1983 240D auxiliary fan temp switch wiring - PeachParts Mercedes-Benz Forum

ASteele · #1 03-25-2020, 04:32 PM

Hello fello Mercedes entrepreneurs, this is my first post on peach parts and I was wondering if there is any way to wire up the auxiliary cooling fan on the front of the AC Condenser to work off of a thermo switch on the thermostat housing? However with that said I want to also have the thermo switch for the Air Conditioning on the Reciever/Dryer still trigger the Auxiliary Fan because I plan to fix the AC during the summer. My thermostat housing has the knockout for a thermo sensor to the auxiliary fan already. But is it possible to have both switches trigger the fan or just one? I have also seen other W123's have a thermo switch on the thermostat housing to trigger the aux fan like the 300TD wagons. Any thoughts appreciated!

Here's a pic of the thermo switch that can screw into the thermostat housing:

And a pic of the thermostat housing knock out:

Usaguy · #2 03-25-2020, 04:47 PM

Why would you want to complicate and replace a fan that just turns constantly on a 240D? (240D doesn't use a viscous clutch or a magnetic clutch it just runs all the time from the water pump pulley)

ASteele · #3 03-26-2020, 01:05 AM

I dont want to replace the engine driven fan on the waterpump at all. I want to make the auxiliary cooling fan kick in when the engine is over heating as a failsafe. Not just kick in when the AC is on.

123boy · #4 03-26-2020, 08:18 AM

Why is your engine "overheating"?

ASteele · #5 03-26-2020, 02:13 PM

My engine is not over heating its just i want to fix whats there. I just recently found out the 1983 240D has a thermo switch on the engine somewhere to trigger the fan in the event of overheating. I want to fix this circuit as to help prevent overheating if it ever happened

Mxfrank · #6 03-26-2020, 04:43 PM

There should be a series of 22mm bungs in the water jacket on the left side of the head. If your engine has a spare, simply remove the plug and install a fan switch from a VW or Porsche and wire it in parallel with the fan switch on your receiver drier. This is the hottest part of the cooling system, so you probably want to go with a 92C switch.

https://www.pelicanparts.com/More_Info/823959481FINT.htm?pn=823-959-481-F-INT&bt=Y&fs=0&SVSVSI=2100

ASteele · #7 03-27-2020, 06:32 AM

Quote:

Originally Posted by Mxfrank

There should be a series of 22mm bungs in the water jacket on the left side of the head. If your engine has a spare, simply remove the plug and install a fan switch from a VW or Porsche and wire it in parallel with the fan switch on your receiver drier. This is the hottest part of the cooling system, so you probably want to go with a 92C switch.

https://www.pelicanparts.com/More_Info/823959481FINT.htm?pn=823-959-481-F-INT&bt=Y&fs=0&SVSVSI=2100

Hey thanks for the info, I was talking with whunter the other day informing him I don't have a sensor in the cylinder head. And he was giving me recommendations. I have the temp sender unit in the middle of the head and two plugs on the left and right of it. I have a spare engine with the cylinder head sensor that I can transfer over if it works still. But how do you wire it parallel with the A/C Drier fan switch? I also need a new auxiliary fan because mine is shot and has no continuity and wouldn't run with a 12v lawn tractor battery attached to it

Mxfrank · #8 03-27-2020, 08:07 AM

Take two wires, attach them to the poles of the new sensor with a couple of crimp terminals. Run them over to the drier, and attach them to the two poles of the pressure switch with piggyback connectors and crimps. You can bundle them in electrical tape for a neater look. Done.

If you want to use an original style, single terminal switch, be aware that the case is the second "contact", since it's grounded to the block. You would have to figure out which of the two leads on the pressure switch is ground, and which is "hot". Then you would run a single wire between the terminal on the new switch and the hot side of the pressure switch.

If you have an old part, you're going to have to figure out exactly what it is, because they aren't all the same. It could be a sensor, which drives a gauge, and would be useless for this application. Or it could be a thermoswitch. If it's a thermoswitch, the temperature set point is important. It may be an 85C switch for the fan, or it could be a cooler switch for the glow plug system. Just because something looks like a fan switch, doesn't mean it will work for your application.

Can't help with the fan.

ASteele · #9 03-27-2020, 11:45 PM

Quote:

Originally Posted by Mxfrank

Take two wires, attach them to the poles of the new sensor with a couple of crimp terminals. Run them over to the drier, and attach them to the two poles of the pressure switch with piggyback connectors and crimps. You can bundle them in electrical tape for a neater look. Done.

If you want to use an original style, single terminal switch, be aware that the case is the second "contact", since it's grounded to the block. You would have to figure out which of the two leads on the pressure switch is ground, and which is "hot". Then you would run a single wire between the terminal on the new switch and the hot side of the pressure switch.

If you have an old part, you're going to have to figure out exactly what it is, because they aren't all the same. It could be a sensor, which drives a gauge, and would be useless for this application. Or it could be a thermoswitch. If it's a thermoswitch, the temperature set point is important. It may be an 85C switch for the fan, or it could be a cooler switch for the glow plug system. Just because something looks like a fan switch, doesn't mean it will work for your application.

Can't help with the fan.

I'll take pictures and upload them to help shed light on the situation

ASteele · #10 03-28-2020, 02:25 AM

Quote:

Originally Posted by Mxfrank

Take two wires, attach them to the poles of the new sensor with a couple of crimp terminals. Run them over to the drier, and attach them to the two poles of the pressure switch with piggyback connectors and crimps. You can bundle them in electrical tape for a neater look. Done.

If you want to use an original style, single terminal switch, be aware that the case is the second "contact", since it's grounded to the block. You would have to figure out which of the two leads on the pressure switch is ground, and which is "hot". Then you would run a single wire between the terminal on the new switch and the hot side of the pressure switch.

If you have an old part, you're going to have to figure out exactly what it is, because they aren't all the same. It could be a sensor, which drives a gauge, and would be useless for this application. Or it could be a thermoswitch. If it's a thermoswitch, the temperature set point is important. It may be an 85C switch for the fan, or it could be a cooler switch for the glow plug system. Just because something looks like a fan switch, doesn't mean it will work for your application.

Can't help with the fan.

So camera is acting finicky so ill use some already existing om616 engine bay pics online to help. My engine only has the engine temp sender unit on the drivers side of the cylinder head and the two Allen plugs to the left and right of the temp sender (temp sender unit is in the middle.) So i would remove the front plug and place the new thermo-switch for the fan in there correct?
In the picture shown below you can see the two plugs in the head and make out the temp sender unit wire in the middle, once again sorry for not being able to take my own pictures, but you still get the point. What does the sensor look like that is suppost to go in the cylinder head exactly?

Diesel911 · #11 03-27-2020, 11:40 AM

The Relay dose not have to actually be mad by Bosch. Relays and Temp Sensors are sold on ebay and Amazon. If you want the electrical connector they also have that.

The relays come in different amperages.

The little cube relays are also found on my 92 Chevy Astro Van were there is a row of 3 of them.

The pic of the relay is one I added to my Fan on my 86 Chevy Cavalier.

Hard to see but I did not use a connector (I have since bought some connectors) I used shrink wrap to insulate the female spade terminal s

Unfortunately when I did the job originally I had not insulated the connectors and the Relay bounced around and shorted and burned the fuse in and the Engine had no other fan then the Electric Fan.
That resulted in the engine overheating which split the plastic tank in the radiator and caused a head gasket leak.
A lot of expense and work because I did not do my job properly.

Mxfrank · #12 03-27-2020, 01:59 PM

Bosch stopped making relays fifteen years ago. They sold the business to Tyco. If you find a Bosch labeled relay today, it's very old NOS. However, the terminal identifiers on almost all relays today are DIN standard, so relays of any brand can easily interchange.

The relay you picture is weird, in that it has two 87 terminals. It's more usual to find either a single 87 contact or an 87 and 87a terminal. The latter is called a switchover relay: 87 is normally open, 87a is normally closed. When the relay is powered, that reverses.

Mxfrank · #13 03-28-2020, 08:24 AM

Again, the plug should be 22mmx1.5, which would fit the switch from a VW or Porsche:

https://www.pelicanparts.com/More_Info/823959481FINT.htm?pn=823-959-481-F-INT&bt=Y&fs=0&SVSVSI=2100

You need a 92C or higher switch, otherwise the fan will run all the time.

ASteele · #14 03-28-2020, 12:56 PM

ok thanks

ASteele · #15 03-28-2020, 01:03 PM

Quote:

Originally Posted by Mxfrank

Again, the plug should be 22mmx1.5, which would fit the switch from a VW or Porsche:

https://www.pelicanparts.com/More_Info/823959481FINT.htm?pn=823-959-481-F-INT&bt=Y&fs=0&SVSVSI=2100

You need a 92C or higher switch, otherwise the fan will run all the time.

So will this thermo-switch work? it says its specifically rated to 92C and once I install it i run two wires to the A/C Drier switch and wire it in parallel? But how do I wire it in parallel (Im a newbie when it comes to wiring lol)

https://www.*********.com/gbproducts/SC/118-08038902.html?utm_source=google&utm_medium=ff&utm_content=SC&utm_campaign=*********+Google+Base&utm_term=1983-1985+Porsche+944+Coolant+Fan+Temperature+Switch+Wahler+823+959+481+F+92+83-85+Porsche+Coolant+Fan+Temperature+Switch+1984&fp=pp&gbm=a&utm_source=google&utm_medium=ff&utm_campaign=*********+Google+Basecid=6774379819&aid=79287199093&keyword=297373227525%3A%3Apla-297373227525&kid=297373227525&gclid=Cj0KCQjw6_vzBRCIARIsAOs54z797csZNrZS_ozDf7ONO72ELnk4i8FzECdZN7Vc9OYbw_e4PhWDZlwaAnw_EALw_wcB