The Age Old Temp Sender Dilemma - HELP PLEASE?

[Larry M.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Don,

You might find an NOS GM

Make certain that NOS is Made in USA versus later ones that were made in Mexico. I heard from reliable sources that when production went south of the border, gage calibration issues became much more frequent and greater error.

Probably best check is in boiling water (212 F) with a ohm reading of 78 ohms +/- 2.

Larry

[Gary B.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

I just searched eBay and I found no examples of GM 6490453 that appear to me to be authentic GM NOS items.

Gary

[Larry M.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Some interesting reading I discovered while doing research for this thread. Well worth the read.

https://www.corvetteforum.com/forums...e-success.html

Larry

[Mark E.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

I'm repeating, but the unit from NAPA for $9 has worked well for me. And if there is an issue, they're not difficult to swap out.

[Ed D.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

I purchased a Electric Limited unit with the GM part number on the box. I fooled with it for over a year on my 72 sb. I could not get the temp needle to move very far off the base line. I found the original sending unit in my parts bin while looking for an other part and decided to re install it to see how it would react. I measured the impedance of the unit before I installed it it was approx 950 ohms. The original indicated properly, the needle showing 180 F, the second meter line. When I removed the E L unit (06490453) the impedance was 1500 ohms. Changing the unit is a bit of an annoyance as it leaks anti freeze when the temp unit is removed. This is just my experience and may give you some directions.
Ed

[Gary B.]

[Bill S.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Anybody remember the thread from a few years back a member had done a lot of research and ohm testing on all of the available temp sensors. I thought I subscribed to it but i guess I didn't. tried to search and came up empty. Hopefully someone will remember a post a link to the thread.

[Richard M.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Bill that was me. I'll find the link.

https://www.forums.ncrs.org/showthre...rature-Senders

Caveat... It was for the C1 cars with a different connector configuration.

Note that even my high priced GM NOS sender was not any better than the others that failed my tests.

Summary: The NAPA part was found to be the best choice.

Rich

[Mark E.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Summary: The NAPA part was found to be the best choice.

Rich

As I was trying to tell you guys...

[Jim L.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Bill that was me. I'll find the link.

https://www.forums.ncrs.org/showthre...rature-Senders

Caveat... It was for the C1 cars with a different connector configuration.

Note that even my high priced GM NOS sender was not any better than the others that failed my tests.

Summary: The NAPA part was found to be the best choice.

Rich

Two NAPA senders I tested in my '60 exhibited the thermal run away issue about which I've written on CF.

Note that the resistance vs temp curve was fine. That's not the problem.

The problem is that the resistance begins to spontaneously decrease as the current through the sender warms the internal thermistor. As the resistance decreases, the current increases which causes the resistance to decrease more..... Rinse and repeat.

This, of course, isn't the issue here regarding gauges reading too LOW. However, it is what has been my experience with the NAPA senders.

[Richard M.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Two NAPA senders I tested in my '60 exhibited the thermal run away issue about which I've written on CF.

Note that the resistance vs temp curve was fine. That's not the problem.

The problem is that the resistance begins to spontaneously decrease as the current through the sender warms the internal thermistor. As the resistance decreases, the current increases which causes the resistance to decrease more..... Rinse and repeat.

This, of course, isn't the issue here regarding gauges reading too LOW. However, it is what has been my experience with the NAPA senders.

Jim, Yes your analysis was very informative. I still don't understand why the manufacturers do not provide a fully tested part, at temperature. The failure rate would be astronomical. Instead, we test them for them.

I tested 2 Napa differently part numbered senders.

The Napa Echlin TS6469 had published specs. This is the one that proved to be most accurate.

The Pro Former TS6469SB does not show specs and failed my tests.

Rich

[Bill S.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Bill that was me. I'll find the link.

Rich Thank you for finding the link. Also it is a great thread with a lot of info.

[Don L.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Thanks to all for helping me through this project. It's something that's been nagging me for too long, and after watching the temp gauge climb during an Independence Day parade and not knowing what the temp actually was, I decided to fix it once and for all.

I bought a sender from Full Throttle Corvette, which I'm told is actually a Lectric Limited sender. I had a sender that I bought from Paragon in the engine and I bought a used sender from David Sokolowski too. I conducted a study at a few different temperatures and here's what I found:

Temp Sender Data.jpg


Temperatures in this matrix are approximate. It's unbelievable how fast the senders lost temp once I took them out of the hot water.
Seeing that the used OE sender closely matched resistance figures I found on this forum and others, I decided I'd go with the OE (wasn't really ever a doubt).

I also changed out my thermostat, since I had the coolant drained down.

I'm happy to report that the used OE gives me a gauge reading exactly as I expect. See photo of my gauge, taken while driving on a 90*+ day. Of course the needle climbed somewhat when idling and the needle climbed more substantially when I shut the car down for ten minutes then turn the key to the ON position to get a reading. In fact, the needle climbed to approximately 210* through heat soak once shut down.


Thanks again to all for the advice. I now have confidence in my gauge. I no longer need to make mental adjustments to the gauge reading. It's been a long time coming.

[Bill S.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

It has always bugged me how people that make a reproduction part make it wrong. If you go through the process of making the part why not make sure it is 100% correct. In this case the why not specify the Ohm readings that correspond to what GM had back in the day?