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Coolant Temp Sensor
I have a question about the coolant temp sensors on my 81 300D. I noticed that there are two of them, one above the thermostat and another between the 2 & 3 cylinders glow plugs. Which one is for the gauge on the dash?
I noticed on the wiring diagram for the glow plug system that there is a temperature sensor for the glow plug system. Could the one between the glow plugs be for that purpose?
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1981 Mercedes 300D |
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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. |
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I thought that the aux fan was controlled by the HVAC system, and that it only came on when the A/C compressor is running, to blow air across the condenser?
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1981 Mercedes 300D |
#4
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Quote:
That's not exactly how it works, even when it does work that way.
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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. |
#5
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The aux fan has only ever come on when I'm running AC. To Tango's point, I'm sure the mechanism is very similar across all model years, though mechanical parts would be updated as needed over time.
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Never be ashamed to ask for help. 1985 300D 1987 300SDL 1970 Jaguar E-Type OTS 2002 Dodge Intrepid (Traded In) 2011 Ford Crown Victoria |
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I am sure that they are not. 100% sure.
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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. |
#7
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Looking at the wiring diagram for my 81 300D, it appears that the aux fan for the condenser is controlled (via a relay) by the temperature switch on the receiver dryer. So that throws the idea of the temperature sensor on the t-stat controlling the aux fan out.
I wish my wiring diagram would show the location of the coolant temp sensor for the gauge. I think i'll just ground the wire of one or the other sending units to see which one moves the gauge, but if one is for the gauge, what is the other one for?
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1981 Mercedes 300D |
#8
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Quote:
Just keep you fingers out of the aux fan when you ground the switch in the thermostat housing!!!
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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. Last edited by tangofox007; 04-25-2012 at 04:04 PM. |
#9
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Temp sending unit is in the head. The one in the T-stat housing is a cold eng lockout switch. It restricts blower operation in the heat position until eng reaches 33 deg
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82 300SD 202K 82 300SD 233K 83 300TD 340K 82 300TD 98k euro (parts on the hoof) 85 300TD 282K 83 300TD 197K Last edited by Johnt49; 04-25-2012 at 06:42 PM. |
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I'm not going to give you the satisfaction and argue with you. Just know that the way you relate to people in general on here isn't appreciated. And I'm 100% sure about that.
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Never be ashamed to ask for help. 1985 300D 1987 300SDL 1970 Jaguar E-Type OTS 2002 Dodge Intrepid (Traded In) 2011 Ford Crown Victoria |
#11
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And you almost had me convinced that all MB models are the same.
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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. |
#12
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I looked at the EPC and that looks correct.
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Thank you all for your assistance. I put the wire from the sending unit on the side of the head between the glow plugs, to ground and sure enough the gauge was pegged. So that part of the mystery is solved.
So the other one is the cold engine lock out switch, that restricts blower operation when cold? I see that on my airflow diagram that I have here. Part two is solved. Thank you all for helping me satisfy my curiosity. Now I know what sensor does what, and why. One last question... What is this "EPC" that was mentioned by gatorblue92?
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1981 Mercedes 300D |
#14
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EPC = electronic parts catalog. Look for the thread "done the right thing" and it'll point you to MB's online catalog with blow-up drawings.
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#15
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Ah, I see. So I have been using the "EPC" wiring diagrams all along, without knowing it. Thanks again for your help.
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1981 Mercedes 300D |
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