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Gemmer

Temperature transmitter

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Looking for an original engine temperature transmitter for a positive ground E1 engine. 

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Doesn't matter which way current flows in the temp sender. A later negative ground sender will work on a positive ground truck just like a sandwich will taste the same if you turn it upside down.

 

 

If the 320 are like the later trucks the temperature and gas gauges are powered from a common source. So if your gas gauge is also not working it's unlikely it's the temp sender that is bad. (just in case) 

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Datsunmike,

The reason I want to get an original temp sensor is I had to replace mine about 10 years ago. At the time the only ones available were for Datsun 510s. They were negative ground. Since that time my temp gauge reads cold when the engine is running at 140 degrees and hot when the engine is dead cold. The original sensor was insulated from the fitting that screwed into the block so it was not grounded.

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The 510's (and most other Datsuns) sender is just a resistance that varies with temperature. Higher resistance when cold and less resistance when hot. A resistance reads the same no mater which way around you place it in a circuit just like a light bulb. The gauge will reverse readings if you swap the wires to it or if the the electrical system is switched from a positive to a negative ground..

 

 

 

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There is only one wire going to the sensor. The latter part of your last sentence “if the electrical system is switched from a positive to a negative ground” seems to correctly describe my issue. 

Note: my PU320 is a positive ground.

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OK, so when the truck is parked in the driveway with no key in the ignition the temp needle on the gauge should be all the way at the top(fully overheated position), is this what happens in your truck?

When you turn the key on and just wait a minute without starting the truck what happens?

It should drop to the bottom, is this what happens in your truck?

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Has anyone successfully gotten a non working temp gauge working again? Is there an aftermarket temp sensor that'll work?

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320 Newb,

There is in fact a sensor available here “www.datsun-roadster-parts.com/product/he-070”

they want $148.80 for it. I don’t have that kind of money for a part that costs $20.00

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4 hours ago, datzenmike said:

The 510's (and most other Datsuns) sender is just a resistance that varies with temperature. Higher resistance when cold and less resistance when hot. A resistance reads the same no mater which way around you place it in a circuit just like a light bulb. The gauge will reverse readings if you swap the wires to it or if the the electrical system is switched from a positive to a negative ground..

 

 

 

 

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Datzenmike,

Just to be perfectly clear, all PU 320 trucks and SPL 310 roadsters came from the factory configured as positive ground vehicles. While some of these have been converted by their owners to negative ground autos, I have kept mine in its original state, positive ground. It has been documented that the sensors work differently. This sensor (sender) is the only one that works with a stock 320 or 310 gauge for the E1 engine. It is not a matter of + or - ground. So what I’m looking for is a thermal transmitter #25250-30100.

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The instead of the resistance lowering at the temp goes up it would have to be low resistance when cold and increasing as it warms up. Definitely different and I'll keep in mind.

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Wayno,

when they ignition is off (no key) the gauge registers hot. Insert the key and turn it on, the gauge still registers hot. When the truck warms up to operating temp, the gauge registers cold.

 

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6 hours ago, Gemmer said:

320 Newb,

There is in fact a sensor available here “www.datsun-roadster-parts.com/product/he-070”

they want $148.80 for it. I don’t have that kind of money for a part that costs $20.00

$149 is bonkers. No thanks. 

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6 hours ago, Gemmer said:

Wayno,

when they ignition is off (no key) the gauge registers hot. Insert the key and turn it on, the gauge still registers hot. When the truck warms up to operating temp, the gauge registers cold.

 

 

If it goes all the way to the cold position when warmed up I would say something is broken, as it should only go half way down(be in the middle).

Until you find what you need at least it works, just backwards, Roadster parts are an option, you could look into MG 1500 engine parts(Triumph 1500 also), they are sort of the same engine, the distributors are the same, I have a positive ground 1963 Datsun 320 with electronic ignition(Crane) from a MG Midget, so maybe a positive ground temp sender will work, I do not have them engines around here anymore to check the temp sender.

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Wayno,

Since the temp gauge I have works albeit backwards, I’ll just keep on truckin until I find an original. It’s just irritating that I have a completely original with this one exception.

i did check MG parts but they were not compatible.

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Do you have a good local sparky you could have take a look? I've got a good local who rebuilt my stock generator for $100 and got my non-working wiper motor cleaned up and working for $20. Some of the best money I've spent.

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Really dont need a sparky, I know what is wrong. Need an original part #2520-30100 Thermal Transmitter for an E1 engine that was manufactured as a positive ground vehicle. 

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The 320 and 1500 temp sender is a mechanical device that is either on or off depending on the bimetallic reeds being open or closed. It has the effect of supplying a higher average voltage across the gauge when it is cold, which is the opposite of the newer types. It has nothing to do with positive or negative ground.  I do not know of any equivalent senders.

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Thank you for the explanation. While I thought it had to do with + versus -.What is at issue is that these were unique to the 320 and 1500 series.

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Probably the 310, 311 and 312 sedans and other positive ground vehicles too ( but I don't know this for sure). It would just be a coincidence that other positive ground vehicles used this approach. Just the technology at the time.

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The thing to keep in mind here is that the Datsun 320 has no aftermarket support and it likely never will, so what is out there is what is left for these trucks.

Maybe there is something that can be made to turn the signal of your sender around, maybe not, maybe something in the gauge itself can be changed, that is for people that understand electricity to figure out.

But since the Datsun 320 and the early Datsun Roadster share a few parts, at least some parts are available as the Datsun Roadster does have some aftermarket support, it may be expensive but at least it is there.

There is also the MG engines/transmissions, they also have aftermarket support and there are a lot more of them out there, there are also the Datsun forklifts, have you tried a forklift shop?

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It's the direction the current flows through the gauge that makes it start at the top or the bottom not the sender. Wire the gauge backwards and the meter will work in reverse.

 

 

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That will not matter. If that were true it would work differently with pos vs neg ground.

I have a used tested sender for $50 or new for $100. Still expensive.

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Well replace the sender with the correct one then. But if you only have the 510 one and it reads backwards switch the gauge wiring. Or switch to negative ground.

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