This is somewhat of a long story, but I need some help. I have an '84 Z28. When I bought it, it had a 305 2bbl. I swapped it out for a 350 4bbl (edelbrock performer manifold and carbeurator). Shortly after this was done I moved and the car sat for 3 years. I finally got it back and started working on the engine. Whoever did the swap cut all the wires to the computer. Now it runs mechanically w/o computer. So I do not know what wires go where. To add to the problem, I swapped out my 85 MPH guage cluster for a 145 MPH cluster.

Ok, now that that is said; lets get to the problem. My temp guage was always topped out. I moved it with my finger and as soon as I turned the car on, it would top out again. I read that it was a negative short and fixed the wiring. I even swapped out the guage for another from a junk yard. Now the guage cycles when I turn on the car and falls to the bottom. After 20 mins or so, the car temp is still not reading 100 degrees. I live in Texas and it is 100 degrees here everyday, so I know that is wrong. So I changed out the temp sending sensor and installed a thermostat (whoever did the work on my car left it out completely). Still can't get the temp to register. What else could it be?

I just bought a new water pump in the hopes that it is not pushing enough water throught the system to get a reading. I am not a mechanic and am doing a lot of work myself. PLEASE HELP!!!

 

Does the gauge move when you ground the sender wire?

 

Many of the posts I have read say that there is one green wire. I have a black and yellow wire. How would I ground it?

BTW, I want to keep the origional guages. A lot of my greahead budies have suggested getting an aftermarket guage. I would like that to be a last resort.

 

The factory wire is green, it sounds like you've got the wrong wire.

 

The replacement wires for the sending unit are yellow and black.

 

To clarify, I have a female sending unit with 2 wires coming out of it. I just replaced what I saw was there already. That does not mean that this was the correct part and is most likely a change done during the engine swap. And due to the absolute hacking off of the wiring harness (it is truly that bad) I saw a yellow and black wire clipped off and it matched the colors on the new and old sending units. I figured that they were OEM colors.

 

The sending unit for the guage should have a single wire to it, and it is located in the driver side head between #1 and #3 spark plugs.

 

Remember, they cut almost every wire in the harness when doing the swap. Where would it come from in the harness? They cut most near the "trunk" (the tape wrapped part of the harness).

 

Yeah, sorry you have to deal with a hackjob. I looked at the wiring diag for your car:
http://www.austinthirdgen.org/index.php?pid=19

Dark green wire should be correct color. It's going to be small. It should come out of the main harness that runs over the back of the motor/bellhousing - the wire should originate from the main bulkhead connector (C100) on the driver side, should leave there in the main harness heading towards pass side over the bellhousing, but should exit right behind the driver head/valve cover, and should run up over the intake and down to the sender.

Don't know if that helps - 'should' isn't much help when there 'is not' anything left. But in that link, if you scroll down farther, there are pinout diags for the C100 connector as well - so you might be able to start there, and follow the wire to wherever it got hacked at, ground it with the key on and see if the guage moves any to make sure you got the right wire, and then extend it. You can ground it on almost anything metal that isn't painted or covered in oil, or you can clip an alligator clip from one end of a test wire to the copper of the wire and run it to the neg batt term.

 

It gets better, on that diagram I see the yellow and black wires for the coolant temp sensor unit. That is what I have been working off of.

 

That's for the ECM. They've probably cut the sender wire and left the sensor wire, not knowing the difference.

 

So the DRK GRN is the sender wire? Where does it attach to the engine?

 

To the coolant temperature sender between #1 and #3 cylinders.

 

OK I'll check it and mabye I can even find the wire?!?

 

Ok, I found a stud between the spark plugs for 1st and 3rd cylinder. It does not feel like it has a tab for the connection. BTW, I think I even found the wire. Could this be the sending unit?

 

Maybe. If there's any doubt, a new sender is cheap.

 

I am more concerned about the location of the stud. It is below the header and between the 1st two spark plugs on the drivers side. Is that it?

 

Should look like this:
http://shop.advanceautoparts.com/web...S_575658306___

 

Mine has a different look, somewhat like a spark plug end. Is the location right?

 

That sounds like a fan switch.

Do us a favor - look on the pass side head between #6 and #8 spark plugs and see what's there. Maybe the heads were switched when the motor was put together (which is no big deal, they are fully interchangeable, but puts the wrong sensors/senders on the wrong side).

 

is it in the head or the block?

 

in the head - pass side block there is one too, but it's the knock sensor - and it kinda look like a spark plug too (fan switch and knock sensor take same type of connector).

 

Ok, nothing on the passenger side. And the one on the drivers side looks exactly like the one in the auto zone pic, but with a different connector. The bolt it is attached to is the same size though. In think I will put one in and hook up that green wire I found just to see.

 

So the pass side head just has a plug in it I guess - because there has to be a hole in the head with something in it.

 

ok changed out the sensor and that fixed it, but now it tops out after I turn the car off. is that normal?