Windsheild Wiper Motor Problem

[MGTF1250Dave]

Aloha All,

I completed rewiring my TR3A and most everything is working fine. I need to replace the stop lamp switch, the circuit tests ok and I have lights when I jump over the switch. My bigger problem is the wiper motor will not run. It did work properly before I began installing a new wiring harness. I have tested voltage at the motor connections and have 12 V, checked the ground connection, 0 ohms and disconnected the wiper drive to remove the load fronm the motor, but it still doesn't run. I disassembled the motor and cleaned the commutator and bushes, they had alot of gunk on them. The motor has two power connections a green wire (12V when the ignition is on and I'm quessing is the power supply to the parking circuit) and a black/green wire supply 12 V when the wiper switch is turned on. There is a black ground wire from the motor frame to the car body. The motor is provided with an adjustable parking circuit that stops the blades in the same position regardless of when the switch is turned off. Through experimentation by adjusting the parking position, I've discovered that I can get the motor to run for one revolution of the large drive gear until it returns the the park position. The wiring to the parking circuit becomes very hot and I've seen whisps of smoke from connection(the dome on the drive housing). It would appear that I have a short somewhere in that parking circuit. Does anyone have suggestions on further testing, rewiring the parking circuit or is it possible to remove it? Any help will be greatly appreciated.

I couldn't help myself, I took the car for short cruise around the neighborhood. I an anxious to fix these electrical problem to begin drive the Triumph regularly.

Safety Fast,
Dave

 

[MGTF1250Dave]

Aloha Again

A little dinner and a glass or two of wine must have stimulated my brain. I did a little checking and the wiper motor is probably from a TR4. The main difference between the the TR3 and TR4 motor installation is, the switch in the TR3 provides power, in the TR4 it provides a path to ground. I tested this by providing a ground connection to the black and green connection on the motor and it started running. The lesson to be learned from my experience is that with these older car some parts may look original, but are from later models. A check of a TR4 wiring diagram resulted in my epiphany. Tomorrow I'll make an "current" wiring diagram of the car for my future reference and any follow on owners. I think having a place and the opportunity to describe my problem was a great help in finding the answer.

Safety Fast,
Dave

 

[Geo Hahn]

Actually the 'ground-switched' wiper motors were original to most TR3As but the wiring diagrams usually encountered still show the old 'power switched' arrangement... so yours may well be the original motor.

If you haven't printed off a copy, this site has a link to some good wiring diagrams for the late TR3A (and others):

https://www.britishv8.org/techhome.htm

 

[MGTF1250Dave]

Re: Windshield Wiper Motor Problem

Aloha George,

Thanks for the assist. I'd downloaded those wiring diagrams after a some previous posts had referenced them. They were what cause my reaching a solution and getting the motor running. They are a good reference to follow changes from model to model.

I got a safety inspection and now the TR3A is "officially" back in service. I drove it to work today.

Safety Fast,
Dave

 

[Banjo]

Re: Windshield Wiper Motor Problem

Aha! those diags. are the missing links. That was the one thing that stumped me on those cars. I jerry-rigged one one time by clipping the wire to the park contact cap, and then you had to time when you shut off the wipers.I knew it wasen't right but it worked. These printouts will be going right in my shop library. thanks!

 

[txtr3]

Re: Windshield Wiper Motor Problem

I liked these drawings, too. Besides giving the variations for the different models, they are also much, much easier to read than the diagrams in the Triumph manual.

Anyone know where the power for the heater fan switch is connected on a 3A? It's left as an open question on the drawing. I'll track it down if I need it, but just thought if anyone's already figured it out...

 

[MGTF1250Dave]

Re: Windshield Wiper Motor Problem

Aloha txtr3,

I would suggest the you connect the heater fan control switch to the "A4" on the fuse box. You will probably need to run a wire from the box to the switch (green would be the standard color to use). An alternative would be to run a wire from the green wire power supply to the fuel gauge. IMO a separate wire to the fuse box is the better choice.

Safety fast,
Dave

 

[txtr3]

Re: Windshield Wiper Motor Problem

Aloha Dave,
I agree, separate wire to the fuse box is the best choice, if you're connecting one up.

What I meant to ask was, "how was it actually connected, on cars where this option was fitted?"

More out of curiosity... Mine's working ok, so I haven't traced the connection, but I just hate having this nice schematic where everything's clear except this one connection.

 

[MGTF1250Dave]

Re: Windshield Wiper Motor Problem

Aloha,

I just installed a new wiring harness in my TR3A. The green wire that feeds power to the fuel gauge had a second wire coming from the connection. This may well have been the source of power for the heater fan motor?switch circuit. I don't have a heater installed in my car.

As for the diagrams, I've added to the standard diagram all the modification I've made (I have an electric cooling fan added) so I have an "as is" wiring diagram for my car. This I think will be of good use in the future for either myself or the next owner.

Safety fast,
Dave

 

[Geo Hahn]

Re: Windshield Wiper Motor Problem

Dave - Do you have/did you add an inline fuse behind the center dash to protect the lights? These were fitted to US cars only -- not sure at what point it was added but isn't always included in the harnesses sold.

AFAIK it was between the main (side/head) switch and the panel light switch. Protects the tailights/parking lights/instrument lights... not the headlights of course. They are 'protected' by the wiring harness melting if something goes amiss there.