It kicks on when I jumper the ALDL. Relay is good. Motor is good. New CTS and thermostat (t-stat was bad, but I knew that). It just gets up to temp, never kicks on, and just keeps getting hotter.

I have noticed the temp gauge seems a little jumpy too. It jumps back and forth a whole 20 degrees or so every once in awhile.

 

More info on the car would be great if you can provide it. Engine, make/model, options etc. Stuff that might be relevant to this anyway.

Run an IR temp gun on the thermostat housing and compare that reading to the reading on your gauge. Our gauges are notoriously off so it's possible yours isn't as hot as your gauge is reading.

Single or dual fan?


Does your fan(s) turn on with the AC engaged? They're supposed to.


If it's single, 90% sure even a 92 is controlled by a switch in the passenger side head, just forward of the dip stick but someone more familiar with it can chime in and that would be awesome.

If you have dual fans, the primary is run via the ECM and the secondary is run by a fan switch in the head (Same as a single fan set up is run on the older cars).

 

Sorry, been so long.

It's a 92 RS with a 3.1 V6. Single fan setup. Doesn't work with AC, but the AC doesn't work either, there is no belt on the pulley. No passenger head temperature switch on it. The CTS talks right to the ECM I believe, which activates the relay. It's ran very well until recently. I parked it because the fan wouldn't come on so it failed smog (overheating on the dyno).

After a year I just dug into it and it needed an ICM and a few hoses, a t-stat, some hood struts, a bunch of other misc. Poked around with my dvom, and did a CTS hoping it would fix it. I had power to it, the relay is good, the fan motor is good, thought it was pegged. But nope, still doesn't come on.

 

I do believe it's getting hot. It starts running pretty gutless and rough, and smells hot as hell.

 

Does the relay operate? (should be able to hear a click, might need for your assistant to jump the plug while you listen or even feel for it)

 

Bad ECU, been through this twice. If you hook it up to a scanner the temp will read, -32 degrees.

 

The system works, when he jumpers the aldl the fan comes on, bad ecu...

 

Another reason for a stand alone fan system....at least as a backup.

 

I second the bad ECU if all else runs well.

 

In the meantime I highly suggest wiring a bypass switch for manual control. That will keep the car driveable while you troubleshoot the problem.

 

You can just run a temporary ground to the fan relay, will activate every time the car is on, no need for a switch. Fine in the summer, really delays getting heat in the winter.

-Jim

 

Daaaamnnn... Don't say ECU. Tonight or tomorrow I'm checking the wiring harness in the loom that goes to the CTS. If it checks out... Guess I'm ordering an ECU

 

If you can hook it up to a scanner you will know for sure.

 

The scanner I have is OBD2 only, unfortunately

 

ECU's are easy to change. Used ones run about $70 on the classifieds here.

 

I see new ones on amazon and ebay for 100, going that route

 

So did you get a new ECU and did that solve the problem? I am having the same issue, fan won't come on at all. Runs cool on the freeway, once traffic hits, it goes up to 250+ until I get moving again it goes back to 220 or lower. 5.0 TPI auto 86 iroc single fan

 

For me the temp would get almost to redline before the fan would kick in then drop to 220 or a little below. I would first check that the fan motor is still working by grounding the fan relay to turn on the fan. I replaced it about 1.5 yrs ago with a used one I had. I believe you'll need to use a jumper wire and connect it to the green/white wire on the relay and a ground the other end of the jumper. If the fan kicks on then I would just let the car idle until it gets up to almost redline and see if it actually does kick on. If it doesn't you can always manually kick on the fan using your jumper wire to cool it down. Unfortunately the fan is completely controlled by the ECM in the 86. Here's a link to the wiring diagram for it http://www.austinthirdgen.org/?pid=19

 

In my setup 5.7L V8 beside the computer wire their is a backup coolant temp sensor on the passenger side that ground the Relay when it get to temp without the computer intervention check that this Sensor is not bad (If you setup Has it)

 

You have dual fans. On yours the comp controls one fan and the temp sensor controls the other. The 86 was an odd year and only had a single fan like the later RS's got and there is no temp switch. The ECM grounds the relay which turns on the fan.

 

Yes my 5.7L 89 GTA has dual Fan. but my 5.0L 85 has single fan and do have the fan switch in this case both the computer and or the switch grounds the relay.

 

This car has no switch only computer controlled.

 

Let me make sure I understand you... I have an'86 305 TPI. I can feel down there between 6&8 and feel what I believe is a switch. Feels like it has a strange connection at the tip, feels like the head of a nail. No wires going to it and I can't find any stray wires that might go to it.


You are saying on my '86 the ECM controls the fan which is controlled by the sensor in the intake and that I do not have to hook up that switch?


Thanks!

 

According to the wiring diagram and my experience that's what I'm saying. The full wiring diagram can be found here:
http://austinthirdgen.org/mkportal/m...ine_wiring.gif


What you may be feeling is a sending unit a PO added for a gauge or temp switch or something. I don't really remember what's between cyl 6 & 8 and I don't own the car anymore to go look.

 

Well, I replaced the fan relay and that seemed to fix my problem. Fan kicks on at about 230-235. It did get up to 250 at one point and then the fan kicked on, after that it never went higher than 235-240, in the drive thru on the way home it stuck around 220-230 sitting idling waiting int he drive through. I visually checked, and the fan was running. $15 at pepboys.

Pic of the part number on the box and the old relay.

 

Nice! That was an easy and a fairly cheap fix

 

haha hopefully one of many cheap fixes, but I have all these ideas bouncing around in my head, that equals one badass IROC, and maxed out credit cards to go with that badass IROC lol