70 Variable speed switch

[RJChallenger]

Hello every one. Ive got this variable speed switch , 450 date code. How much should the knob turn from slow to fast? My switch only rotates about 90 degrees. there only seems to be a click will turning the switch off. Is there a way of testing the switch with only a digital meter. thanks

[Cuda Cody]

Use an Ohm meter to check if the switch is working.

[RJChallenger]

My switch only rotates 90 degrees. Does a working switch rotate 180 degrees? or more.  Is there a test procedure  to bench test the switch .thanks

[headejm]

I assume you mean variable wiper switch? Mine acts the same way as you describe yours. A little more than 90 degrees with a "click" in the slowest position. No "click" in the fastest position.

[RJChallenger]

Great, So it would seem that the switch ( 2770380) functions mechanically as it should. Now I just need to find a way to test the switch itself. I don't have a wiring harness to connect to. The 450 on the switch is that week 45 of 1970? And lastly was this switch used on rallye dashes only, or was it also used on non rallye dashes as well?

[Slotts]

I always like using the technology designed at the time when working on a 60's or 70's car. A good old analog VOA meter with a sweep arm.

Trying to use a digital meter on an analog device is like trying to read a gas station pump when voltage or impedance changes. 

The knob turns a full 180 degrees, from off to the highest wiper speed. If your switch is only allowing a 90 degree travel, something is binding inside and I do not recommend trying to force it any further or internal damage will occur. I do offer a restoration service for these 2770380 switches.

All 70-71 Rallye clusters used the variable speed wiper switch. All 72-74 Rallye used a fixed three speed position switch. On a standard dash, a two speed wiper setup was standard and a three speed wiper setup was an option.

The 450 date code is the 45th week of 1970 which was probably from a 71 year car.

Attached is a testing white paper that I wrote to help with this switch and motor.

Jim
JS Restorations

[RJChallenger]

Thank you very much.  I will take the switch apart and clean lube the contacts. Unless i buy a 70 rallye wiring harness i'll never need this switch

[RJChallenger]

Thanks Jim for your assistance. I pulled the switch apart, grease was dried out . Cleaned the contacts a greased it all up. It seems to now rotate 180 degrees. Can a variable speed motor (3431624 with 0452 build date )  be controlled by a three spd switch or must it have a variable speed switch?

[Slotts]

Thanks Jim for your assistance. I pulled the switch apart, grease was dried out . Cleaned the contacts a greased it all up. It seems to now rotate 180 degrees. Can a variable speed motor (3431624 with 0452 build date )  be controlled by a three spd switch or must it have a variable speed switch?

That sounds good. Have you tested the switch for the impedance readings on the white paper that I attached?

A 2770380 variable speed wiper switch or a 3488764 three speed switch will drive an 077 type wiper motor. The 2770380 uses two connectors, a four position and a two position. The 348874 uses only one six position connector. Both types of switch change the ground resistance that is feeding the motor. There is nothing on the motor that can change any resistance.

The two speed wiper motor and switch is exactly the opposite. The resistance to change speeds occurs via the the mounted ballast resistor that makes the high speed. The 2947404 or 3488773 two speed switch do not have any resistance change capability.

Jim

[RJChallenger]

I haven't tested the switch just yet. I'm going camping this long weekend and I plan on bringing a few wiper motors and switches to play with and test.The trailer is 12v i should be able to sit at the kitchen table .

[RJChallenger]

Just got back from a camping trip with the wife, It rained all day saturday , which was good as it gave me a chance to polish the windshield chrome. I tested the wiper switch as per  your test it checks out good. the resistance on the slower end is a little eractic , but otherwise test OK. I also brought along (two) three speed wiper motors. Both motors tested OK and they even parked as they were supposed to do. AWESOME. Many thanks to Jim for his assistance in this indeaver, I have learned a little of what i forgot so long ago . thank you

[Slotts]

I have learned a little of what i forgot so long ago . thank you

Yea, back to Analog Land!

You're welcome. 

Jim