Recently bought a 86 firebird, been having fan issues. Changed out the relay, located right behind the right headlight, hoping that would be it. But I noticed that the wire coming from the coolant temperature sensor is broken off its harness. For the life of me I can't find the harness. Sensor is down between #6 and #8 plugs.

 

Trace the wires going to the relay, you might have to remove the sheathing.

 

Could it possibly be a ground wire? Needed to be ground to the body of the car?

 

Pretty sure this is the sensor that controls your temp gauge. (does on a 90) this is a one wire sensor. ground probably comes from the engine block. unfortunately, not at the car or could have a look and see where it runs. probably into a bunch of sheathing somewhere. maybe the area where it rests on the inside of the fender under the steering column.

 

Isnt 85 /86 the "weird years" where the single fan is controlled soley by the ecm or something?



My 87 was an apparently kinda rare single fan TPI was similar since the ecm controlled my single fan. Dual fans activated the second fan with the switch in the head though.....Mine had the fan switch and wire, but the wire literally went to a "dead end plug" that was sealed at the factory and not connected to anything since i didn;t have the dual fans.

 

If you have the fan switch between the #6 & #8 plugs, then there's nothing "weird" about anything. You have a fan switch. It works the relay. It requires a wire to do so. Same in your year as in any other year.

It is what it is.

The wire you're looking for will be dark green w/ white stripe. Probably would have come down over the valve cover out of the harness that goes up to the alternator but I'm not positive of that routing in TPI cars.

Alternatively, you could locate that wire at the relay, and trace it back toward the switch. You should eventually come to the place where some genius "improved" the car by HACKING on it.

Temp gauge sending unit (again, NOT a [mrspock] sen-sore [/mrspock]) is in the driver's side head, same hole in the casting; which puts it between the #1 & #3 spark plugs.

 

Yeah, what Sofa said. I was typing and about to post, when I saw that he did.

That's not a coolant temp sensor, nor is it for the temp gauge(sender for the gauge is between plugs 1 and 3). Between plugs 6 and 8 is the fan switch. It's mechanically controlled, and its single wire is a ground wire. It should be in a small loom of its own, coming out of a series of a couple of other small wire looms in that vicinity. If that wire is broken, then it might be tucked into one of those looms, or it might be hanging down in the vicinity of the starter, and it's probably very dirty.

 

Yep, got to thinking about what I said and was gonna follow up. was wondering if he had his cyl #'s off. nope, just me I guess. however, I thought my coolant sensor for everything else was mounted somewhere near the TPI throttle body, can't recall anything between 6 & 8, but, haven't been lurking around down there for quite a while.

 

Passenger btwn 6/8 is the secondary fan switch right above the knock sensor
Driver between 1/3 is for the gauge
TPI under the throttle body was for the ECM. that's the two wired weather plug one. I think tis next to the cold start injector for older models. I thin newer TPIS justt had a plug in place of the CSI

 

This is what im talking about

 

Definitely could be the knock sensor wire, which is blue in many cars. Definitely NOT the fan switch wire, unless you can trace it back and find it spliced to a dk grn/wht wire somewhere.

KS is on the pass side of the block, exactly halfway front to rear, between #4 & #6 cylinders, about an inch above the oil pan rail. Uses the same connector as the fan switch. Needless to say the 2 parts are not interchangeable: if the wire for the one is plugged into the other, it doesn't work.

The KS location was cleverly dreamed up in the early 50s, by engineers who had their eyes on the future development of EFI, but didn't want those bozos at Frod and Xler to figure out what they were up to. So they cleverly disguised it as a coolant drain hole for the 2½ decades before EFI was introduced. They even camouflaged it by adding a corresponding hole on the driver's side of the block, so people wouldn't think something weird was going on.

 

Interesting story from the 50's, Ah, the good ol days.. That is some forward thinking, waaaaay forward. Guess it must have taken an act of God to drill a hole in the block when the time was ready.....

 

The answer for a 1990 is both Temp and KS wires run down the main wire loom where the fuel injector wires feed and rests on top of the valve cover, and then more wires branch down the front of the engine block and then another smaller wire loom branch feeds those 2 items. It runs under the exhaust manifold along the block. Here are some photos, you can see the silver mechanics mirror pointing at the wire looms I'm referring to. had to break it out to find the wires. sorry, garage not lit the best for these photos.



The main wire loom carrying fuel injector wires and other wires - this is near the front of the valve cover.

The secondary branch running down front of engine block

Another angle of the secondary wire loom that runs down front of block

 

Well, I had a nice long post I lost lol

What induction you got? Im not sure if carb, tpi, or TBI? would be similar for that time... but mines a 87 TPI.

I'll try remember to get pics. My fan switch wire comes from the harness that goes along the frame rail that connects to the relay by the radiator. and was taped / loomed with the knock sensor wire from the factory . I'l ltry to get pics.

LB lookin clean / beautiful as always!

 

Ok got a new fan relay wired in. But still no fan. Next step I'll do is engine temperature sensor. This fan issue has me baffled. Someway somehow I will get it that fan running. I have went through every wire possible to make sure there wasn't any broke wires. So it continues until I get this fan running.

 

What process are you using to check operation? Temp getting over 220? Are you turning on the AC to see if that turns it on?

 

I'm guessing you got the single fan.

It would probably be computer controlled then.

 

The ac isn't hooked up, as of yet. Im going by the temp gauge in the dash. It has gotten so hot I can hear the coolant boiling in the over flow. I have noticed there is this plug with a single wire(in previous pic) this is between #6 and #8 plugs. Could it be a fan switch? We just changed the coolant temperature sensor. Haven't tried it yet since putting it in.

Sorry this is thenbest i can get.

 

That's very blurry... if its literally right next to the spark plugs that would be the fan switch.....the fan switch and the knock sensor use the same connectors... that looks like a replacement pigtail since the wire is white. What's it connected to?


What fuel delivery is it? TPI / Carb?

Single fan? Dual fan?

 

Single fan, fuel injection

that is the same wire

 

https://www.thirdgen.org/forums/cool...an-switch.html

ohm the blue wire to esc probably the same wire .

 

The engine is a 1986 305 TPI with a single fan? "Here's what happened..."

You're saying the single blue wire in your hand(in one picture) is the same single wire(that doesn't look blue) in the other picture, and it's coming from a pigtail that's connected in the cylinder head between plugs 6 and 8? And that wire is obviously not connected to the harness. To me, it looks like a replacement pigtail, not the original, so its wire color is probably not correct.

TPI Parts shows the 85-89 TPI knock sensor wire as white; my 87's is white, and yours should be too, if it's still original and in the proper location. And TPI Parts shows the 85-89 TPI fan switch wire as black; my 87's is black, so your original wire should be too, if it's still in the harness somewhere.

TPI Parts does show a blue-wired knock sensor pigtail but lists it for 90-92 TPI, 88-92 TBI and 4thgens; a green/white-wired fan switch pigtail for 88-92 TBI; and a light gray-wired fan switch pigtail for 90-92 TPI. But the connectors are all interchangeable, and electricity is colorblind, so any of them will work in either location. Your blue one might've been all that was available at the moment somebody needed to replace one of them.

It's possible that the pictures of the pigtails could simply be mixed up and not listed correctly at TPI Parts. But Angel is very meticulous, so I doubt he mislabeled the pigtails. And since my 87's wires match his listings, then I have to conclude that TPI Parts' listings are correct, which means your original fan switch wire should be black, too, and your original knock sensor wire white, as mine are. So your blue-wired pigtail is a replacement part, as I suspected. And at 36 years old, it's plausible that one or both have been replaced at some point. But if only one, then which one?

The knock sensor is located on that same side of the engine, but down in the block(not in the heads), above the starter. If it's plugged in, what color is the wire? If it's black(and original), then it's supposed to go to the fan switch. The white and black wires to each respective location should've been together in a small loom, after exiting a larger loom, near a junction of looms beneath the AIR 'box.' And they appear to be of similar length, which would make it easy for someone to have connected the black wire to the knock sensor by mistake. But if the knock sensor doesn't have a wire plugged into it, or it's a white wire, then you apparently still have a broken black wire to locate and possibly a white one too. But if the knock sensor wire is black, then unplug it and plug it into the fan switch, if it reaches, and try to activate the fan manually.

To activate the fan manually, get a random strip of similar wire and tap it into whichever wire you have running from the relay and plugged into the fan switch; black, if original. Turn the key to ON, but not the engine; ON, not ACC. Then ground the tapped wire to car's metal frame while the key is ON. IF the fan switch works, and IF the correct wires are connected together, and IF the relay works, then this WILL work. If it doesn't work, then you apparently still have a black wire to locate, or one of the other parts in the equation isn't working.

So keep searching for a broken black wire in a loom in that vicinity. And if/when you find it, then plug the first one back into the knock sensor, and connect your blue-wired pigtail to the newly-discovered broken black wire, connect the tap wire and ground it with the ignition ON to test the fan again. If you found the correct black wire, then the fan should work this time. Then clean-up the mess and move-on to the next project.

 

Thats just it, I have went through every loom possible...and no broken wire. There is a loom that is just in front of that blue wire area, with smaller looms going into the larger one. Today, I shall investigate that area for the fan switch.

 

Here you go. See that little triad of looms circled in the middle of my picture below? Now see the tiny black and white wires right in the center of that triad of looms? Those wires are coming out of the larger loom below them and going into the very small loom to the left. Those are the fan switch(black) and knock sensor(white) wires that you should be looking for, and that's where they would be if your wiring was still intact. The larger loom that the wires are coming out of contains the wiring that appears to be going forward to the fan electronics and rearward to the AC electronics, which would make sense. Those are the wires you should be searching for, and they've got to be in that vicinity somewhere. And when you eventually find them, it won't matter what color the wires are in the pigtails you have to connect to them; it's the pigtail that matters, and they both use the same pigtail. So if you use blue, or green, or whatever, it's no problem, but it will be on you to remember what's what lol.

 

thats what mine looked like! Mines an 87 TPI

but both my wires for the knock sensor and the fan switch were either black or dk brown not white.

 

Many (if not most) people dislike Wiring/ Electrical work/ repairs.
However, it can actually be quite fun!


Modifying Wiring (or making your own Harness), so that you can make Electrical Devises do what you want, when you want, how you want...
Is a ton of fun!

I like to add Relay Override Circuits to the Engine-Compartment Wiring/ Harness.
Here is the Connector for 1 of these Circuits below (on the Left, next to the Delphi ATC/ ATO Fuse Holder):



Just in case some of you are not familiar with the Delphi ATC/ ATO Fuse Holder; here it is below:



This Circuit connects to the Relay... lets use the Cooling Fan Relay as an example.
The 1st Wire of this Circuit connects to the Ground-Trigger of the Relay... with the Wire that goes to the Thermostatic Ground Switch.
The 2nd Wire of this Circuit connects to a direct Ground-Point.

Note: As well as using the Ground-Trigger; the Positive-Trigger can be used instead, depending on the Electrical Device that you are going to use.

Now when we want to use the Relay Override Circuit; just remove the Connector Cap and connect the RED Jumper-Connector (simply just a loop Jumper):



I like to install the Override Connector (with the Push-Pin attached to the Cover) to the Firewall, Relay Bracket, or Radiator-Support.




I provide the RED Jumper-Connector on a Key-Chain, labeled: "Cooling Fan 1".
I have different color Jumper-Connector Key-Chains for other Electric Devices, like a Fuel Pump (for Priming/ Flushing/ changing Fuels)...
Intercooler Electric Water Pump, or an Automatic Transmission Cooler Pump, Etc.

Now lets say you would like to run the Cooling Fan between Racing Rounds...
Turn the Ignition on (or don't if your Positive Trigger is always hot) and connect the RED Jumper-Connector.