PyRo9862

I turn the AC on and the fan turns on, so I know the fan itself and the relays are good correct?
What its been doing is about 80% of the time the fan won't turn on when it should and my car overheats. The other 20% it just works fine. I ground the wire for the fan controll switch and get nothing. I'm guessing this means its in the wireing, what should I look at? I hate dealing with wireing
Thanks.

Yes I tried it with the ignition on and with the car running incase you think i'm stupid .

305sbc

iTrader: (3)

what do you drive? year? induction?

You may need a new coolant temp sensor.

In many cars the ECM triggers the fan relay based on what it sees from the CTS.

PyRo9862

1991 Camaro, 305tbi.
Thanks.

breathment

so when the A\C is on, there is a 100% sucess rate with both fans coming on, and when the a\c is not on, and the temp rises there is only a 20% sucess rate? just making sure i am getting the facts straight

PyRo9862

Yes AC is 100%, its actually gotten worse, maybie a 5% chance of it comming on with the temp. Its a 91 RS, so only 1 electric fan.

PhilM

there is a seperate temp sensor for the fan, if I recall. the fan comes on automatically with the A/C. i ahd the same problem years ago, so i just wired the fan on a toggle switch...

HeavyBreathinRS

On my 90 RS w/305 TBI, the fan switch wire is dark green & white...probably yours is the same.
Are you certain you're grounding the terminal from the SWITCH (passenger side, between the last 2 plugs, just below the exhaust manifold) and NOT the temp sender switch?

Just a thought.

PyRo9862

Well I did it the ghetto way and spliced into the wires for the AC for a manual switch. The damn thing started working again right after I did that. Go figure.

The switch is right between the plugs, not below it? I think I had the wrong wire then. I had a blue wire on the passanger side just infront of and above the starter.

Zap Racing

Ground the green wire with a white tracer stripe from the fan relay that should be up close to the battery area. If you have 2 fans there should be 2 different relays. When ignition is on--fan should run. If you are sure that the correct wires are being grounded and it does not run, you either have a bad relay or fan motor. You can check to see if it the relay or fan by using test light or volt meter. Ground the correct wire--if fan does not run--check voltage at fan--if U have voltage, it is fan--if you do not, it is relay.

PS-- If the relay and the fan checks out, probably the coolant temp switch in the block.

TheGreatJ

The coolant temp sensor is directly between plugs 7 and 8. The sensor at the bottom of the block right above the oilpan is the knock sensor.

Tom91Bird

iTrader: (5)

Might wanna read that over again. We don't wanna start confusing anyone now. To be between plugs 7 and 8, the sensor would have to be behind the flywheel/flexplate since 7 and 8 are on opposite banks. And also, don't confuse the coolant temp sensor with the fan switch cause they're two different animals. The coolant temp sensor is in the front of the intake manifold and the fan switch is in the passenger side head in between cylinder 6 and 8

Tom

PyRo9862

Yeah I probably got them confused. When I get around to putting in the swaybars sitting in my basement ill find it and replace it, or atleast check it.

PyRo9862

Alright, its been a while, but i'm brining this back to life. I ghetto rigged a switch using the AC wires, and have been using that just to make it drivable for a while now. Its starting to get annoying, so tonight I changed what should have been the fan temp sensor or whatever its called. Right between the two plug wires on the passanger side. It didn't fix anything. So, anyone have any ideas?
Is that for sure the temp sensor for the fan?
There is bigger sensor below it, what does that do?
What does the one next to the thermostat do?
Could those be affecting it?

PyRo9862

This is the sensor I replaced, I broke the top of it off removing it, it had a flat top. This had a black wire going to it.
The sensor below it is a similar style with a green or blue (cannot remember) wire going to it, and its bigger.

And thats my camaro seat computer chair

CaptPicardsZ28

The picture you show looks like the knock sensor. On my 85 Z28 its near the starter.

White91GTA

Actually, the knock sensor is about twice the diameter of the cooling fan switch, and it is way shorter.

LAFireboyd

iTrader: (3)

Just to help clarify all the info you've gotten, the pic you showed is what you pulled from between plugs 6 and 8, right? That's the fan switch.

The larger sensor below it(near the starter) is the knock sensor.

The sensor by the theromstat that you asked about is the coolant temperature sensor.

There's also an AC pressure switch. It turns your fan on when you turn on the AC, which is apparently working correctly. Its location is hard to describe, but it's enroute to the AC system.

The wire that you ghetto rigged, was that the wire that goes to the fan switch(shown above)? And what wire or connector did you splice it into? Just curious... I'm getting an idea, lol.

PyRo9862

Thanks, I think since this post ive learned most of what there is to know about all these damn cooling sensors.
As for as ghetto rigging a wire what do you mean? My fan switch? It goes splices into the wires the AC uses to turn the fan on and crosses them when you hit the switch.

I guess the best way to do it would have been grounding the fan switch wire, but at the time I rigged this I was a little confused and thought the knock sensor was the coolent temp sensor, so when grounding that the fan didn't turn on, so I assumed a connection was broken or somthing and since I needed the car right away and didn't have more time to find out what was wrong I rigged that.

I think there is still somthing wrong, the new fan switch prevents overheating but still lets it get pretty hot. Ill probably go with a cooler thermostat and a fan switch that kicks in at a lower temp.

LAFireboyd

iTrader: (3)

Nope, nothing's wrong. The temp needed for that switch to kick on the secondary fan is like 240+ degrees. So it's gotta get real hot before that comes on, which is why it rarely comes on by itself. A different thermostat won't change that, but a different switch should.

Too bad you got tired of manually turning it on. That's what I was thinking of doing to mine. Since I've removed my AC, I'd like to use that fan when I want or need it, without having to change the switch itself.

PyRo9862

Well the switch is still there, and I still use it most of the time. Just not when I leave my car running to warm up it doesn't overheat if I forget about it. Or if i'm lazy and don't notice the gauge getting up there atleast it won't overheat.
And I only have one fan.

LAFireboyd

iTrader: (3)

I missed that "one fan" post earlier. But did you solve your problem?

The fan switch isn't computer controlled, it's temperature sensitive(stock, around 240 degrees). It's merely a fail-safe in case the coolant temp sensor fails, which is probably what's happened. The coolant temp sensor and the computer together are supposed to control your fan's regular operation, not the fan switch.

But as for a manual switch, yeah, I can see myself forgetting to turn off my second fan. The next thing will be overheating from no fans because the relay's burned-out, lol!

PyRo9862

The single can is controlled by the computer? Thats a new one. Wouldn't it throw a code if that sesor wasn't working though?

LAFireboyd

iTrader: (3)

You're the one with the single fan, so you should know, and you do. Sorry about that. That was a guess on my part that it would be set-up similar to my dual fans. But you're right, it's not computer-controlled. Too bad, though, because that would make for a nice safe set-up.