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#1
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Another erratic temp guage - 95 606
Folks, after replacing the engine harness and both two pin temp sensors, the temp guage still acts erratically. Warms up fine, but once at temp will creep up to 120, drop back to 100, and basically jiggle around. It will often settle at below 100 ( bet 100 and 80) once its being driven more than 30 minutes.
Engine does not appear to be overheating at all ( just changed the GPs so had to run engine at idle to warm it a few times) . Question: will a bad ground at temp sensor in dash also cause the fans to turn on? I finally disconnected the new aux fans as they were coming on unneccesarily . Nor can I finish the AC system fix with the fans always on. So temp guage - signal must be fixed before next summer! Every other 606 I've had went to 80 and held like a rock, only rising after coming off a long highway pull. Thank you for any input! ( btw, I did not replace the four pin sensor - maybe I ought have? |
#2
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Test by measuring the actual engine temperature vs. the gauge. A non-contact thermometer from Harbor Freight is about $25 or so and perfect for troubleshooting problems like this.
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Respectfully, /s/ M. Dillon '87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted '95 124.131 (E300) "Sapphire", 380k miles '73 Balboa 20 "Sanctification" Charleston SC |
#3
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test the sensor resistance from the square wiring plug near the glow plug relay, it has the wires from the 2 pin sensor that is near cyl 6, one of the two pins run the gauge, and one goes to the glow plug controller.
The fans kicking on high for no reason (at least for me) was (what I think) a bad solder joint in the pushbutton control unit - as I replaced mine with another part I bought from a jyard.
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2012 BMW X5 (Beef + Granite suspension model) 1995 E300D - The original humming machine (consumed by Flood 2017) 2000 E320 - The evolution (consumed by flood 2017) |
#4
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Zulfiqar,
Do you know the sensor resistance values, or are they published in MB literature?
__________________
Respectfully, /s/ M. Dillon '87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted '95 124.131 (E300) "Sapphire", 380k miles '73 Balboa 20 "Sanctification" Charleston SC |
#5
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Quote:
they are the same values as the pre glow temperature sensor, there are two pins, each pin is a separate sensor referenced to ground of the cylinder head. 20C = 2.5 kohms 30C = 1.7 kohms 40C = 1.1 kohms 50C = 830 ohms 60C = 600 ohms 70C = 435 ohms 80C = 325 ohms 90C = 245 ohms 100C = 185 ohms. so you can deduce from here that your gauge going to 120C shows that your wire is shorting to ground somewhere
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2012 BMW X5 (Beef + Granite suspension model) 1995 E300D - The original humming machine (consumed by Flood 2017) 2000 E320 - The evolution (consumed by flood 2017) |
#6
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Thnx folks, An infrared therm is next step. Z thank you for the info. The GP harness is brand new, ( original harness replaced) which I thought would cure the issue. Then there was the collapsing upper radiator hose. And then both two pin sensors were replaced. Only the four pin remains as factory.
Yet, there is no other evidence of a failed pump or thermostat. I beleive it all electrical. Temps were at over 100 when I got home. Upper hose was warm to touch, intake mani was still near cold! This morning after a five minute run, 120, but the upper rad hose wasn't even fully pressurized and intake still cold! AAAARRGH! Good news is I have until next spring to fix it , replace the condensor and recharge the AC. Given that the wiring harness is brand new, where would the short be? It does trigger the aux fans, which is why the brand new aux fans are now unplugged. This leads me to believe it's not the guage ground itself. These old "simple" diesels are not so simple to diagnose, are they!? Last edited by WINGAS; 09-15-2015 at 07:00 AM. |
#7
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Quote:
If you remove the crossover pipe you will see a small wiring loom going from the main to the driver side of the car to a small square plug, that plug is where the temperature sensor for the gauge, the preglow and the 2 wire sensor at the very front of the cylinder head patch into the body wiring. The round temperature sensor goes to the ELR and EGR control units behind the battery - bundled in the main engine wiring harness. btw - the upper radiator hose collapsing is not anything to be alarmed of, its also proof that the system is airtight, the expansion tank cap requires some amount of negative pressure to open its relief valve. This can cause the hose to collapse. It did that on mine too, no problems at all.
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2012 BMW X5 (Beef + Granite suspension model) 1995 E300D - The original humming machine (consumed by Flood 2017) 2000 E320 - The evolution (consumed by flood 2017) |
#8
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Thank you Zul. I havent chased it down yet, as I know its not overheating. Odd thing is after some runtime, like 2 hours, the guage seems to settle in and work fine. 6 hours of runtime yesterday and it was reading fine for the final 4. ?
Changing the upper rad hose did nothing so... quite right! |
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