The Ford Barn

19ED30 · 01-22-2015, 08:05 PM

I posed this on the HAMB also ,

I have a pre 1955 electric cuved glass speedo with a round 3 pin plug ,
I have spent 3 hrs hear & on google looking for information on what type of
Sender used Or any wireing digrams or any photos , none found !!
I am trying to find out how the older ones worked & why they where used, Pre 50s
Does any one know where to look , No help at S&W tech line for the many thousands of gauges they have made for over the last 100 plus years .

Then I found this the other day on how the sender work (Round 3 pin connection)
For the Old S-W Electric Speedo & Tach that requires a sender 60's back
Not the square box sender.

The way that the unit is wired is that the gauge receives positive voltage on one of its three brushes, or phases. The sending unit has the alternate brush receiving negative voltage. When the gauge is turned, the voltage spikes and effectively doubles inside the sending unit creating an impulse or a rotation which the gauge decodes and turns into dial movement. In the past, I had wired the gauge by providing positive voltage to one phase, and negative to another brush on the sending unit side. This effectively created an instantaneous short because the two phases were shorting each other out instead of talking through the gauge to one another. When wired incorrectly the gauge was drawing over 5 amps of current. Now that it is wired correctly, as seen in my diagram, it draws about 0.55 amps in non working condition to power up the tachometer. When the sending unit is working, current draw jumps to ~0.75 amps which is in line with the little SW literature I have on this gauge. Finally, finally after all of this time I know how to wire this gauge! I am so excited and am sharing all that I know about this gauge for you to see. It is a model 760 tachometer and 762 sending unit.

Can any one add to this , S-W sender 762-A. Super ced to 762-G
This is a breakdown on the speedo / Tach , unable to find a breakdown on the sender !!
Anyone have old S-W Tech books or catalog's they can post ?
And a 762 image.jpg

Jim NC · 01-22-2015, 08:44 PM

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Contact Morris Gauge - he restores them. He is also on the H.A.M.B.

www.morrisgauge.com

01-22-2015, 08:05 PM	#1
19ED30 Senior Member Join Date: Mar 2011 Location: South of the Mason Dixon line Posts: 296	Stewart Warner Old curved glass gauges I posed this on the HAMB also , I have a pre 1955 electric cuved glass speedo with a round 3 pin plug , I have spent 3 hrs hear & on google looking for information on what type of Sender used Or any wireing digrams or any photos , none found !! I am trying to find out how the older ones worked & why they where used, Pre 50s Does any one know where to look , No help at S&W tech line for the many thousands of gauges they have made for over the last 100 plus years . Then I found this the other day on how the sender work (Round 3 pin connection) For the Old S-W Electric Speedo & Tach that requires a sender 60's back Not the square box sender. The way that the unit is wired is that the gauge receives positive voltage on one of its three brushes, or phases. The sending unit has the alternate brush receiving negative voltage. When the gauge is turned, the voltage spikes and effectively doubles inside the sending unit creating an impulse or a rotation which the gauge decodes and turns into dial movement. In the past, I had wired the gauge by providing positive voltage to one phase, and negative to another brush on the sending unit side. This effectively created an instantaneous short because the two phases were shorting each other out instead of talking through the gauge to one another. When wired incorrectly the gauge was drawing over 5 amps of current. Now that it is wired correctly, as seen in my diagram, it draws about 0.55 amps in non working condition to power up the tachometer. When the sending unit is working, current draw jumps to ~0.75 amps which is in line with the little SW literature I have on this gauge. Finally, finally after all of this time I know how to wire this gauge! I am so excited and am sharing all that I know about this gauge for you to see. It is a model 760 tachometer and 762 sending unit. Can any one add to this , S-W sender 762-A. Super ced to 762-G This is a breakdown on the speedo / Tach , unable to find a breakdown on the sender !! Anyone have old S-W Tech books or catalog's they can post ? And a 762 image.jpg Last edited by 19ED30; 01-22-2015 at 08:12 PM.

01-22-2015, 08:44 PM	#2
Jim NC Senior Member Join Date: May 2010 Location: SE NC Posts: 446	Re: Stewart Warner Old curved glass gauges Sponsored Links (Register now to hide all advertisements) Contact Morris Gauge - he restores them. He is also on the H.A.M.B. www.morrisgauge.com