ClassicCar

hudson8

How come the heat sensor which screws into the head of a 52 eight cylinder will not register correctly? I have 2 N.O.S. ones that fit perfectly but will peg the hot side of the gauge as soon as the engine begins to warm up. Perhaps the 2 N.O.S. ones were originally for a 12 volt system which would influence the ohms resistance , or am I all wet in this thinking? Your thoughts please. Thanks---Cliff Minard.

WildWasp

hudson8 wrote:

How come the heat sensor which screws into the head of a 52 eight cylinder will not register correctly? I have 2 N.O.S. ones that fit perfectly but will peg the hot side of the gauge as soon as the engine begins to warm up. Perhaps the 2 N.O.S. ones were originally for a 12 volt system which would influence the ohms resistance , or am I all wet in this thinking? Your thoughts please. Thanks---Cliff Minard.

The following link is to a bulletin provided by Alex Burr and located on Ken Cates Stepdown site. You will find the number of the sender used for the years listed. In addition to the sender information the bulletin notes that voltage regulators were used for some models. The point... is you volts regulator operation normally?

http://hudsonrestoration1948-54.com/PDFFiles/FUEL%20AND%20TEMPERATURE%20DASH%20UNITS.pdf

Jon B

The two thoughts that occur, are:

1) was the gauge itself working, before? Possibly the problem could lie there.

2). It's possible (but highly unlikely) that both NOS sensors were bad. Sometimes antique parts vendors obtain the stock of a parts company, that may include NOS items that had been returned by the customers because they were defective, but those items somehow made it back onto the shelves.

3). I'm a bit hazy on things electrical, but if you hooked this thing up to an ohm meter, took a reading, then submerged the sensor in a pan of boiling water, wouldn't you see the reading gradually change? If so, at least you'd know that it was working correctly?

53jetman

hudson8 wrote:

How come the heat sensor which screws into the head of a 52 eight cylinder will not register correctly? I have 2 N.O.S. ones that fit perfectly but will peg the hot side of the gauge as soon as the engine begins to warm up. Perhaps the 2 N.O.S. ones were originally for a 12 volt system which would influence the ohms resistance , or am I all wet in this thinking? Your thoughts please. Thanks---Cliff Minard.

Cliff - I don't beleive the heat sensors are voltage particular, as the units that we all use now for the six cylinder engines also are used in some Chrysler & Ford engines with 12 volt electrical systems. I know the one in my Jet was also recommended for the Ford & Comet small six cylinder engine (which were both 12 vot electricals)

Jerry

53jetman

Richard E.

I do know that the 6v heat sensors sold at obsolete Ford parts places fit in the Hudson but they do not work, something to do with ohms??? I am not good at auto electrics. You have to find a good Hudson one!

SuperDave

Just remember not to use any teflon tape on the threads.

hudson8

SuperDave wrote:

Just remember not to use any teflon tape on the threads.

First off I would like to thank everyone for taking the time to answer my post. Dave, how would teflon tape influence the reading on my temperature gauge since that is what I used on both of the N.O.S. ones? Thanks again.---Cliff Minard

SuperDave

hudson8 wrote:

First off I would like to thank everyone for taking the time to answer my post. Dave, how would teflon tape influence the reading on my temperature gauge since that is what I used on both of the N.O.S. ones? Thanks again.---Cliff Minard

There is only one wire attached to the sensor. The flow of current from the wire through the variable resistance of the sensor to ground is what the guage is reading. If the sensor has a poor ground, it won't read correctly. In other words, you have placed another resistance in series with the sensor. If you used enough tape, you could prevent the guage from working all together. Most likely, there are some metal to metal contact somewhere..if you are lucky.:o

Uncle Josh

Well, for about $20, you could get a mechanical gage from Auto Zone etc and take all the electrical questions out of the mix just to check it

Hudson308

Just to answer the 6V vs. 12V question... you DO need to reduce the voltage supplying the stock gauge and sender when converting to 12 volts. If there are sender P/N's that work for both voltages in two different applications, the respective gauges would have different internal coil resistance to make up the difference. Otherwise, twice the voltage with the same coil resistance would equal twice as much current. The gauge would then run hot and/or burn out. Getting back to your problem... maybe the teflon tape is affecting your reading. If the sender resistance goes up with temperature, the tape would add series resistance as previously stated. You would expect it to read high all the time, though... not just as it warms up.

Heart Of Texas

SuperDave wrote:

There is only one wire attached to the sensor. The flow of current from the wire through the variable resistance of the sensor to ground is what the gauge is reading. If the sensor has a poor ground, it won't read correctly. In other words, you have placed another resistance in series with the sensor. If you used enough tape, you could prevent the gauge from working all together. Most likely, there are some metal to metal contact somewhere..if you are lucky.:o

Exactly... this information coupled with the Hudson Bulletin posted earlier by WILD WASP will provide you with the information needed to ID the correct sensor and voltage regulator needed to make you gauge operate correctly. The gauge in your car uses a voltage regulator to create a constant 5 Volts DC to one side of the gauge. As the heat sensor heats up the resistance to ground changes creating a changing resistance against a constant voltage which is read across the gauge. The outcome is a gauge that reads from cold to hot as the engine heats up.

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