Need some help guys. What is the Coolant Temperature Sender? Isn't it the sensor? Checkout the picture below.

 

Third gen's have several different "coolant sensors" depending on
engine vin, etc. There can be an instrument panel sensor, an
ECM input, and a fan relay driver.

If you have the entire manual that the page came out of, at the
end of that section there will be a detailed description of all the
components, and reference to a component location section in
the back. If not, post some more specific info about your car
and the problem to be solved.

But caveat emptor. The amount of expertise here on 3-g can
be exceeded only by the navel-gazing gas-bags.

 

My vin is F. I got the picture from or very own tech articles. Im trying to figure out if there is a bad wire or bad temperaature gage. Here is a link so that you can see what the temp gage is doing...... http://www.youtube.com/watch?v=kDfATT_qprU

 

Senders are for gauges, sensors are for the ECM.

 

The one for the gauge, which that diagram refers to, is the one in the driver side cylinder head. Make sure the wire for it isn't shorting out, if it shorts then the temp gauge goes to full hot like that.

As far as the fuel gauge, it could either be the gauge itself, or the sending unit in the tank. I would try replacing the gauge first, because it's a hell of a lot easier to replace than the sending unit.

 

Well since it goes all the way up like that, then I can say that there is nothing bolted into my cylinder head. That must explain why it jumps up like that. I got a temp Sensor that is bolted into the intake manifold, (picture), but I dont know if that has anything to do with the gauge because it's not really a sensor, it's actually a temperature switch.

 

Aperion is (as usual) correct.

Upon further digging in my service manual, the "sender",
for both VIN F (TPI) & VIN E (TBI) is located in the
driver side cyl head, front. Mine (TBI) looks like the item
you picture.

The "sensor" is what's located in the intake manifold.
For TBI, its a single slip on connector.
For TPI, the manual shows some kind of weather-pak
connector, similar to the picture item.

So I'm not sure what you actually have, but it seems like
you're missing one, &/or one is in the wrong place.

Hope that helps...

 

The one pictured is the coolant temp sensor, for the ECM, not the gauge. The gauge sender should be just above the #1 cylinder, in the driver side head. It has a single wire connector, with a dark green wire.

 

Now that you mention it, I remember unthreading what looked like a temp sensor but without the housing, it was just an empty case/bolt. There was never a plug nor could I fing a weather pack connector. Enough said, Im missing that connector. I have no idea where to look for that dark green wire. Any clues to where I should look guys? Currently, I have a aftermarket Temperature gauge utilizing the threaded hole just above #1 cylinder. Thanks guys.

 

Do you have AC compressor? My GREEN wire runs from the temp sender up to a 1/2in plastic wire wrapping, which also holds inside, the wires for my AC copressor! From there, the 1/2in plastic wrap lays on top of the valve cover and runs down toward the back of the engine.

 

Thankyou my friend. Tommorrow, while there's light, Im gonna open up those wire looms to see what I can find. One more thing, when Im able to locate the GREEN wire, what type of "sender should I buy?

 

Ok. I found this sender unit's so I guess it depends on me on which one I want to get. How does everyone else's look like as far as the connector. Is it a single wire or double wire? In the picture, which one is used for our 3rd Gens?

 

Thats why he's the moderator LOL!!

 

In pic #2, of the 4 senders, MINE is the LAST sender(#4)

NOTE:my car is 87 5.7 TPI......year and engine may matter!!!

 

HHMMMMM. Any 86 IROC's out there that can help me on this one?

 

Single wire..... HHHHMMMMMMM

 

Both, Ward's 88 GTA and my 87 GTA are a Single wire(dark Green). I would think that yours would be the same!

 

AFAIK they're all one wire.

 

They are all single wire - the sensor is a thermistor, meaning that it's resistance changes with temperature. The hotter the temperature, the lower the resistance. The reason it's a single wire, is because it is wired in series with the gauge ground wire. The positive wire to the gauge has 12V ignition switched. As temperature increases, the sender allows more current to ground to the engine block, moving the gauge needle up. It's also why shorting out the sender wire (no resistance) causes the gauge to peg on full hot. Pretty much all temperature gauges work this way, and have for at least the last 50 years.

The CTS, which is used by the ECM to measure temperature, is also a thermistor. However, it has 2 wires, which both go to the ECM. This is so that the ECM can directly measure the resistance across the wires, by sending 5 volts through one wire, and measuring the voltage that comes back. The higher the voltage, the higher the temp.

 

Gentlemen, thanks for the information. You guys have been a great big help. Agian, thanks.

 

Have you found the Wire yet? Did you hook it back up?......any Update???

 

my wire is green for the sender. I broke the connector, got to wire a new one in. western union tie solder and hearskrink, the wire i kinda burnt, so im going to solder a new wire in, and try to route it away from the manifold. maybe some heat reflecting looming

 

Im about to go to my dads house right now to change my OEM fuel injectors with a set of Bosch III 22 lbs injectors. So while Im doing that, Im going to look for the green wire. Ill post an update on what I find.

 

Ok guys. Yesterday i replaced my 19 lb OEM injectors with a set of 22 lb Bosch III fuel injectors. BIG DIFFERENCE. I can now chirp the tires while in motion in 1st gear ... Check out the OEM and the Bosch III below. Anyways, I found this wire cut and wrapped around the wiring for the AC harness. Now Im color blind and not to good with colors but is it dark green?

 

That's probably it.

 

Where is the coolant emp sensor located on a 305 (F) engine in a 1988 firebird trans am?

 

In the front of the intake just under the thermostat housing.

 

'86 iroc-z 305 tpi, and my temperature gauge is constantly set on maxed out and never moves, ever. I bought a coolant temperature sending unit with the weird blade type connector that i have seen in pictures on this forum. The only problem is when i look at my left cylinder head there is nothing but cramped spaces (its so much easier working on a pickup truck) anyway i think i have identified the coolant sensor and switch above the water pump, but cannot find the sending unit anywhere. has mine dissapeared, am i looking in the wrong place, am i cursed with a forever maxed out gauge? I would really appreciate some help.

 

Sending unit should be on driverside cylinderhead. The wire for the sending unit is in the wire loom for the AC harness. I think its solid green. There is a wiring diagram for our 86 in the homepage "tech section." Look under electrical.

 

Ya driver side head. . I broke the connector and havnt soldered a new one in. I gotta rebuild it all anyways

 

you wont see it looking from above unless you put a mirror under the exhaust manifold with flash light, u'll have better luck finding it from under the car looking up in between spark plug 1 & 2.

my 86 iroc 5.0 tpi had the same problem, gauge was maxed out, would not move even with sender disconnected, i mapped out my sender and it was reading correctly, found no short in the signal curcuit(green wire), had b+ at pink wire, and had a good reference ground. got a used temp gauge from modern day muscle.slapped it in and worked out great.

 

im having the same problem, with temp gauge pegged. i also noticed that as soon as i pull my light switch to cut on gauge lights, my temp gauge pegs at the top. could not find wire shorted, and did install new temp sender. any help is welcomed. thanks

 

Your 85 IROC has a carb in it right? My best advice is to open up the wire loom tubing until you find out if the wire is shorting out somewhere. Its probably shorting with the head lamp wire. I could be wrong though.

 

no its tpi injected 305. but hey im thinking i will run my own wire from coolant sender and T off my oil pressure switch for power, but i dont know where to wire in new wire on ecm, do you have any ideas? which positions on ecm are wired for temp sender? can u help with that chevy86iroc-z. thanks

 

Yeah bro. Hold on. Let me look for something real quick.

 

Which model number is your ECM?

1985 pinouts (ecm #1226870)
1986-89 pinouts (ecm #1227165)
1990-92 speed density f-body (ecm#1227730)
1990-91 speed density (Corvette ecm #1227727)

THIS IS ALL WRONG BRO. DISREGARD THIS POST!!!!!!

 

Here is a picture of the 85 ECM. Im not sure if its just like yours but here it is...
Coolant temp signal C10 Yel 1.6(d) 1.6 (d)

AGIAN,,,
THIS IS ALL WRONG BRO. DISREGARD THIS POST!!!!!!

 

Okay bro. Here I go.
1. The COOLANT TEMP SENDER's Dark Green wire goes directly into the Instrument Cluster Panel. Its only use is to operate the temperature gauge.There is no wire that goes into the ECM.

2. Now the COOLANT TEMP SENSOR does go to the ECM. It tells the ECM when to turn on the cooling fans.

Sorry for the confusion. Hell I confused myself. I had to pull out the Haynes repair manual just to verify my own info.

 

okay, im a little confused also.... i ran a spare wire from my coolant temp sender directly to my ecm. and it made my temp gauge drop down like it was going to work, but when i turn my key to the closest position to start, it shot up. it did not shoot up when i turned on my lights or turned my key to the acces. (1st position). only when it cranked. so i read your post and i think that your saying if i run my spare wire from the sender straight to the instrument cluster, then it should operate as normal. when i turn my key to acc (1st position) but not start, my fan turns on like it's being told it's hot? what instrument cluster are you referring to, my dash gauges ? i have to think that my coolant sensor is working if it shuts on my fan, but my sender is faulted. any ideas chevy86iroc-z????? thanks

 

The instrument cluster is the gauages. You would have to find the drk green wire and splice into that.

 

The sender works by "seeing" resistance. If there is any resistance (usually in ohms) then you'll see the needle jump or move. When there is a voltage spike, the needle will jump or plunge. So thats why it moved. The you otta look for that dark green wire the should be in the wire loom of the AC compressor harness (if your ac is on the driverside). Put a multimeter on the wire and remove the gauge cluster. Now look for the Drak Green wire and insert one of the multimeters prongs into the connector that is associated with the dark green wire. Now put the multimeter in Ohm or resistance so that you can verify if there is resistance. If you get a reading, then the wire is good. Now get one end of the multimeters prong and ground it. if you get a reading, then this will tell you if you have a short in the temp senders wire lead.

 

hey, i finally fixed my temp gauge. i cut the dark green wire behind my instrument panel and ran a fresh wire straight from my coolant temp sender to the cut wire. works just like it did in 1985!!! thanks alot for all your knowledge. by pointing me to the instrument panel i was able to locate the wiring, when all this time i was thinking it wired to the ecm.thanks alot chevy86iroc-z!!!!

 

You got it! Hell yeah. Good job bud. Have fun with your 85 IROC bro.

 

Hi
I am trying to figure out why i am getting ses light on code 15 and came across this post so my be you can help me out.Before replacing cts i was getting code 15 and 42.After changing cts ony code 15.So i was reading this post and iam thinkin how to check if i may have any shortage in wiring from cts.I think I checked cts black wire with ground from battery and I got reading 14.35 V.I have to recheck it tommorrow.Anyway I need help with how to check if wires shortage or what else to look for.

 

Your code 42 is a bad connection with the EST wire. Or it can also be a bad ESC module. Either way, here is a shot of a book that I got. It'll help you troubleshoot the cause of the the error.

 

And TC 42

 

hey im not sure about codes and numbers. however i do know that my temp gauge was shorted out behind instrument cluster at the dark green wire that leads into module fitting on instrument panel. i would also get false reading on continuity checks, until i used the ground near my battery, thats when it read shorted to ground. at that point i wasted no time trying to trace wires i just cut the wire off my gauge cluster and ran a fresh wire from module fitting on cluster, thru firewall and out directly to coolant sender. car reads temp like new. by the way take one lead from your meter and put it on coolant sender wire(dark green)on the motor head . and take your other lead and touch it to same dark green wire behind dash gauges. if it reads 0.0000000 than your are good- no breaks. if it reads 1.0 its infinite means you have a break somewhere. at that point its very difficult to trace where the break is.

 

My 92 rs 305 TBI VIN # E has the single dark green wire the slide on female connector going to the sensor under the #1 cylinder.

 

Anyone with a part number for the above connector?

JamesC

 

I've looked but never found one. A female flag connector fits it ok, though.