hey, i'm attaching a pic of my thermostat housing. my question is, what is this black plastic unit attached to the top of my housing unit by way of some nut that has a wire coming out of it, running under the aux. water pump, and then getting bundled up with larger wires and running back into the firewall/oblivion???

i'm trying to get a replacement thermostat housing unit off of daw_two and his doesn't have this thing... what's going on here?

it's for my 83 300D turbo. HELP!

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1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)

It's a temp sensor, usually for the aux fan. If you unplug it and jumper the wire to ground with the key on the aux fan should run.

If the replacement does not have it then it is not the correct part.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

does anyone know when the engine came with the sensor, and when it didn't? like, the '81 and '82 didn't have it, but the '83 to '85 did?

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1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)

can you be very specific on this procedure, i'm the most basic of "mechanics" and it's all greek to me.

does that mean that even if it's the wrong part, i can still use it with this re-wiring?

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1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)

No, if you get a housing without it then you will lose the sensor and the protection from overheating it provides. The aux fan is set to run under two conditions. If the coolant temp leaving the block exceeds specs or if the A/C refrigerant pressure exceeds specs. There is a second sensor in the A/C system for that. Removing this sensor will make you lose that one type of protection.

To test the aux fan, pull the black plug off of the sensor pin, stick a nail in the plug to touch the metal contact and touch the other end of the nail to the t-stat housing and with key on the aux fan will run. That sensor is simply an on-off switch which connects to ground when the temperature of the water exceeds a certain threshold (around 100C I think).

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

thanks so much for the quick and concise info!

looks like i'm out a replacement t-stat housing, unless daw's got another one....

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1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)

My '82 has that same set up. IIRC, it is used to keep the HVAC blower from coming on until the coolant reaches a certain tempurature.

NHDOC, the Aux fan does not come on according to freon pressure, it is freon tempurature.

Either way, you do need to replace it with the like part.

Why are you replacing the t-stat housing?

While you are in there, replace the bypass hose as well. Its a 41mm inner diameter as I recall.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

on mine without it no glow.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

T-Stat housing is being replaced because it's got a chip missing on the lip of one of the hoses: http://www.peachparts.com/shopforum/showthread.php?t=257036

this chip is the last remaining leak in my coolant system.

Bypass hose was replaced already, along with ALL of the rubber hoses in the whole system: http://www.peachparts.com/shopforum/showthread.php?t=254989

thanks everyone for the help!

and it DOES look like daw's got some more to choose from....

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1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)

Did you ever try using RTV or another sealing agent instead of replacing the entire housing? I would bet you could get a perfect seal with it unless it was more than a "chip".

You could also fill the chip with JB Weld and file it smooth. If the hose is on it that would probably stay fine too.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

didn't do the RTV thing as 1) everyone seemed to think it would make things worse in the long run and 2) i finally got a good seal on the leak near the firewall without it and discovered this tiny chip on the other leak.

based on the info and opinions, i'm not sure if i'm going to use ANY kind of sealant or chemical to fix this. plus daw_two is offering the part, cleaned up, for a great price. can't beat the real thing!

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1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)

That temp sensor is indeed for the HVAC Blower. It is so that when the outside temps are very low, the blower doesn't blow ice cold air into the cabin and freeze out the passengers.


The the aux fan switch indeed is operated by temperature. Sometimes engine compartment can get very hot which makes the switch kicks in even though the a/c is not working.


Sometimes the housing comes with a bolt plug in the hole, just remove it and you can use the switch from your original housing. But, If daw can't get you one, I think I have a good one from my spare motor.



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1983 123.133 California
- GreaseCar Veg System