I have a 1985 K5 Blazer, 305 V8. I am in the process fixing the heater. I flushed the Heater core and am now replacing the thermostat. I was going to replace the water outlet but there are two sensors on top I cannot figure out what they are. I am assuming one is a temperature sensor and one is possibly a temperature sensor switch from what i have seen researching on the internet. The problem is one side looks as though is was damaged and nothing was plugged in, the other side is a single stem plug which does not really match the parts I am finding for my engine and year. Also since i am on the topic what in the heck do they do?

I tried to search this topic so if has already been covered I appoligize.

 

Well I dont know what they look like but I can try and help you. One if probably the temp sensor like you said. It determines temperature of the coolant for your computer. The other single pronged sensor is most likely the temperature sending unit. This one is used for your dashboard temp gauge.

temp sensor -
Google Image Result for http://www.autopartswarehouse.com/images/apw_products/images/delphi/dets10075_updated.jpg?eqg61h7

temp sending unit -
Google Image Result for http://cdn2.iofferphoto.com/img/item/178/000/069/g_y03V.jpg

Is that what they look like?

 

ant 229,

The temp sending unit is it! that is the one pronge that was plugged in. The temp sensor, I really don't know. It looks like it is missing the top piece and is basically just a medal nub. It has not been plugged in since I got the Blazer. In my research the temp sensor you sent me keep coming up, so i will purchase it and see if it fits and try to find the loose conection.

Thanks for your help, that part name is huge!

 

If I were you I would try to find the connector that connects to it first. I wouldnt buy the sensor just to screw it in and not be able to connect it. It should look just like the top of the temperature sensor in that picture. Oval with 2 holes for the pins located on the temperature sensor Should look something like this:
GM 2 Wire Coolant Temperature Sensor Connector - The Repair Connector Store
And if you do find it, check and clean for corrosion. Only god knows how long that things been disconnected for.

 

I believe that is the connection and i do agree. I have been trying to replace/repair stuff like that a little along. It was a great find, it has 69,000 original miles which is good and bad, good low miles, bad low miles so alot of stuff has been neglected.

Thanks for the help if you don't have the exact part name sometimes it is very difficult to find, I spent an hour each at two different part stores and the internet trying to figure it out.

 

That was not it. One of the sensor ports is larger than the other! I beleive the smaller hole is the Temp Sensor that going to the temp gauge. It looks like it was modified to fit. The larger hole I don't have a clue since it appears to have been damged and was never plugged in to anything.