tj78_

yea, the other day (weeks ago) when we had that electrical problem across the north east.... i was on my way home and get stuck at a light, look down and what do you know? my temp is tacked!!!! i pull off to a gas station just in time to see steam comming from under the hood.... get out of the car and walk to the front to see the coolant flow on past the front tires......
luckily, NOTHING BROKE, the cap just blew and released the pressure..... so let it cool some, i filled it up again and figured if i can keep moving it will cool back down... nope, got stuck at the next light and had to pull off again.. so it got HOT, and i see no mixing of fluids so i think its ok/nothing warped... the first time after it totally cooled it was pretty hard to start, and then after that it started fine...

ANYWAY, so i talk to my gf's uncle, and he says, well try to turn on your a/c and see if it kicks in... and what do you know? it does, so its not the fan motor.... (wish i would ahve known that a/c kicks on the fan before... )

so its still broken, and i have been just leaving it on a/c (even though it doen't even blow cold, lol, doesnt really matter.....

so far i have changed the sensor on top of the manifold right next to the thermostat housing ( this is on a 305 TBI..
and that didn't work....

so i look in my book.. and see there is another sensor low on the side of the engine, but the way i understand it , that is for the guage only, so thats not the problem....( i don't think)

i just went back and got another sensor, but i can't find it in teh book to look up where it goes... but i figure, it has to be a sensor cause the a/c kicks it on, right? if it was the relay, then the a/c wouldn't kick it on still right?

whats going on here? what should i change????

thansk alot,
tj

Danno

TJ, what year, engine etc. It makes a big difference when trying to render advice.

tj78_

its a 90 305 TBI....

thanks in advance..
tj

305sbc

iTrader: (3)

It's not your sensor. It's actually overheating.
Have you checked to see if your pump is pumping coolant?
or for a collapsed hose?

tj78_

i didn't see a collapsed hose, and im pretty sure they are fairly new, i jsut repalced the radiator this spring.... well when i turn on the a/c so the fan is running, i have no problem it stays way down around 170 i think..... if i turn the a/c of, then the fan does not start if the temp gets over 230 or whatever it is... i wouldn't think its cause im not flowing coolant becuase if that was the case he fan wodl kick in at 230 but not cool the car well right???
how can i check to see if i am flowing coolant?

tj

even if im not flowing coolant the fan should still kick on right cause the sensor is reading at teh engine where the coolant is hot whether it is moving or not...? so if i wasn't getting any flow then, that woudl be another problem, and my fan woudl still ahve a separate problem...???

305sbc

iTrader: (3)

Yes you're right if it's just a problem with the fan (not) coming on when it gets hot then it could be a sensor or sensor wire problem.
I thought if a wire or sensor failed the system defaulted to fan-on but maybe not on your car.
I thought your fan was working correctly but I must have read your post wrong. Sorry.
I think the ECM uses the sensor on the intake manifold to control the fan.

305sbc

iTrader: (3)

Yes, ditto that.

tj78_

i already said above... its a 1990 camaro rs, 305 tbi

Thanks,
TJ

Danno

2 things control the cooling fan on the 90 TBI, A/C request and a cooling fan switch. The fan switch is located on the passenger side between cyls 6+8. It has a single wire, a brass body and black plastic around where the wire plugs in. Look to see if the wire came off. With the key on/engine off grounding that wire should run the fan. The turn on temp should be approx 234 degrees. If the fan runs when the wire is grounded, but overheats then suspect the fan switch. The switch runs the relay and fan so having the A/C on rules just about anything else out.

tj78_

thanks for hte help...
this is not the same as the guage sensor on the driver's side of the block with one wire comming out right? i thought that was the temp sender for the guage

is this the one?
http://www.partsamerica.com/SelectPa...20Fan%20Switch

what is the easiest way to get to it? behind the front tire? any tricks?

thanks,
tj

btw: i wonder why they put it there... you woul think they woudl put it near teh thermostat that the coolant flows through wouldn't you? i guess theoretically it should be nearly the same temp....

Danno

Guage sender is on the driver side between cyl 1&3, not the same one. From the bottom is the easiest. Drain some coolant first, otherwise you'll have it in you face if you have to pull the sensor. There will be 2 sensors there, one is the fan switch the other is the detonation or knock sensor. The fan switch is the smaller of the two as I recall. Actually being in the water jacket right near the cylinder is a very accurate place for it. While it's on a lift or jackstands with the key on engine off you can ground the wire on the fan sw and the fan should come on. If it does not then it's a wiring problem from there to the fan relay. If it runs, replace the switch. NAPA stockes them at $19, and they have 2 different temps if you want. They have the stock 234 and another at 215 I think, it's been a while. Make sure the coolant level is correct and you system is holding pressure. I just fixed a friends Taurus(yeah, I know) and his fan would not run. He had a crack in the rad and was losing pressure, not much coolant loss but the fan just would not run even though it was overheating. Keep all the practical things in mind when servicing a cooling issue. Probably a good time for a flush and a new stat and rad cap. LOL, keep us posted.

tj78_

great, that was perfect explination/..... so with the engine in the totally off position i just ground the wire to the frame adn see if it comes on... if it does come on then its the switch, if it does not, then its wiring...
thanks,
tj

meridius

The ignition switch has to be on while grounding that wire to see if the fan comes on.