.

I'm not saying you can't create a totally manual control, which I think is what you are intending, but I'm not quite sure how you will tell whether the gear is fully or partially engaged.

You mention the original switch; should we conclude it is an car with a manual gearbox?

This is a locking switch, so can be treated the same as a switch on an automatic gearboxed car. You are right to think the switches won't stand the current drawn by the motor, but neither will they do the polarity reversal that is required.

There may be a relay already in existance that will do this reversal without shorting out the power feed, but I don't know exactly where to suggest. Vehicle Wiring Products perhaps, or a supplier to Kit Car builders.

For the actual power source, pick up the existing source, which is probably fed to the Transfer box ECU via the BECM, but without tracing the diagrams I couldn't say exactly.

HTH.

many thanks david will try hunting down some more info and let you know when i finish the job!!!!