I've recently bought an '89 IROC 5.7 that someone had put a single fan in place of the dual setup. The provisions are there for the dual fan system, but only one connector is used. It's obvious that someone has done some wire hacking, since there is a thing guage red wire that someone has spliced into one of the fan relays that reaches around to a sensor (temp sensor?) on the d/s head. Why would someone do that? And why would they cut the orange wire for the fan relay at the positive battery terminal?

Tonight I upgraded my spark plug wires to Accel 8.8 mm wires. While around the plugs, I noticed what looked like a sensor that had broken and was just sitting there along the passenger side of the engine. It was between the two center cylinders, or thereabouts. What could it be?

Also, on the driver's side on what I think is one of the coolant temp sensors, has begun to fall apart. The plastic is all brittle and cracking. Is that what it is or should I be thinking something different?

Finally...lol... I was getting my a/c recharged today. When the a/c system was turned on, the single fan didn't turn on and caused the high side pressure to skyrocket. I'm guessing that the fan didn't come on because the relay power was cut at the positive terminal like I menioned before, although the fan does come on to cool the car. Could it be something else?

Maybe my best bet would be to just use the diagrams on this site to put the wiring back to stock. Is there a diagram that would show me sensor location? My new SPAL dual fans come tomorrow, so I would love to get this all sorted out by next week. Thanks for any help anyone can give.

 

Check out this link...

http://www.gmtips.com/3rd-degree/dox...des/sensor.htm

 

Cool link! Turns out I cracked off the top of my fan switch. That's what the broken part is. I already had a Jet replacement switch anyway so no big deal. I haven't run the car yet to check, but I pushed the spark plug wires on a little harder while I was under the car. One of them did push further back on the plug. Hopefully that was the problem.

The coolant temp sensor was destroyed. The previous owner just wrapped the green wire around the top! There is also that red wire that is spliced into the fan relay somehow. Tomorrow I'll see what that is all about.

The SPAL fans came today and they look great. I'll be paying a trip to the hardware store for mounting material. Then I guess it's wiring time.

 

Yay!

Sounds like you found the whole problem, as of wiring/ bad connection to a plug. Good luck and good job

 

One more SNAFU... I have a new coolant temp sensor for the one that seems broken, but there are TWO wires coming off of it. One is black and one is yellow. Isn't that the fookin switch for the water neck temp sensor going to the ECM? I needed the one for the drivers side of the block. Or, am I smoking crack and just supposed to ground the sensor to the frame and hook the green wire to the yellow? The instructions with the switch weren't very informative. Did the parts store screw me or what?

 

Yup, I got screwed by the parts store. Good job NAPA keep up the good work. I ended up fabbing a new clip for the guage coolant temp sensor.

Well, the fans won't turn on at all. I pulled off the cheap wire that was connected to the aforementioned sensor and clipped where it was spliced into one of the relay wires. Why would someone do that? I looked over the wiring and everything seems to be ok. From reading the posts here, it seems like the first thing that would go to **** is the relays. I'll replace them tomorrow if Autozone has them in stock. Should I get a fusible link also just in case? It was cut or pulled off the positive battery terminal when I got the car. I haven't checked what gets power and how much tonight cuz it's damn near midnight and it's dark. Tomorrow morning maybe I'll have a better idea of what's up.

 

When i replaced mine, i didn't see such a setup. Better take it back and rip them a new one. I got my relays at Autozone for $11 a pop... since Advance Auto Zone was out, they sell them for $9.99.


It sounds like when they had a single fan setup they tried to make sure ALL the hookups were in place for the ONE fan, which I don't understand. It's possible they tried to hook it up that way to make sure the fan comes on when the AC is turned on.

Primary fan = electronically controlled
Secondary - Temp controlled per manifold, or coolant temp forgot.

If you have maybe a bit over $100 bucks to spend, go back to a dual fan setup. The secondary fan is like a fail-safe to keeping the car cool..

 

I agree 110% with the dual fan setup! What happened is a previous owner had put in a single fan instead of a dual. I am trying to put in a pair of SPAL 11" fans and neither of them will turn on. But, I haven't begun to troubleshoot yet. Hopefully that will be the easy part.

I don't know what the expected result of running a wire from a relay harness to the coolant sensor for the guage would be.

 

Well, after i finish my shower and finish watching The Mummy REturns, I'll try to digup some pics on this board or on google of the wiring setup for the dual fans for you

Are you able to get pics of the setup the prev. owner has?

 

I've been following the diagrams posted here by mdformula, and also in my chilton's manual. I don't really want to go ripping through wire harnesses, but if I have to I have to. Thanx for your input so far rocs!

Nope, I don't have a digital camera. But EVERYTHING looked the same as a dual fan system except for that screwball red wire and one fan plug not being used. I'm gonna have to take a trip to get those relays today.

 

Well at least now I've got some sort of fan cooling going on! I believe I put the wiring back to stock routing. I bought the new relays after checking the old to see if I had power to them. I used a test light, and saw that each relay had power at the orange wire. I tried to jump both heavy guage wires to start the fan with the key on and then off. Neither worked. So, in went the new relays. Next I started the car, and turned on the A/C. No fan came on after leaving the A/C run for about 10 seconds. I shut off the A/C, and allowed the engine to heat up to about 220. BOTH fans now came on at approximately that temp. They stayed on until about 180* (new jet fan switch) at which point the secondary fan shut off. The primary fan ran for about 5 seconds more and it shut off as well. I remember reading that Danno said the computer will default if the secondary fan comes on before the primary and will cause both fans to run. I can't, however, find that thread to see how to fix it! Can anybody help me out here?

 

There is also a tan colored thin guage wire with a fusible link. It comes from the relay harness and goes into the firewall near the a/c evaporator. There is no power to it ever. Could this be the problem? Or, could the a/c switch itself be bad and not sending the proper information to the ECM?

Also, since someone did do some wire hacking is it possible that the ECU could have been damaged and that's the root of the problem? If I do need a new one it should be the 165 ECM correct?

 

I found a wire that had the outer housing worn away and allowing it to short out. Now the fans work like they're supposed to Thanks for all the help anyone gave!

 

I have an '89 IROC 5.7 also, and I replaced a sensor that sounds like yours - it's located between the last two cylinders just below the spark plugs on the passenger side of the block. It's called the fan temperature sensor and the fitting looks like the one on the knock sensor. Hope this helps if you haven't gotten an answer already.

89_IROC