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Another water temp sender question
https://slantsix.org/forum/viewtopic.php?t=38947		 Page 1 of 1
Author:  redfourjohnd [ Tue Feb 09, 2010 3:41 am ]
Post subject:  Another water temp sender question
Hi everyone,

I just finished refacing and calibrating my gauges in my 68 charger. Voltage limiter is a 5 volt Radio Shack regulator home built version. Put the cluster back in and the water temperature gauge didn't move. New sender in and the gauge goes up to 230 or so, about 3/4 of the gauge. I know it's calibrated right, so the sender ohms must be off, although I haven't checked that yet.

The new sender is the NAPA echlin TS1678. I may have the numbers wrong as I don't have the box in front of me. They asked if it was a gauge or an idiot light.

If the sender is the wrong ohm range for the gauge should I just wire in a resistor? Is there another source for the correct sender? I searched the forum before this post and didn't find the answer.

Thanks!

John D
Author:  SlantSixDan [ Tue Feb 09, 2010 7:04 am ]
Post subject: 
See if it works correctly with a factory-type voltage limiter. The homemade limiter based on a #7805 has a different output than the gauges were designed for (steady 5v instead of pulsed 12v with an average voltage of 5). I think your sender might be a TS-6478, which I believe is the correct one.
Author:  redfourjohnd [ Tue Feb 09, 2010 7:23 am ]
Post subject: 
I bet you're right on the part number Dan.

I bench tested all the gauges with a NOS mopar limiter. They all read low after calibrating to the radio shack limiter. Really low, like 3/4 of the gauge at 10 ohms. I thought that the solid 5 volts would be better than the pulsed 12, and all I would really lose would be the quick warm up of the gauge. Do you think I goofed? I looked at the RTE limiter, but decided to stick with the one I made.

I really don't want to pull the cluster again and recalibrate. It took like an hour each gauge! Bummer for me for sure. :D That's most of the reason I didn't order the RTE limiter.
Author:  SlantSixDan [ Tue Feb 09, 2010 7:38 am ]
Post subject: 
I didn't like the technical disadvantages of the #7805-based limiter, so I never built or used one; I like the "plug and chug" operation of the RTE item.
Author:  redfourjohnd [ Tue Feb 09, 2010 8:17 am ]
Post subject: 
They definitely put a lot of thought into it. The web page they have on it was super informative. I thought long and hard about getting one. Thinking about it again now.

Thanks for your advice!

John D
Author:  KBB_of_TMC [ Tue Feb 09, 2010 9:16 am ]
Post subject: 
Long ago I put a LM7805 into the case of defunct plug-in regulator, with the case used as the heat sink. It worked fine, but took longer for the gauges to come up when you started the car. The RTE is far more sophisticated. I would carefully check the grounding of the LM7805 and dash and its output. If you unplug the temp sender and measure the voltage there, you ought to see 5.0V. If you see more, you probably have a poor ground.
Author:  redfourjohnd [ Tue Feb 09, 2010 1:56 pm ]
Post subject: 
Thanks KBB. I checked the voltage and it's 5.02 volts. I'm pretty sure the regulator is working right.

I called Echlin and the specs for their ts 6178, which is the one I have, are 24.7 ohms at 220f, and 152.2 ohms at 100f. I'm getting 15 ohms at 180f, so this sender is bad apparently. I'll get a new one and keep my fingers crossed.

Usually I go to autozone which is known for junky parts. I went to Napa this time to ensure getting a good part! And I get a bad one. Just my luck, I swear.

Can someone tell me what the ohms should be at a given temperature since we know the range of the sender? I've looked around and can't find the answer. On the gauge from low to middle reading is a difference of 52 ohms. From middle to high the difference is only 13 ohms. As the temp rises the change in ohms is less. Why is that? I'd like to understand if anyone knows.

Thanks again,

John D
Author:  emsvitil [ Tue Feb 09, 2010 4:18 pm ]
Post subject: 
Somebody used a adjustable voltage regulator to get the gauges to read correctly...


Think it came out that you should use 6 volts.........
Author:  redfourjohnd [ Sat Feb 13, 2010 8:46 am ]
Post subject: 
I got a new sender at autozone and all is nearly well now. The gauge reads just 10 degrees cooler than actual now. The needle doesn't get into the "normal" range even. I checked the temp at the thermostat housing with an infrared temperature gun and it was right at 180f.

One thing I learned is that it matters where you check for resistance. I went from the sender to the battery ground and various other grounds and got a lot of different readings.

Thanks everyone,

John D
Author:  64DartVertible [ Tue Mar 30, 2010 1:27 am ]
Post subject: 
Quote:
Somebody used a adjustable voltage regulator to get the gauges to read correctly...


Think it came out that you should use 6 volts.........
I read (probably here) that these gauges were originally designed for the old 6v electric systems and that instead of designing new 12v gauges, they added the mechanical limiter.
That made sense to me, because my 7805-based limiter causes the temp and gas gauges to always read low. A full tank of gas only reads about 3/4 full.
Because of that, and the fact that it takes a while for them to move after starting the car, I ordered one of the RTE units yesterday.
I'm hoping for much better results.
Author:  SlantSixDan [ Tue Mar 30, 2010 6:32 am ]
Post subject: 
Quote:
I read (probably here) that these gauges were originally designed for the old 6v electric systems and that instead of designing new 12v gauges, they added the mechanical limiter.
No, these gauges were not designed for 6-volt service. They were designed to operate on pulsed 12v providing an average of 5v provided by a properly-functioning voltage limiter.
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