Temperature Gauge sender test values? - Mercedes-Benz Forum
 
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post #1 of 10 (permalink) Old 07-22-2019, 07:04 PM Thread Starter
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Temperature Gauge sender test values?

Does anyone happen to know what the single pin sensor that feeds the temp gauge inside is supposed to read in terms of Ohms? I'm sure there's a table for it somewhere, but I can't find it.

Been chasing my tail with a running hot issue and just realized (after replacing the thermostat, fan clutch, and radiator) that I never confirmed that the temp gauge was reading correct.... not my proudest moment of realization...

As usual, all help is appreciated
-thanks
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post #2 of 10 (permalink) Old 07-22-2019, 09:23 PM
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Try section 54-261 in the manual. My computer won't let me make a copy of it for some reason.

Oops, sorry. Thought you were asking about the outside temp gauge in the cluster.

Last edited by luckymike; 07-23-2019 at 08:56 AM. Reason: misunderstanding
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post #3 of 10 (permalink) Old 07-23-2019, 04:01 AM
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Quote:
Originally Posted by dude99 View Post
Does anyone happen to know what the single pin sensor that feeds the temp gauge inside is supposed to read in terms of Ohms? I'm sure there's a table for it somewhere, but I can't find it.

Been chasing my tail with a running hot issue and just realized (after replacing the thermostat, fan clutch, and radiator) that I never confirmed that the temp gauge was reading correct.... not my proudest moment of realization...

As usual, all help is appreciated
-thanks
Hey dude,

I could not find a temp/resistance chart for you but maybe this will help some I hope..

A couple of years ago I chased a high reading temperature gauge reading on my '91 500SEC Euro. I changed many parts due to various reasons and in the midst of all I measured the ohms readings of that sensor (x2) at both room temperature and with totally warmed up engines.

"Today, I finally got some time alone with two cold Mercedes & my wife's car to travel between them... to swap gauge temp sensors & do some measurements...

560SEC COLD - 500SEC COLD *measured at 65F ambient
-----------------------------------------------
654 Ohm - 872 Ohm

560SEC HOT - 500SEC HOT

050 Ohm - 040 Ohm
(85C Gauge) - (100C Gauge) Temp Gauge Readings


I swapped the temp sensors from 560 to the 500 in question here and when the motor warmed the 500 gauge read 105C to 110C... In addition, using an IR temp gun, the 500 thermostat housing indicated 205 - 210F .... 195F at the top hose outlet...

With those numbers in mind, I'd surmise the 100C gauge reading is pretty much accurate...

I checked at the MB dealership yesterday, by VIN, about the temp sensor.. Both models use the very same part.. 87 US 560SEC and German version '91 500SEC....
"


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post #4 of 10 (permalink) Old 07-23-2019, 05:27 AM
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Pull the sender out of the engine. Run a jumper from the case of the sender to an engine ground. Immerse the tip of the sender in a tin can of water. Boil the water with a propane torch and see what the gauge says. (Should be 100C)
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post #5 of 10 (permalink) Old 07-24-2019, 03:14 PM Thread Starter
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Hey dude,

I could not find a temp/resistance chart for you but maybe this will help some I hope..

A couple of years ago I chased a high reading temperature gauge reading on my '91 500SEC Euro. I changed many parts due to various reasons and in the midst of all I measured the ohms readings of that sensor (x2) at both room temperature and with totally warmed up engines.

"Today, I finally got some time alone with two cold Mercedes & my wife's car to travel between them... to swap gauge temp sensors & do some measurements...

560SEC COLD - 500SEC COLD *measured at 65F ambient
-----------------------------------------------
654 Ohm - 872 Ohm

560SEC HOT - 500SEC HOT

050 Ohm - 040 Ohm
(85C Gauge) - (100C Gauge) Temp Gauge Readings


I swapped the temp sensors from 560 to the 500 in question here and when the motor warmed the 500 gauge read 105C to 110C... In addition, using an IR temp gun, the 500 thermostat housing indicated 205 - 210F .... 195F at the top hose outlet...

With those numbers in mind, I'd surmise the 100C gauge reading is pretty much accurate...

I checked at the MB dealership yesterday, by VIN, about the temp sensor.. Both models use the very same part.. 87 US 560SEC and German version '91 500SEC....
"
I actually just got through reading your thread. I'm thinking I may be heading to the same solution as you with the 79*C T-stat. I think my current new one is opening late, I have a new one under warrantee coming but we'll see what happens.

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Originally Posted by John350
Pull the sender out of the engine. Run a jumper from the case of the sender to an engine ground. Immerse the tip of the sender in a tin can of water. Boil the water with a propane torch and see what the gauge says. (Should be 100C)
This is a great idea, I'll see about rigging this up over the weekend.

Thanks all!
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post #6 of 10 (permalink) Old 07-24-2019, 04:48 PM
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This is a great idea, I'll see about rigging this up over the weekend.
Vancouver covers a lot of altitude. If you're looking for an exact answer, you may have to take that into consideration. At 1500m you're down to about 95C.
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post #7 of 10 (permalink) Old 07-24-2019, 04:53 PM Thread Starter
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Valid point... I'll check my altitude and compensate accordingly
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post #8 of 10 (permalink) Old 07-25-2019, 02:22 AM
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Vancouver [in round numbers] is sea level.


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91 500SEC EURO Germany
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post #9 of 10 (permalink) Old 07-25-2019, 06:59 AM
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Vancouver [in round numbers] is sea level.
Except for the mountains... There are ski areas practically within walking distance of down town.
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post #10 of 10 (permalink) Old 07-27-2019, 09:20 AM Thread Starter
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The burbs are also above sea level
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