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Member
Posts: 26
Location: Wylie, TX | On a 55 Desoto Firedome with stock 291 engine.
Gauge is not indicating temperature, so I followed the repair manual and the gauge sweeps when the wire at the sending unit is grounded. Is it a safe assumption that the sending unit in the manifold is faulty? Just want to double check before I drop the money on a new sender.
Dan |
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Expert 5K+
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Location: Big pimpin' | It would appear so............ |
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Elite Veteran
Posts: 1049
Location: Auckland, New Zealand. | Is there a more scientific way of testing temperature senders, like with an ohm meter in the same way that a fuel gauge sender can be tested? My NOS temp sender is telling my gauge that the engine is hot after driving for 2 miles. When the wire is grounded the gauge needle goes to hot. The engine is running correct at 180 degrees according to an aftermarket accessory gauge and sender. If I buy a new sender, will I just get sent some other sender that fits but is of the wrong heat range as what I have now?
Glenn.
57 Fury. |
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Expert 5K+
Posts: 6203
Location: Big pimpin' | Glenn, I can't stress this enough, when dealing with electrical guages, one CANNOT trust them to be acurate...
I'm running the originalon my '58 Plymouth, and it ALWAYS says it's running hotter than the mechanical guage I have right under the dash.....
Yes, thee is a way to check the resistance..Should be a spec somewhere in the manual, I can't remember it right now.
Chrysler had a problem with the temp guages in the '68-'70 Dodge and Plymouth cars....Wanna know what it was? Guage says running to hot...
Chryslers "Official" TSB fix for the problem? Issue a reprinted guage faceplate that moved the "N O R M A L" range further towards Hot...
Edited by dukeboy 2008-11-22 7:08 PM
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Elite Veteran
Posts: 1049
Location: Auckland, New Zealand. | My temperature gauge on my Fury used to read between cold and halfway. I drove it for 15 years that way. My friends 58 Fury also reads in this range. I don't believe that there is anything wrong with the general temp reading system on these cars at all. They read good. I just have an incorrect sender that's all.
Of course I have looked in the manual and there is no resistance check, I wouldn't have asked otherwise....
Thanks for your suggestions though.... |
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Member
Posts: 26
Location: Wylie, TX | Well I replaced the sending unit in the intake manifold and the gauge is still pegged to left. The car was converted to 12V, and the previous owner told me the voltage was dropped to 6V for all the gauges. I wonder if this gauge was skipped by accident and that is causing it to not function properly? |
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Elite Veteran
Posts: 1049
Location: Auckland, New Zealand. | Well a NOS temp sender came up on Ebay last week so I bought it. It arrived this afternoon, and this evening it is now in my Fury.
Gauge now reads exactly where it should, between 1/4 and 1/3 when warmed up.
So now some scientific proof instead of some educated guesses.
Here's how it went down...
The temp sender that I had in there, purchased brand new from a reputable seller, and resembled the nos one except that it was slightly shorter and all brass. The NOS sender is silver cadmium plated at the exposed part above the manifold.
The temp sender that I had in there, and which was reading way too hot, read the following on my ohm-meter, on the "2000" setting on the meter;
cold = 250 ohms, boiling = 36 ohms.
The correct, original NOS temp sender reads the following;
cold = 680 ohms, boiling = 120 ohms.
Hence the innacurate measurement of the sender that I had in there.
You can count on a NOS part to give you an off-the-showroom-floor reliability...usually...
Problem solved!
Glenn.
 (Temperature sender-NOS-Part 1770-732.JPG)
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 Temperature sender-NOS-Part 1770-732.JPG (20KB - 197 downloads)
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Expert
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Location: NorCal |
NAPA used to have a replacement for the original 1770732 sender, TS6460; their spec is 43-51 ohms at 220°F. |
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Expert
Posts: 2679
| Yep, I went through 2 sending units, one read cold all the time, then the second seems to read right....
it could be too obvious when it reads cold all the time, or hot all the time too....
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Expert 5K+
Posts: 7808
Location: Williams California | OEM Mopar senders nearly always will work perfectly, while there seems to be a lot of discrepancies in aftermarket units. I've had better luck removing old OEM senders from an engine, and finding that they still work perfectly. ---John |
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Extreme Veteran
Posts: 331
Location: Northern North Carolina | Timely info. I was wondering how other folks' temp gauges ran. Now that my 57 is back home (still not running right after the engine rebuild), I remembered that back when it was my daily driver, the gauge always seemed to be a little past halfway, toward hot. No one ever found out why...the car (or the gauge?) was always a little "hot-natured". Now that it's home with a new engine, new radiator, new thermostat, new water pump, new pretty-much-everything-under-the-hood...the temp gauge went 8/10ths of the way to hot, after running about 5 minutes. If I back off the accelerator, the needle drops a bit, but it still past the halfway point on the hot side. I wonder about the temp sending unit (can't remember if it was replaced, though I think so), and will check on that right away.
57PlymouthNC
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1957 Plymouth Belvedere
1956 Pontiac Star Chief
1961 Ford Fairlane |
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Elite Veteran
Posts: 1049
Location: Auckland, New Zealand. | I would suggest, that if you are not sure about what temp the engine is ACTUALLY running at, to either borrow or buy an aftermarket gauge and sender, and run that temporarily. (Very cheap-around $30)
When you have a good average with the accurate equipment, then you can connect up your original gauge again and then troubleshoot that to determine what, if anything, is reading wrong. With mine, it was just the sender which I replaced and now it is reading perfect, with the needle between a quarter and a third once warmed up. Sitting idling in traffic on a hot day will send it up to a half, dropping back down again once moving.
I guess one of those non-contact directional thermometers would do the job too, though that would not be so accurate as it is not actually sitting in the water like the sender is.
Good luck.
Glenn.
57 Fury. |
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Expert
Posts: 1208
Location: SWITZERLAND | A time ago I wanted to replace my Eng Temp Sending Unit (361) and got a longer one, not fitting. Since then I left the Original one. Here on the picture the two Units. The long Unit (on the left) has a Value of 3600Ohm and the Stamp 20, the shorter Original Unit (on the right), just disassembled, has a value of 190Ohm and the Stamp E3 522. For what engine is the is the long Unit? - SERGE -
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Expert
Posts: 3778
Location: NorCal |
At what temperature are the listed resistance readings taken?
The one on the left looks like those used with aftermarket gauges since factory senders seldom use nuts to retain the terminals. |
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Expert
Posts: 1208
Location: SWITZERLAND | 57chizler - 2008-12-22 11:25 PM At what temperature are the listed resistance readings taken? The one on the left looks like those used with aftermarket gauges since factory senders seldom use nuts to retain the terminals. At Room Temperature 20deg. I don't like this nut version, because the contact may go worse and show a wrong temp reading. I just see the sample in the picture of FURY comes out the original package and is a nut version.
Edited by sermey 2008-12-22 5:38 PM
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Engine temp sending unit
