Engine temp sending unit

[OUbesto]

Ok, please take a look at attached pic of my engine's temperature sending unit located near t-stat housing. By now you may have noticed there is no wire connected to it, right? So how is it that my dashboard gauge shows accurate temperature????? Is there possibly another sending unit somewhere else that is connected????? Or is it some new techie unit that works c10 via wifi

[BrianG]

Look in the driver side head between cyl one and three. That's where it should be.

[swamp rat]

^^ x2!

[OUbesto]

Thanks guys. Should both sending units be wired or just one of them ok?

[Mrturner1]

X's 3 lol mines the same way. Was in the manifold but that's just a plug now. New ones in the drivers side head, more accurate reading. Just one wired is fine

[OUbesto]

Thanks!

[Newguy71]

Mine is below the manifold? I honestly don't know what I'm talking about, new to cars in general. So in my terminology, my sending unit is located on the passenger side head... Even that may be wrong. Ha. But my question is where on top should it be? Driver front? Passenger rear? On another note, I grounded out the 12 volt peg of my temp gauge... Before I did this, I could ground the temp wire under the hood and get it to peg hot like it should. After shorting the gauge, no luck. How much damage did I do? Did I burn up the ceramic resistor? Fry the gauge altogether? I'm freaking out a little because it was an all original cluster.... ��

[GASoline71]

No idea about the gauge Newguy17...

Temp sending unit's don't belong in the intake manifold on these old engines. Put it in the drivers side head where GM intended it to be.

Gary

[dmjlambert]

Newguy71 I'm having trouble figuring out what you're trying to say about grounding out the temp gauge. Or shorting the gauge. I suppose it is possible you burned out part of the printed circuit of the instrument cluster. That should not be a huge deal, because the printed circuit can be replaced. Or you could have a burned out fuse. Check your fuses. 3 amp Cluster Feed fuse. One terminal on the gauge should have 12V on it. The other terminal is connected to ground through the sender, with variable amount of resistance depending on the temperature.

If you remove the instrument cluster you can examine it closely, and test the printed circuit, checking continuity of each trace with a multimeter. The repair or replace the printed circuit as needed.

If you have the instrument cluster with temp gauge, the sender for that on a 350 engine is on the drivers side of the engine between the front two spark plugs. It is OK if it is somewhere else, but I believe usually it is in that position. You didn't mention what truck you have or what engine. Pictures are good, let's see what you have.

[Boog]

Welcome newguy.
Also note there are different temp sending units. One is for trucks with a factory temp gauge and one is for trucks with a factory temp light. I was recently sold the wrong one for mine.

[Newguy71]

Thanks guys! Sorry, I have a 71 Sierra 2500 2wd fleetside? Not sure what the fleetside means. So I was trouble shooting my temp gauge. I could get it to peg hot when I grounded it so I replaced sending unit which I now think is definitely in the wrong spot. To further trouble shoot, I put a 300 ohm resistor in place of my sending unit. It stayed pegged cold. So then I thought maybe I don't have a solid ground. Hooked a jumper up from ground to the 12 v peg by mistake. Now it's not moving at all. I believe it came from the factory with a temp gauge. There's no dummy light. I saw a thread on here describing like a 15 step process of removing the instrument cluster. How difficult is it to remove the cluster? I'm afraid I'll take it apart to fix the temp and end up with no gauges.. to your comment about the 3 amp fuse, what else does that feed? Everything else seemed to work afterwards. All gauges, dash lights... Pictures will have to wait for daylight.

[dmjlambert]

The 3 amp fuse feeds the brake warning light and the fuel gauge. I'm thinking it is most likely the fuse is burned out. It was actually its job to burn out when you grounded the 12V side of the gauge. Good job! You can check fuses by turning the key to the on position, and clip the neg lead of a multimeter set on a DC volt range to ground, and touch the pos lead to each side of each fuse. If a fuse reads 12V on one side and 0V on the other side of the same fuse, that is the burned out fuse. You can use a lighted test probe in the same way. If it lights for one side of the fuse, it should light for the other side as well. The burned out fuse should be labeled Cluster Feed.

I took out my instrument cluster a couple of times, and I don't remember having a lot of difficulty with it. On my 1969 truck the speedometer cable unscrews, and the oil line unscrews, and I was very gentle with those. I think on some year models the speedometer cable may unfasten a different way, I'm not sure. The cable of wires has a couple of wings you press in to release it, if I remember correctly. After removing the screws that hold it to the dash the cluster had to be wiggled around and figure out the correct angle to pull it out. I had to remove mine because it had multiple problems and I just had to examine the circuit closely and make repairs. You are probably not at the point of needing to remove the cluster yet. Note that if you start the engine with the instrument cluster removed, oil will flow out of the oil pressure gauge line. I had to move my truck with the cluster removed, so I initially made a little mess, and then put an oil catch pan under the oil pressure gauge line for my brief engine run.

Fleetside means the outside of the pickup bed is smooth, and does not have the fenders sticking out from it like the stepsides have. It is the body styling. I have a fleetside also.

Feel free to start new threads with new questions that you may have. I am a newbie also, but learning something every day. I have learned a lot about the temperature senders, gauges and lights as I work through issues on my truck. There is also a search field at the top of the forum page where you can find threads that contain a lot of very good info from knowledgeable people around here. If you add a post to an old thread, the people who were originally on it may not be active in the forum any more, so in those cases it may be best to just start your own new thread. This thread is not extremely old, but getting there.

[Newguy71]

Thanks! I'm thinking my fuel gauge just went bad too so blown fuse seems likely. And thanks for the thread advice. I'm still getting the hang of how to search and stuff. When I originally started, I found 10 V instead of 12 on the temp gauge, that was with the key turned to aux. My fuel gauge seemed to be working until I filled up the first time. I put like 20 gallons in and the needle went past the full mark and is sitting at about 3 o'clock on the gauge. And it has not dropped since I've been driving it... I was told it has a dual tank but there's only one fuel neck which is located on the driver side cab. I have a fuel switch in the floor by the door which says left main right.... I don't understand that either. I'm kind of off topic here; my apologies.

[dmjlambert]

There are things to learn about these old trucks. There is a lingo associated with each part of the truck and it's hard to search until you figure out the lingo. It is necessary to figure out the differences between the way the truck was made and the way it is now, so you can figure out the parts to get and what parts match up with other parts. An example on my truck is although I have the original engine, it was rebuilt with new heads and the temperature sensor threaded hole is smaller in the new heads. There is no smaller sensor that will work with the stock temperature gauge. So, I need to deal with that. Adapt. There's lots of stuff to study. I have crawled around under the truck and looked and stared for hours, and came back to the computer and figure out how the stuff works. Same thing under the hood and inside the dash. Figuring out what all documentation is available and how to look it up, what sort of diagrams to download or order, is a job too. Just keeping bookmarks organized is another job. I'm bookmarking stuff like crazy related to other people's experiences and methods while I plan for stuff to do to my truck, and keeping track of what sites sell stuff I might need to order online. Yeah it is easy to drift off topic. I suppose we could have a thread about how to deal with the new old truck experience as a newbie. Welcome to the forum and congratulations on getting the new truck. I know everybody here would like to see a new thread from you about "Hey check out my new truck" with pictures.

[Newguy71]

Yea ill do that soon as I can. This morning I checked my 3a fuse and it was good but I had no voltage to it... So now I need to trace back and see where my voltage went. Every thing else on the fuse block seemed to have voltage, but I didn't check every thing. I have the wiring diagrams but there's like 4 flavors and the Verbage at the bottom didn't make sense to me. It says things like CA30 (03) and Ca-KA10-20 does that mean anything to anyone? I'm not sure which one is mine but they seem to all be relativity the same... Anyways, gotta do family stuff today. I'll start a new thread with all my questions and pics as soon as I get a chance.

[lugnuts09]

Hey guys I have a 69 c20 and I'm having a hard time finding a temperature gauge wire for it. It didn't have a wire when I purchased it. It has an actual temperature gauge not the light. Any help would be greatly appreciated.

[Boog]

The temp sending unit wire should be a dark green one from the bulkhead connector to the temp switch shown in front of the engine in this diagram.
In this color diagram that wire is shown as 20DG. It's the same for a temp light or temp gauge. It's the sending unit that is different.

[Newguy71]

Boog could you please share a link with that color scheme? I downloaded that picture but it's too blurry to be useful. I like it because it shows how the engine compartment ties in with instrument cluster. Thanks!

[Boog]

That thing is HUGE. It lost a lot of clarity in downsizing. Jimbosprint posted it in another thread. Lets see if this works.

http://67-72chevytrucks.com/vboard/s...49#post7809749

There should be a way to cut this diagram into 2 or 3 sections to print in order to maintain this quality view. However I do not know how.

[lugnuts09]

Thank you for the diagram. I'm having a hard time finding where to buy the wire. I've checked oreillys and lmc but could not find it.

[dmjlambert]

Originally Posted by Boog

There should be a way to cut this diagram into 2 or 3 sections to print in order to maintain this quality view. However I do not know how.

I cut it and did some minor editing to make the cut look clean, using my Mac. This looks great if you take it up to FedEx Office on a USB stick and have them print it on 11x17 sheets in laser color. It was inexpensive to get prints from them.

page1

page2

Thanks very much to jimbosprint. The cut version has lost just a little bit of resolution, I was not able to fix that.

[Boog]

I'm sure you will have to make your own wire or snag one from a salvage yard.

Good job there Lambert.

[dmjlambert]

Originally Posted by lugnuts09

Thank you for the diagram. I'm having a hard time finding where to buy the wire. I've checked oreillys and lmc but could not find it.

Forum member gmachinz apparently makes wire or relay kits as mentioned in this other thread, and he mentioned SXL or TXL wire being appropriate under the hood.
http://67-72chevytrucks.com/vboard/s...d.php?t=728103

[lugnuts09]

Thank you all for the help. I believe I might have found what's left of the wire in my engine bay lol. I will keep that guy in mind for buying a wire after I see kfmbfm mine is salvageable.

[lugnuts09]

Does anybody know what the fitting looks like that attaches to the this? It's the temperature sending unit.