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| Overheating: coolant or electrical? https://slantsix.org/forum/viewtopic.php?t=56238 |
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| Author: | WyoCowboy [ Tue Sep 23, 2014 1:55 pm ] |
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Ok, I got the TS6178 from NAPA, and also the pigtail connector 784827 as suggested. However, the problem is that the female connector is too small diameter, or the post from the sender is too large diameter. Point is, they don't fit. I am able, however, to slide the existing button top terminal onto the push on terminal post, and it does stay. So I am getting connectivity and a reading. Now my readings are interesting. Now the needle goes over towards the high mark, but just under. Not as far as before. If I drive down a long hill, then the needle swings back over to midway, right about 12 o'clock. This never occurred with the previous temp sender. While idling, the meat thermo still reads 180 in the radiator. This new sender is much more sensitive to temp swings, but in my opinion is still reading too high at normal operating temp. Shouldn't the needle be about halfway in the gauge? I'm also wondering if the temp sender isn't far enough into the block, as I didn't want to tighten down the size reducer too much because it was getting really tight. And the probe just peaks out of the bushing. Maybe I'm getting too much block/metal temperature and not enough coolant temperature? Any other ideas or suggestions appreciated. |
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| Author: | nm9stheham [ Tue Sep 23, 2014 2:54 pm ] |
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Here is a bit of info that might be of some comparative interest and might give you some options: I've been interested in this topic because my temp sensor has gone out too. Got an Echlin TS6626 (which is a cross from the Standards Brand TS52 which is called for for my '62 Dart /6) and has a button top and 1/4" NPT threads. Installed it and got pretty much the same results as you. At cruise under mild load and in a long 6-7% grade climb at 50 mph so that the 180F t'stat should be pretty well open (and with ambient air temp at 60F, dry), the guage reads at the 4th of 5 divisions in the normal range. So, like yours, it reads a bit higher than I would expect. This sensor's spec on the NAPA site is 125 ohms at 125F and 17.1 ohms at 200 F. I checked this sensor's resistances and found it to be 80 ohms at 125F (hot tap water and a candy thermometer), and about 30 ohms with the engine coolant at 175 F in the top tank of the rad at idle (meat thermometer). If you can read your TS6178 temp sensor's resistance (from connection to sensor case with the guage wire disconnected) when at idle and at 180F, you sould be able to compare the 2 units' resistances to see if one has a higher resistance (which will give a lower guage reading). BTW, if I go from the Standard Brands eCatalog part listing for your car, TS 18, and cross it to the Echlin PN, it comes up Echlin TS6707, which has the 1/8"x27 NPT thread Like the TS6178 and with the button top connection. The resistance spec is nominally 129 ohms at 100F and 12 ohms at 250F. Your present sensor is listed to be 15-19 ohms at 220 F per NAPA (as Dan cited before); how to relate the 2 at the same temp is hard to do since the resitance vs. temp changes are not linear. But the TS6707 might be worth a shot to see if it gives you a more mid-range reading. Or just try another TS6178; there are variations from unit to unit, and you might get another one that is a bit higher resistance. BTW#2, I would think that the head's casting metal around that area would be pretty darned close in temp to the coolant temp in that area, assuming the coolant passages are reasonably clean. And you might want to crimp a ring lug on your temp sensor wire and use a couple of small nuts and a lock washer for the connection to the TS6178 if that works best for you. Hope this helps. (Tried to post a guage pix, but can't figure that out on this this site.) |
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| Author: | WyoCowboy [ Tue Sep 23, 2014 3:25 pm ] |
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Thanks for your suggestions. I may just live with it for awhile. Anyhow, here are instructions for posting photos: http://www.slantsix.org/forum/viewtopic.php?t=4434 |
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| Author: | emsvitil [ Tue Sep 23, 2014 3:49 pm ] |
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The NTC resistors used in temperature probes will give you an almost linear curve if you use the log10 of the resistance. Make an excel spreadsheet chart with X axis as temp and Y axis as Log10 of the resistance. You can then interpolate and compare the different specs. |
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| Author: | nm9stheham [ Tue Sep 23, 2014 4:46 pm ] |
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That is interesting....I'll try that from the data I have and see how well it matches; I just ahve a couple of data points though. I may also try some different sensors in my car. |
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| Author: | emsvitil [ Tue Sep 23, 2014 4:50 pm ] |
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http://www.maximintegrated.com/en/app-n ... mvp/id/817 |
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| Author: | nm9stheham [ Tue Sep 23, 2014 7:19 pm ] |
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Tables done... will post info tomorrow. My son just got back from Boston so hearing the stories. |
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| Author: | nm9stheham [ Wed Sep 24, 2014 9:53 am ] |
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FWIW.... I worked up an Excel spreadsheet on these sensors using a smiplified, single logR vs temp coefficient characteristic, and the first thing that popped out was that the temp vs logR coefficient was pretty consistent amongst the data points from the few specs. There weren't a LOT of data points, but the coefficients came out with a spread of <20% so that was encouraging. Working out the predicted NOMINAL resistances at 180F: TS6178 = 44 ohms TS6707 = 63 ohms TS6626 = 29 ohms (I measured 30 at 175F) ON the TS6178 that the OP is now using, the resistance spec at 220F varies from 15 to 19 ohms. Predicting back to 180F gives a resistance range from 39 to 49 ohms. So a unit to unit variation could move the guage needle a fair amount. Measuring the actual sensor resistance at 180F as before might give the OP an idea if he has a sensor resistance on the low (hot reading) end of unit tolerance or the high (cold reading) end. And it looks like my guage would read a bit below mid range at 180F If I also swapped to the TS6178. Another thing to try now! I have been wondering now if there is any calibration on the guages themselves. Someone on the forabodiesonly forum last spring went through a lot of gyrations on fuel guages, and finally found a couple of small adjustments in the guage itself to use to cal in the fuel sender. So I wonder if there is something similar on the older temp guages. |
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| Author: | SlantSixDan [ Wed Sep 24, 2014 10:41 am ] |
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Keep in mind also that the gauge itself can drift from its original calibrated response to the varying levels of resistance from the sender -- especially if the engine has overheated, the sender wire has become grounded, or the gauge has elsewise been pegged. You may see different results after replacing the gauge itself. |
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| Author: | nm9stheham [ Sat Sep 27, 2014 9:33 am ] |
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Justr an update for info: I switched out the TS6626 sensor for the TS6187 sensor (the NAPA cross from the TS17) and the guage reads 1 division cooler under the same drive test conditions. The measured resistance at 175 degrees (coolant in top tank of rad) is 39 ohms; was 30 ohms with the TS6626. Tnx to emsvitil for the info on the sensors, and all the other info shared by others! |
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