Me and my father have been rebuilding the LG4 in my '86 Firebird. We are finally putting evertyhing back together and are pretty much replacing every sensor and line, ect. we can. I want to run this engine through my 3 years of 60 mile a day commuting for college. We have the heads back on and what not, but there is a sensor in the passenger side head my father broke when he removed it. We can't find what sensor it is looking in our Chilton's Repair manual, and the parts house is clueless. I was wondering if anyone on here knew what sensor it was so we can replace it with the proper sensor to get this car running in tip top shape by the end of this or next week.

 

I could be a temp sensor, thats the only one I can think of right now that comes out of that area. can you post a pic of it?

 

If it is sitting just to the front of the starter, it will be the knock sensor.

 

In my 83 Z28, it was the fan switch that came out of the head, as I recall, it was between cylinders 6&8. The temp switch was on the driver's side between 1&3. The knock senser was on the block. Why don't you check the home page and see if they have any wiring diagrams you can pull up?

 

Right.... the one in the pass head is the fan switch.

The one in the block, right next to the end of the starter, is the knock sensor.

The one in the driver's side head is the sending unit for the temp gauge.

Wouldn't be the first time a parts house was clueless.... come here for the facts when you need them, I think we have most of the parts places beat.

 

I've been roaming these boards for a few months now. I've been finding out tons of information. Awsome job on here guys. And as for the parts house, I love the guys there, but they don't know much about the actual placement of parts, but they have a good idea on what is what, considering they were both mechanics. I thought it was the fan switch, but wanted to make sure. The knock sensor is in the block and the coolant sending sensor is in teh drivers side head, and has been replaced. We have replaced quite a bit on this car, and had the head professionally rebuilt. I'm hoping to get some more life out of this engine. I love this car to death, and have been taking good care of it. And I definately will be lurking/posting on here for opinions and information, as you guys have the best I've found. Thanks again.

 

two words, fan switch.

 

I defently hope so, off of the top of my head(I'm quite intoxicated at this point, thank you US governmant for making Molsen XXX legal in the us! Viva La Canada!) I can think of several things I was told by local auto parts store: "there is no such thing as a C-Clip", "Cold start injector?, You mean fuel injector", "They didn't have a carb version in 86, just tuned port, and MPFI.", I could go on but the extreme stupidity is hurting my brain. All I can say is Ahmen RB :hail:

 

I aslo thought it was the fan switch (broke mine while installing headers), but my fans still work fine. One mechanic told me it was the temp sensor for the ecm (said there were seperate sensors for the guage and the computer) that told the computer what temp the engine was running at, which is why my engine's running rich now (sensor istelling the computer the engine is cold, computer is increasing the fuel in the mixture). I wish I knoew for sure, I'm about to drive it to Florida and I need to narrow it down!

 

It's the fan switch.

In the later cars, the fan is controlled by the ECM (via its reading of coolant temp from the CTS) and that switch is just a "safety" sort of thing; or vice-versa depending on the parts choices. So you can unhook it and the fan will still work. However, in the earlier cars, specifically the carbed ones, the fan will NEVER work with it unplugged, except when the A/C is on.

That's how my 83 L69 is, for example.

 

If you have a TPI, there is a Coolant temperature sensor (CTS) mounted in the manifold just below the throttle body. There is a temp sensor mounted just above the #1 sparkplug that is for the temp gauge on the instrument panel. There is a heavy duty fan switch mounted between #6 & #8 spark plug on the passenger side. Just forward of the starter is the Knock sensor. You may have broken the knock sensor when you installed the headers

 

This sensor is actually in the passenger head... the knock sensor is intact. So, if this is a 'back up' sensor for the a/c fan, then theoretically I can leave it broken for a bit? I guess the car's running rich b/c of other reasons... I did yank all the smog stuff out.

 

OK, I have a question about the temp gauge sensor, I put new heads on mine and the whole for this has a "plug" in it with a square spot to insert something to take it out. Any Idea what size that could be and if not having it hooked up will cause any problems other than the guage in the car not working?

 

Is it an 'innie' or an 'outtie'?

Seriously.


If it is one in which the square head is sticking out, I'm not too sure what the name of the tool is. My father gave me one that goes on my ratchet. I do know it is a plumbing tool. You could probably take it out with an open end wrench as well. If it a recessed square shaped hole, a lot of head manufacturers have installed plug fittings that are removable with a ratchet and extension.

 

I thought of using a ratchet, but the "innie" is to small for a 3/8, and to big for 1/4

 

it should be a 5/16" square type pipe plug. I bought a special socket to remove mine, but the guys that were helping me had already rounded out the plug too much for it to work

 

Well, I just pressed my finger on it really hard to make an indention on it, then messured it. lol came out to 5/16" alright. I couldn't find any tools of that size, so while i was at Northern Tool, I looked through the Pin blocks and stuff and found one that was 5/16" so i stuck that in the hole and used vice grips on it.

 

I wish I'd have known the guys were trying to use a stud extractor on mine Square hole + round extractor = rounded plug
Now my fan switch is in the drivers head, and the sensor for the temp gauge is in the thermo housing.

 

Anything with a single electric fan relies on the switch in the pass. side head to turn on the fan at the appropriate temp. Dual fans the ECM controls the fans with the switch in the head as a "backup" in case the ECM doesn't do it's job.

On a single fan setup the switch is set to turn on the fan at about 220* (if it's a factory switch). If you turn on the A/C the fan will run constantly regardless of engine temp.

Hypertech and other aftermarket suppliers sell replacement fan switches with lower turn-on temps, if you don't want to wait until 220* for the fan to kick on.

 

More like 238 degrees F.

I got the part number from the switch in the HO 350 Camaro Conversion Kit and called around for a dealer that had one. It's listed as "95 degrees C". I'm also using a 180 degree thermostat. I like that combo much better than 238/195.

 

238* is only for the "safety" switch on a dual fan car. The ECM is programmed to kick on the fans at 228* so the 238* swtich is designed to kick them on if the engine overshoots this temp at which the ECM was supposed to turn them on.

Single fan cars the switch is a lower temp, around 220*. I have scanner-verified this with Diacom on my 92 RS Camaro with 305 TBI engine and single fan setup (all stock, everyting in good operating condition).

The gague on the dash may read higher (usually around 230-235*) but if you look at the actual temp provided by the ECM via the coolant temp sensor you'll see that it actually reads about 218* when the fan kicks on.

 

Well all things considered, 218º is still too high a temp. 170º is the preferred temp to run for most performance applications. I just wired mine up to come on when I turn on the ignition for now, until I either get an adjustable switch, or make a manual switch. So far it hasn't gotten over 160º (on the crappy gauge), even with the A/C on.

 

The guy who said something like it's not the first time a parts house has been clueless I have one comment. I work at Pep Boys and I find that statement absolutely NOT offensive at all. Most of the people working at these places are morons, I've been to Checker, Autozone, Strauss, and Pep Boys, along with numerous others, usually it's just some dumb kid working or some minimum wage loser. Anyway, just thought I'd get that off my chest. Oh, I don't work parts by the way, but I do yell at them a lot.

 

So you must be a cashier then. :P

 

Well, the good ol' '86 LG4 switch I had was 238 degrees F.

Who knows if that's what the factory actually installed, since I didn't get it until 13 years later.

 

Hey Dr. Dicknose, actually I work in service so yes I actually deal with vehicles everyday. Work on them, do minor diagnosis, whatever needs to be done. No I'm not a cashier that's a bitch job, something you probably have plenty experience doing.

 

Damn dude, don't get all pissy. notice the :P in my post, it was meant as joke.

 

My bad

 

yea w/e those things r comin out of the heads, i broke both of mine takin the heads off and puttin headers on, i just got 2 new ones but i have no clue which is which and which side they go on cause the boxes they came in dont tell u. so can u describe what each one looks like and which side it goes on? thx

 

the one on the drivers side should have the flat top, the passanger side one is just like a pin.

 

Go to napa for a replacement fan switch, i went to autozone (sold me a broken one then gave me guff about returning it) went to bond, didnt have one, went to napa had one for 9.83 and it works great

also if you broke the wire that connects to it (the plastic molding with the pin) I have no idea where else you can find one except for the yard, been wanting to get a new one for a while

good luck

if you already found one sorry for sounding like an idiot, didnt have time to read the whole thread =)

 

Check with Jet performance they make a fan switch that comes on earlier thereby keeping the car cooler. If you get too carried away with running cool the car may never come out of closed loop (depending on the year, whether or not you still have the computer etc, etc) Try this:
http://www.jetchip.com/

 

I just broke this sensor on my car (88 w/350 tpi engine). I broke it while taking out the stock passenger side header. So is this the fan switch or coolant temperature sensor? I attached two pictures to help show what it looks like. Does anyone know the part number? Thanks for any help!

 

Up on the cylinder head between #6 and #8, that's the fan switch.

 

Hi Damon, thanks for the response! Upon further inspection it was just a little bent and the wire still plugs into it and holds tight. However, is this the way the wire should look going over the switch? Looks like it's smashed.

Comparing my fan switch to the one on this website it looks like the black piece is missing on the top.
http://www.autozone.com/cooling-heat...?checkfit=true

It almost looks like I need the fan switch and the wiring that plugs into the fan switch as well. Can anyone post a picture or a link of what the wiring that plugs into it looks like?

 

Both the plastic surround on the switch contact itself and the plug that goes onto it are all smashed to hell. If it makes a good connection it'll still be functional, but if you want it pretty you're gonna have to replace the fan switch and get a new connector pigtail.

That switch connection is probably one of the top 3 electrical connections that regularly get smashed to smithereens on an old 3rd gen. Very common to find them in that sad condition, unfortunately.

 

Might not need to mess with cutting the wire or terminal. The plastic shell around most of the terminals in the car will come off and can be replaced without cutting off the terminal.

 

I wasn't even thinking about it when I was taking off the fan switch that all the coolant behind it would pour out. Lets just say I had a big mess

I manged to find these two parts at autozone. Looks like in order to change the busted wire I would have to cut off the old one and crimp the new one on.

Fan Switch
http://www.autozone.com/cooling-heat...?checkfit=true

Fan Motor Connector
http://www.autozone.com/electrical-a...2403_444142_0/


Still debating on if I want to change them out right now or just wait to see if the fan turns on after I get my headers installed. Same goes for my starter, that looked pretty rough but if it isn't broke then why fix it. Reading some of the other forums it looks like the fan switch controls the secondary fan and the ECM controls the primary.

 

Or not... See how the back half of the plastic terminal shell snaps together?



If you un-clip that part of the shell, the shell can be removed from the terminal. If it doesn't come right off, look closely there may be a locking tab that needs to be pushed with an awl, or thin wire like a straightened paper clip, then the shell will slide right off. This assuming of course that the physical metal terminal isn't damaged (they usually aren't).