My car has a odd issue I cannot figure out. I think I might have a bad temp fan switch, but even if I do, I think theres still something else going on.

When driving on the highway, or in city the car will spike up to 220, sometimes higher if I let it. The only way to turn on the fan is to turn on the A/C. Then it drops down to 160-180 almost instantly. That seems unrealistic for it to drop so fast.

I have replaced the thermo with a 180, I had a garage do a flush on it, i replaced the temp sending unit for the gauges thinking it was reading wrong, and still nothing.

Sometimes even with the fan on it still climbs high before dropping like a rock.

Any ideas?

Also, What way is the fan supposed to turn on the camaro? Is it supposed to suck air in and blow through, or conventional pull air through, and blow on to motor?

I switched polarity on the fan to try that and it seemed to help, but only been 2 days. Need more time to tell.

Any suggestions would be helpful. Thanks!!!

 

the fan sucks air through the radiator and blows onto the engine.
as for the other stuff i dont know-pretty weird-which temp sensor did you replace? theirs 3 of them and i cant tell you off hand which ones do what but one is on the passenger head the other is on the driver side head and then one is on the intake manifold. 2 are for the ecu and one is the guage
but it also seams like an electrical problem-im not good with electronics so i keep it simple-if something electrical is happening and it doesnt make sense, i check all the grounds then all the fuses then i usually call a friend. believe it or not but the grounds usually end up being the problem when it comes to "wierd things happening"
just some thoughts

 

It's actually not to crazy for the temp to drop that fast when the fan comes on. when I first got my 84 the fan was rigged into a toggle switch and ran hot when the fan wasn't on. I would always forget to turn the fan on and the car would get to around 220 or a little higher. I'd flip the switch and she'd rocket back down to 180.

 

Yeah, the fan wires are both black... one with a white strip and another with a red stripe. You would think they match up... Someone had them butt connected already, so I switched wires so they didnt match for the heck of it... Doest seem to make a huge difference.

I think tommorow I am going to swaop out the temp sensors and see how that works.

I leave my A/C on all the time (doesnt work, but turns the fan on) and it seems to run 180 all the time. Every once in awhile though even with the fan on it sneaks up to 220, but it always comes back down.

If anyone else has expiriences, or seen this before, let me know... I will post my findings if I get any also.

Thanks all!

 

Ok... so I decided to pull the "Coolant Temperature Sending Unit" as the haynes manual called it from the front of the drivers side cylinder head.

What exactly does this do?

I am replacing everything one at a time until my fan comes on when its supposed to, and I want to make sure what this exactly does.

http://www.yearone.com/serverfiles/p...=G14AQ169&trk=

Thanks

 

The sending unit in the driver side head operates the gauge, nothing more.

 

that is correct, the sensor in the side of the driver head is what works the gauge, but nothing else. i had some problems with my gauge a while back and it was due to a connection problem and the fact that the wire for that sensor was laying against my header

 

my car is doing the same thing so if you find out what the problem was please tell me. its kind of annoying to flip on the ac.

 

Need more info re: one or two fan set-up. For the single
fan set-up, the temp sending unit is in the block, by the
starter, and the knock sensor. It is a simple, temp activated
switch, closing (to ground) at its designated temp.
For dual fan set-ups, one is controlled by the ECM, the
other is controlled by a pressure switch in the AC coolant
line (also closing to ground). I don't think the single fan
control combines the AC or temp sensor to control the
fan, and I don't have any maintenance manual handy to
confirm this.

All of the switched ground lines, close a high current
relay to power the fans. Fan motors degrade, rather
than stop altogether, and then they draw excessive
current, which burns up the relay solenoid(s).

I just posted a more detailed explanation in this
section on diagnosing the problem. Hope it helps.

PS. If anyone need more info, I have a factory service
manual with detailed wiring diagraims, so PM me.

 

Thanks guys... I appreciate everyone's posts above...this really helps out a lot. It also explains after everything I replaced yesterday, the problem still occurs.

So the temp control switch for the fans in near the starter in the block? If thats the case, I wonder if I have a new problem. I have a 99' Chevy truck 350 bottom end, and everything is from the 305 LO3 TBI. So this might explain why my fan isn't kicking on, because the wiring harness is probably different for that if its even in the same place?

Also, what is the temp sensor that is in the intake manifold right up front? I thought that controlled the gauges?

Anyone have thoughts on either of these?

Oh, and to answer from above, I have a single fan setup.

 

No, the fitting in the block near the starter is the knock sensor. The switch for the second fan would be in the passenger side head. The temperature sensor in the front of the manifold is for the ECM.

 

Ok... so considering I only have a single fan, where would the temp sensor be to replace? (This is the one that activates the fan to turn on)...This is the only thing I havent replaced yet. It must be it... The relay is good, because to my knowledge the A/C shares the same relay, and that works when turned on. I know the water pump is good, cause I start it up cold with the cap off and I can see it is flowing very well.

I have a air dam under the car, and the radiator doesnt have any major visual signs of being old or bad. I just replaced the thermostat with a 160*, new water neck, new temp sending unit, and new temp sensor for ECM. I also picked up a autometer water temp gauge i am going to hook up to see if the stock one is accurate. I saw somone else on here said theres was way off.

I realize none of these things would fix the issue, but its nice to know when I do get it fixed everything will be new and functional.

If anyone could point me to this last sensor, I would appreciate it. If its anywhere other than the block, I should be fine since my block isnt stock.

Thanks again all!

 

Consulting the service manual for my 90 Formula:
Vin E (305 TBI, single fan), the fan relay is ground
switched by either the AC dash control, or the
coolant fan switch, shown on the passenger side
in close proximity to the starter. It may be in
the cyl. head, as opposed to the block. The
knock sensor is definitely in the block, in the
same general vicinity. There are 2 other coolant
temp devices: coolant temp. sensor input to the
ECM located by the AC compressor (not a very
definitive drawing, probably in the manifold), and
a coolant temp. sender input to the inst. panel,
located by the alternator, likely in the cyl. head.

Hope this helps.

 

Thanks l_dis_travlr This helps a TON. I know where to look now for certain for the Temp Sensor.

The other 2 you mentioned. The one that reports to the ECM is in the Manifold, and the temp sending unit is in the cyl head between the first 2 spark plugs closest to the front of the motor on the Drivers side. I have already replaced both of those.

My only thing left is to find out for sure if its in the Head, or Block. If its in the head, I can fix it. If block, then I am not sure what I can do considering mine isn't stock, but I will let you know what I find out hopefully tomorrow when I can take a look.

Thanks again!!