Windscreen wiper motor high speed fault 1963 XKE

I have a little challenge in the way that my windshield/windscreen wiper motor refuse to go on high speed unless motor is hot. When first hot it goes on high speed low speed up and down nicely. Selfparking is working as it should.
When cold and set the switch in high speed in suddenly goes in high speed. Any ideas?

I finally just disconnected mine as I never drive in the rain . A very temperamental system

Had you re-wired the motor at anytime in the past? If not, it is possible the connections internally are growing corroded and require some heat to make connection?

It’s likely the brushes are worn out. And something expands enough to make contact when hot… I believe New brushes are available. You may have to buy all three of them on Their support plate

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Brushes are OK, more or less like new. I only have two brushes, the way this reduces speed is to run current throygh a resistor. Just like coupe fan motor. But I will bring your point to my Jaguar electrician tomorrow.:blush:

I have replaced all external wiring going into motor. Job done by a professional. But I will bring your point to my Jaguar electrician tomorrow. It seems like something has to be overcome by the heat in the motor. Once that has happened everythings work smoothly, high speed, low speed parking, everything. I will keep you posted what we find out tomorrow.:blush:

Maybe the problem is in the switch that changes resistance as it warms up. Either way, I would think some time with a volt meter, starting when it is cold, should help resolve the issue.

Hi, little silly question maybe, but how do I measure the voltage on the switch?

You would put one lead of the voltmeter to the car body metal someplace, like one of the gauge bracket posts. Then use the other lead to measure voltages. First verify you have a good body connection by probing a fuse of a light switch to make sure the meter reads about 12V. Then you can probe the wiper switch. With the ignition switch ON, you should see 12v on at least 1 terminal. Then turn on the switch and check terminals again. After it quits check check voltages again. If the switch is going open circuit then the voltage will drop on a terminal.

Hi, thank you for your advice, now I did what was proposed above in this little trail. The white cable should be normal speed of the motor. So when motor is cold it reads 11,4 Volts, testing on switch terminals. Irrespective of high or low speed position in switch.
Nothing (0,04) in the yellow that should be for the high speed. Then wiper motor get hot and suddenly the high speed works, then up and down fast slow fast slow on the switch all works good. The difference now is that the white Voltage increase to lets say 11,6 or something. But yellow cable just 0 0r 0,04 volts something. So is then the switch faulty?

One can troubleshoot in many ways. One could start at the switch and go to the motor, or start at the motor and go to the switch. I am going to start at the motor. Since you have a 3.8 S1, I will assume you have positive ground and I assume I am using the proper diagram. If not, switch my instructions for meter leads. Place your positive volt meter lead on a positive ground, and check the voltages with your negative meter lead.

  1. I suggest you disconnect one of the small wires at the ignition coil so the coil will not overheat while you have the key switch on for troubleshooting.
  2. The green wire comes from the fuse 7 and is 12v with the key on. So check the green wire at the wiper motor- should be 12v whenever the key is on.
  3. The blue wire exits the motor after the thermal switch. Check that it is 12 v and remains 12 v throughout your testing. In the motor, it feeds power to the armature.
  4. Now, with the switch off, you should have 12 v at the red wire if the brushes and the armature are good.
  5. Since your problem is in high speed, turn it on high speed. Now the red wire should go to 0v since it should be connected to the positive ground by the switch.
  6. The white wire should be 12v since the switch should be connecting it to 12v feed (negative).
  7. The yellow wire should be 0v. But this can be misleading. First check with your black lead to see if it is 0v. Potential problem is, it could read 0v because it is open. To be sure, connect your black meter lead to the battery, then connect your red lead to the yellow wire and it should now read 12v.
    Let us know.

Here is the diagram I used that I found on the forum. It appears to be correct for a 3.8 S1, and apparently it is curtesy Paul Ward.

(I hope someone checks my work.)


Thank you for your input. My earth has been changed to negative earth, but I did the checking as you explained above. Then I used my contacts here in Norway and discussed what it could be. Suggestions were two fold, either a faulty resistor or bad contact with the resistor. Another theory was a faulty thermo switch. I ended up sending it to UK for complete overhaul. Cox Auto Electronics I think the company name was. They also agreed on the most likely fault cause. So we shall see, in three weeks I get it back.:blush:
100% overhauled.