Negative earth wiper motor switch

[New Bloke]

I've converted to negative earth and all the sage advice seems to be you only need to flash the dynamo then switch the leads over on the battery, however, in my car we have this situation:
wiper motor
+-----------------2
E----/------------3
E------------------1

I've had to get a new motor that though it fits has slightly different terminal arrangements, so, I'm thinking I need to now wire the earth to the earth, then put a positive cable to ter 2 and switch another positive to get to ter 3.

The old motor is burned out, I believe by having a positive on ter 2 and a neg on ter3. I really don't want to burn this one out.

[New Bloke]

I don't think I explained myself very well there.

As I see it, when I switch the wiper switch on, it completes the connection between the terminal 1 (black and green wire) and the body. When the body was + this would have allowed a plus voltage on both terminals 1 and 2. Now the body is - it creates a dead short across the windings as terminal 1 is negative and terminal 2 is positive.

Am I right?

Cheers

Tim

[amgrave]

The wiper switching on a minor is done by switching the earth not the positive so you have a positive supply to the wiper motor all the time.

[New Bloke]

Thanks Amgrave,

I'm aware of that and wonder if that is in fact causing me the problem.

Cheers

[bmcecosse]

You don't do anything to the wiper motor or switch. You DO need to swap the coil connections and clean the points in the dizzy and the fuel pump.

[New Bloke]

Thanks Guys but the fact remains, if I leave the switch as it is I will end up with a positive on terminal 3 and when I switch on, a negative on terminal 2. That's what must have blown my first motor. Because the motor is insulated from the body, the original setup would have seen positive on T1, and neg on T2 & 3. So I can't understand why a polarity change doesn't bugger up everyone's wiper motor????

Odd

Tim

[New Bloke]

Please ignore absolutely everything above this post, just wired it back up and it works

Doh

[bmcecosse]

The wiper motor has both field and comm windings - so it is not in any way affected by polarity.............