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'49 F-1 pickup temperature sender question


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I didn't see any clubs for the Ford truck, so was wondering if the wiring for the temperature sender units on the flathead V8 are the same for car & truck. An acquaintance just bought a '49 Ford F-1 pickup with flathead V8. It has 6v positive ground, and the temp gauge reads past the "H" when fully warmed up. A mechanical gauge was installed without disturbing the wiring to the two sender units and read only 180 degrees while the dash gauge was pegged past the "H". So we know it isn't running hot. When looking up sender units at NPD (and others), we noticed two senders; one with two spade type contacts and one with only one contact, but not spade type. Both sender units in this truck are of the two spade type. The passenger sender has both spade terminals utilized, the driver side sender only one. The passenger sender has one heavy wire and one lighter wire going to it. The driver side sender has one heavy wire attached. Both senders have one long and one short spade terminal, and both senders have the heavy wire going to the longer terminal. The lighter wire goes to the shorter terminal on the passenger side sender.

Is the heavy wire attached to the longer terminal of both senders the same wire? Is having the same sender on both sides of the engine the problem here? Why are there two senders and only one dash gauge? If a sender or water pump failed on one side of the engine, how would you know with only one gauge giving you a read out? I have neither a wiring schematic nor a shop manual for this vehicle, so not sure if wires are going to the correct terminals or not. Is there anyone out there who knows about these senders (and corresponding wiring) and might be able to shed some light on this subject for someone who has no experience with Ford flatheads?

Dave

Hobe Sound, FL

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There should be on sender with one terminal and one sender with 2 terminals. The one terminal sender will vary with the temperature allowing the gauge to indicate the correct temperature. The 2 terminal send is an over temperature switch, when the engine reaches boiling point, the contacts inside the sender open and the gauge will read hot.

One or both of your friend's senders are opening when the temperature is below boiling. The correct sending units can be bought from many of the Early Ford V-8 vendors. They are the same as the car sending units.

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To 19tom40:

The correct sending units were purchased from NPD and installed. Now the temp gauge reads cold all the time even when fully warmed up. The owner did show me an old worn out copy of the shop manual, and I did find a picture of the two sending units showing their relationship to the gauge. However, the drawing simply shows a wire going from the single contact sender to one of the two contacts on the two contact sender, and another wire going from the other contact on the two contact sender to the gauge. What the manual does not specify is which contact are each of the two wires going to. Does it make any difference which wire goes to the short terminal, and which wire goes to the long terminal of the two terminal contact?

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  • 3 weeks later...

David,

I am sorry that I took so long to answer your question, but this Forum does not have much activity and I only monitor it occasionally.

The 2 terminal sending unit is just a switch, so it does not make any differance which wire goes on the short terminal. If you are reading cold all of the time, you probably have an incorrect single terminal sending unit, or the wire is grounded. The single wire unit is made in both 12volt and 6 volt versions. Make sure that you have the correct one. C& G Ford parts has the correct parts for your pickup. They are also very helpful in making sure that you have the correct parts.

Cgfordparts.com/

The Early Ford V-8 Club of America has an adviser for Ford trucks and many of the members have trucks. You will feel right at home there. Here is a link to their website.

http://www.earlyfordv8.org/index.cfm

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