What is the difference between 58-72 and 72-92 Water Temperature Sending Units? (1 Viewer)

[GRM]

I swapped the engine in my 1971 FJ40 and the new engine has the newer temperature sensor installed. I still have not hooked it up.

What is the difference between the two sensors? Do they have the same 25 Ω output? Can the newer sensor be used with the older 1971 cluster?

I appreciate the help.

 

[65swb45]

I’m pretty sure they’re different, and I wouldn’t want to risk shorting out a spendy that’s to find out.

That said, I think I tried it once, over 20 years ago when gauges could still be bought.

It didn’t register.

 

[GRM]

I’m pretty sure they’re different, and I wouldn’t want to risk shorting out a spendy that’s to find out.

That said, I think I tried it once, over 20 years ago when gauges could still be bought.

It didn’t register.

Originally I thought I just wasn't searching hard enough to find the answer. Now that I see that even you don't know, It makes me feel better!

 

[FJ40Jim]

Old thread, but to clarify the senders work opposite each other.
Early sender is Positive Temp Coefficient, meaning as temp rises, resistance in thermistor material also increases.

All later senders are NTC, i.e. increasing temp gives less resistance, more current flow, greater needle deflection. NTC sender is harder to make, but gives more satisfactory gage performance.

 

[GRM]

Thank you @FJ40Jim ! That is exactly what I needed to know.

 

[Dynosoar]

The early sender looks to be a smaller thread diameter too. Maybe it is similar to the 3fe sender?

 

[Dynosoar]

Do you know if the oil pressure sender works differently as well?

 

[GRM]

Do you know if the oil pressure sender works differently as well?

According to the part descriptions, such as this one from cool cruisers of texas, the oil sender is the same for all FJ40, 55, 60, and 62 trucks.

Oil Pressure Sending Units

Oil Pressure Sending Units - Toyota Aftermarket Both Excellent Quality

www.coolcruisers.com

 

[FJ40Jim]

The OPSU works differently. It is described in one of the FSMs. It is not a resistance, it is an on/off connection with the on time (duty cycle) increasing w/ increasing pressure.
FWIW, the E-72 fuel gage & sender uses the same operating principle.

 

[ToyotaMatt]

the Sensor Unions Female Threads are the same

but differ much in height

 

[tlaporte]

So, based on @FJ40Jim’s excellent information a question forms in my mind.

Would pairing a later Temp gauge with the later sender be a potential solution for the OP?

 

[ToyotaMatt]

shorter late model sensor union :

taller Early Model one :