coolant temp. sensor

[cochese]

hello,
i have a coolant temperature sensor (the one that's in the thermostat housing) that is not connected to anything.  it just has a    wire dangling off of it.  the ones that i have seen online seem to have two wires coming out of it.  mine seems to only have one wire.  the previous owner pigtailed a wire off of the main wire that comes out of the sensor - the pigtailed wire is the one that isn't connected to anything.  can anyone tell me what this wire is supposed to be connected to?  i can provide a picture if it would help.  thanks.

my truck is an 86 c-10
5.0 L 305

[VileZambonie]

please do post a pic. The coolant temp sender should be in the drivers side cylinder head for the gauge. Maybe he was trying to install some crappy aftermarket gauges or something.

[DnStClr]

That coolant temp wire coming from the driver's side head should be a green wire, and it goes directly to the instrument cluster elect. connector. Don't quote me on this, but I THINK the switch you're referring to at the thermostat is the thermal (or thermostatic) vacuum switch. Or at least it should be there. It's part of the emissions system and gets tied into the vac. going to the egr valve.
 Like Vilezamboni said- a previous owner might 've taken out the vacuum switch and installed an electrical switch to get a temp reading to an aftermarket gauge or something.   

[mikeith]

i have an odd question here as well (dont mean to be a threadjacker) but mine is makin my gauge read hotter than the truck is actually running and a mechanic said i just have the wrong sensor in? is he bs'n me or can it really be a wrong sensor

[VileZambonie]

They only offered a sending unit for the gauge or the switch for the idiot light so unless you have the switch... If you think it's the sending unit just replace it and see what happens.

[cochese]

alright, finally got a chance to take some pics of the sensor/sender that i was referring to.  it isn't the sender for the gauge, i've located that one (which doesn't work either).  i've labeled the pic for easy reference.  i'll refer to the letters in the picture:



A - this is the one i was asking about originally.  i thought it might be the coolant temp. sensor.  it does have two wires - one goes to D - what i think is the mixture control solenoid(?) on the carb.  the other one is capped off and not connected to anything C.



B - I included this to see if it might be the TVS for the EGR the DonStClr mentioned.  i included a bigger picture of this.  is there supposed to be a wire/connection attached to the back? 

i'm just trying to figure out what everything is so that i can check the routing of all the vac lines and make sure that all that emissions stuff is connected properly.  i feel that the truck is running rich, and wonder if it's because some of these emissions components are not doing what they're supposed to be doing.  as mentioned before, my truck has some rough idle issues and has a definite "flat spot" in acceleration between 25-30 mph.  i've also noticed that the EGR is sometimes functioning at idle, which i don't think it's supposed to do. 

i know my original question was about the sensor - A, and what it was supposed to be connected to, but if there is any info on the other items it might help me get an idea of how everything is supposed to be connected.  i hope it's not too confusing.  if it is, i can give additional info.  thanks for your time.

[VileZambonie]

LOL -Nice wire nuts! Did you buy the truck from an electrician? Your truck has a feedback carb so it should go to the ECM. If you really want to clean it up just ditch all that crap and put on a nonfeedback carb

[cochese]

it's funny you say that!  he is an electrician.  and that's just one example of his "handywork."
what else would i have to change if i went to a non-feedback carb?  would the ecm be looking for the carb, and would this mess anything up?  i would love to get rid of it all, but since texas now has emissions laws/checks, i'm afraid to change things up and not be able to pass the inspections.  what can i get rid of, and would a non-feedback quadrajet work, or do you mean replacing it with an after-market carb?  i'm planning on cleaning it up, but i just don't know what all i can get rid of.  i want to figure this out before i start pulling wires (and giant wire nuts .) 

[troop2]

The "B" in the picture is a TVS (thermo vacuum switch) and is made as pictured. The sender "A" in the thermostat housing is a temp sender to ground the solenoid on the carb. This solenoid Grey in color is an enrichment solenoid when the coolant temp is below ~70 degrees. Otherwise, the engine is hot and the solenoid is energized through the sending unit and leans the carb mixture for normal driving conditions. The carbs with a blue solenoid on the top and a white plug on the front drivers side is the computer controlled carb.

troop2

[cochese]

thanks, that helps.  so then the connection from temp sender "A" to the enrichment solenoid is correct? what is the other wire from the sender supposed to be connected to?  the ECM, as someone else said?  this is what i'm really trying to figure out.  it has never been connected to anything since i got the truck. 

so if this solenoid is not energizing, then the carb would be running rich all the time?