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  #1  
Old 06-15-2008, 06:18 PM
winmutt's Avatar
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Water temp wiring debacle.

Since the engine swap I am unable to locate the plug for the water temp gauge. On the old engine there were two sensors one on top of tstat housing and one on the drivers side of the tstat housing. On the new engine it appears there is only one. Also there is a sensor in the engine block.Which one of these is the proper water temp sensor and where does it plugin?
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  #2  
Old 06-15-2008, 07:22 PM
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AFAIK, the coolant temp gauge in the instrument cluster works off of a sensor in the block, about middle-ish, on the side where the IP lives. The sensors in the thermostat housing are for things like the electric fan, cold-engine lockout for the ACC, perhaps something to do with EGR/ARV.

Jeremy
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  #3  
Old 06-15-2008, 08:49 PM
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Quote:
Originally Posted by winmutt View Post
On the old engine there were two sensors one on top of tstat housing and one on the drivers side of the tstat housing. On the new engine it appears there is only one.
Is is possible (reference your particular situation) to exchange the thermostat housings?
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  #4  
Old 06-16-2008, 01:12 AM
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I assume the old engine is the '85. What year is the new engine?

If it is indeed the old one was an '85, I recall there are two sensors on the block one between #1 and #2 glow plugs and the 2nd located between the #2 and #3 glow plugs. The first one is for the EGR computer and the second one is for the temperature gauge. But you are saying there are two on the Thermostat housing? I know that one on the housing is a temperature switch.

The new engine depends on what year it is. If pre '84, again I recall there is only the temp switch on the thermostat housing and the temperature sensor for the temp gauge located between the #2 and #3 glow plugs. The temp gauge wiring is intertwined with the glow plug wiring.
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  #5  
Old 06-16-2008, 10:21 AM
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Thats what I was looking for. Ah temp switch on the tstat housing is for the aux fan? You are correct the 85 had two on the block. I'll see what I can track down. I cant find this wire in the FSM diagrams, anyone have a url w/schematic for this section? Or atleast the color coding? This is a ground type sensor like the others right?
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  #6  
Old 06-16-2008, 11:04 AM
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Quote:
Originally Posted by winmutt View Post
Thats what I was looking for. Ah temp switch on the tstat housing is for the aux fan?
No. The electric (as opposed to vacuum) switch on the thermostat housing is for the cabin blower fan. The switch prevents the fan from operating in the heater mode when the engine is cold. If you can do without that feature, you can simply connect the wire to ground.

Last edited by tangofox007; 06-16-2008 at 01:36 PM.
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  #7  
Old 06-16-2008, 12:31 PM
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ORLY? Thats odd, every 123 I have owned the cabin fan would come on regardless of temp. Oh ah. Is defrost the exception? Perhaps this would explain why I have to start out in defrost. Is this switch open or closed by default?
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  #8  
Old 06-16-2008, 12:38 PM
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It depends on the temperature. Open when cold, closed when warm.
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  #9  
Old 06-16-2008, 12:51 PM
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Whats the switchover temp? 32?
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1991 300D Nearly Perfect
1994 E320 Cabriolet
1995 E320 Touring
2001 Eurovan FOR SALE
1985 300D car, sold and missed.
OBK #42
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  #10  
Old 06-16-2008, 12:56 PM
ForcedInduction
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Cut in 91.4*f
Cut out 68*f
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Water temp wiring debacle.-picture-1.jpg   Water temp wiring debacle.-picture-2.jpg  
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  #11  
Old 06-17-2008, 05:26 PM
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Well its kind of fixed. Because the 85 has 2 sensors, there was a 4 prong (only 2 used) plug with the GP wiring harness. On the new engine it is only 1 sensor and different shape plug. I swapped out plug types and to the best of my knowledge have it wired correctly. However the gauge only reads to the first line and I know its hotter than that. Anyone have any suggestions? How can I check the circuit?
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1987 300D Sturmmachine
1991 300D Nearly Perfect
1994 E320 Cabriolet
1995 E320 Touring
2001 Eurovan FOR SALE
1985 300D car, sold and missed.
OBK #42

Last edited by winmutt; 06-17-2008 at 05:33 PM.
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  #12  
Old 06-18-2008, 04:40 PM
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No suggestions? Maybe dirty plug prongs?
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1987 300D Sturmmachine
1991 300D Nearly Perfect
1994 E320 Cabriolet
1995 E320 Touring
2001 Eurovan FOR SALE
1985 300D car, sold and missed.
OBK #42
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  #13  
Old 06-19-2008, 02:51 PM
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85 300D 4spd+tow+h4
 
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Anyone? Its summer and I would really like to know how hot my system is running.
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1987 300D Sturmmachine
1991 300D Nearly Perfect
1994 E320 Cabriolet
1995 E320 Touring
2001 Eurovan FOR SALE
1985 300D car, sold and missed.
OBK #42
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  #14  
Old 06-19-2008, 03:21 PM
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You're going to have to post some pictures. I am confused as to the difference in plugs shape.

The coolant temp sender has one plug.



And is the same as with all turbo years.

Unless you are talking about the other end? Did you swap out the ends or swap out the whole GP loom.
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  #15  
Old 06-19-2008, 03:30 PM
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Quote:
Originally Posted by DeliveryValve View Post
You're going to have to post some pictures. I am confused as to the difference in plugs shape.

The coolant temp sender has one plug.



And is the same as with all turbo years.

Unless you are talking about the other end? Did you swap out the ends or swap out the whole GP loom.
Just the ends. On the pre 85 engine it has a 2 prong straight plug, the 85 has a 4prong like the headlights or many other plugs in the car. I took the 2 prong apart and stuck the prongs in the appropriate holes on the 85. The 85 has 2 senders mind you, three wires in the GP loom. The other eng is 1 sensor 2 wires.
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1991 300D Nearly Perfect
1994 E320 Cabriolet
1995 E320 Touring
2001 Eurovan FOR SALE
1985 300D car, sold and missed.
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