Hello

I'm writing about a 1990 Firebird 3.1 auto. The cooling fan will only come on when the car hits about 220 degrees even with the AC switched on. Isn't the fan supposed to come on as soon as you turn the AC on? That's what my '89 RS 305 would do...and pretty much every other car I've owned with an electric fan! The instructors in my friend's class (it's his car) insist there is no problem since the fan turns on at 220.

Is there a seperate switch or relay or something for the fan to turn on with the AC? Thanks

 

Yes there is, I am having the same problem and hopefully I will be able to tackle it tomorrow after work. A few months back my fan stopped coming on at 220 degrees so I always had to have the A/C on for the fan to be on. Now my fan stopped working all together. When I find the problem in my car I will let you know, most likely it will be the same thing.

 

Since your ac causes your engine to work a little harder your fan absolutely should come on as soon as you switch on the ac. i believe that there are two relays to run your fan one for the ac and one that comes on when the engine reaches temp. do you have single or dual fans? also have you checked the fuse? If the fuse is blown there must be a reason for it. It could also be the engine fan switch. Good luck!

 

Don't know much about the fan circuit on a v6 3rd,
but many electric fan cars also have a pressure switch
in the A/C system to turn on the fan when the A/C
high side pressure is up.

 

Thanks for your help guys! My friend just traded the car in yesterday and got a 2008 Grand Prix GXP! ha ha kind of a spur of the moment type of thing. He didn't like the V6 in Firebird and says he'll find a third gen Trans Am later.

So thanks again for your help. I'll definitely be back on this forum if I have trouble with my Camaro.

later

 

Hey AE Twitch
Thanks for your help...but my friend traded the car in yesterday on a Grand Prix GXP V8!! Really fast car!

I hope you figure out what's wrong with yours. Also I like the comment on your pic! It's totally true...a '95 v6 Camaro once beat me in my '89 RS 305 haha but everyone likes my car better!
Later

 

I guarantee you its the fan switch relay, mine went out to. but mine never gets to 220. Mine comes on at 190 and goes back running at 175-180 all the time.

 

It comes on at 190 degrees because thats when its suposed to i think. I know my 5.0 has a 190 degree thermostat so i guess that triggers the fan. however i believe that it should come on automaticly when the ac is turned on. It may be different with dual fan, i really dont know, my 87 has a single fan so thats what i base my observations on. good luck and let us know how the problem was resolved.

 

im having the same problem. itll turn on at 220 degrees but for me thats alittle to hot so i like turn on the ac(since my ac doesnt work) and let the fan stay on. but it seems no matter what position i put it on under a/c, the fan wont go on. by the way mine is an 86 iroc with single fan and tpi.

 

I dont know about the tpi but 220 sounds extremly hot to me, could be any number of things. Check the sticky on keeping you camaro cool. It has a very good procedure for replacing coolent componets with some really good photos on the process. the only thing i didn't see was replaciing the engine fan switch. on my car it is locatedon the passenger side of the engine under the exhast manifold between the #2 and #4 plugs.Good luck!!

 

I have the same problem, no fan at all. Does anyone know where the relay is located on a 91 RS?

 

Now that might be why my fan never shuts off.

 

220 isnt horribly hot, gm made these cars to run hot for fuel economy, if your cooling system is working proper(mine isnt) it should never get to 220, but if it does, its not really bad unless it goes over that, thats why the warning spot on the temp guage is around 260 or something(it looks like the redline mark on the tach) thats when you know your F*cked

my problem is the fan will not come on unless i turn the ac on, im hoping its just the temp sensor, my thermostat is newer but im gonna test that anyway as well

 

the only thing that controls the fan coming on is speed (over 40 turns it off i believe), ac being on (ac on == fan on) and the coolant temp sensor on the engine block (turns on at 220 or 230 i forget, turns off at 200 or 210).

If your fan works with the AC but wont turn on if the temp is getting over 230, then your temp switch is dead. Replacing it or rigging a manual switch to the relay is the best recourse.

Thermostat wise, you can tell if this is bad by running the fan and seeing how hot the car gets with the fan running. It should only get as hot (around 10 degrees over at most) of the thermostat's temp. Stock is 195, so if your car is >210 with the fan on, then you have a restriction or bad thermostat or poor coolant. This can only really be tested this way stationary if you have a manual fan switch.

If you are getting higher than thermostat temps (> 10 degrees over) while driving you have either an air dam problem, thermostat issue, restriction, or poor coolant or some other engine malfunction causing excess heat. At a speed over 40mph, you should be able to maintain roughly within 10 degrees of your thermostat temp. If you are overheating at cruise, first thing to check is the air dam, then lower rad hose collapse, then thermostat and so on.

220 is very normal though. The 195 stock thermostat will have you sitting around the 210 mark at best. You can use the 180 degree t-stat to sit closer to 200. Going lower is something only special builds need to worry about, as it wont help the vast majority of people, and will only lower engine efficiency. T-stat's start to open at their posted temps, they dont fully open for another 5-10 degrees. A partially open t-stat is just as bad as one that is partially closed, since your engine performs the best in a given heat range, and that range is in the 200-230 degree range, running lower does nothing but waste fuel, you wont make more power. If you could run the engine hotter it would be even better, that's why the newer high performance LS engines run hotter. It's all a matter of keeping your oil and components from breaking down under that heat.

 

safemode: let me run through exactly how my car acts maybe you could pm me if you know my answer right away.

car runs and drives fine, normal temp as long as im moving at a good rate of speed, but if i spend more than 10 mins in traffic my car gets way hot its up over 230, and the fan will not run unless i turn the ac on, after i turn it on the car drops back down to normal temp around 190-200(i think i have a 180 stat in it right now) and its fine,

i think its the temp sensor, i hope it is because i have 2 or 3 brand new ones in my parts bin

 

well, you have a temp sensor and a coolant temp switch. They're two different things. the switch is in the passenger side of the engine block (accessible from below in most cases). The switch is what is not functioning here. The sensor drives the gauge in the car, and that seems to be fine if it's reporting somewhat accurate readings. Pop in some of your other switches.

 

ah ha, see learn something new everyday, thanks for clearing that up, ill try it, it started pourin rainin so it aint gonna happen today

 

Check the relays by your headlights on the passenger side. What you can do is get a needle nose pliers or a paperclip and jump the connection, a set is for the AC (the AC uses 2 fans) and 1 fan for cooling, so only 1 fan should come on to cool your car down if you have dual fans. If you jump the connections with the pliers and your fans come on it's your relays, they are a cheap fix.... These cars do run super hot, my fans dont come on till about 230 degrees..... My fans also come on immediately after I turn on the AC ( to relieve the pressure in the condenser by cooling it)

 

ill check the relay 2 when its nice out again(ive got single fan setup)

 

i think i might have discovered something in my car, the relay i found on the pass side fender, has a wire running to the fan, when i unplug the connector there is a 20 amp fuse stuck in the connector, is that not a relay and its supose to have a fuse in it, or did the previous owner do a quick fix on it.

 

what i belive to be the relay everyone is talking about is at the front pass side near battery bolted to the fender

 

Some relays have been located there, and no there is not supposed to be a 20 amp fuse coming out of the sensor you are looking at. Also, and not to step on anyones toes, but there is no override for the fan turning off after 40 miles an hr.

Edit: OR that fuse controls everything your car needs to run. I wouldn't remove it.

 

 

yeah i dont think its right but im going to look at my wiring diagrams i have, ill take some pics tomorrow after work maybe it will help more

 

alright need more help here, like originally stated my fan would not turn on unless i turned on my AC, well yesterday i changed my switch on the pass side head, and took it for a spin, when i parked my car it was sitting at 220 but instantly shot up, i popped my hood and sure enough my fan still wasnt on, so i stood there scratching my head when all of a sudden my fan kicked on, i looked at my temp gauge and it was at 260(pegged to the top) would this tell me my temp sensor is bad or what

also it was a stock replacement switch, i was told i should have gotten one for a Grand nat or something because they turn on sooner, but idk


and here some pics to show you the relay im am talking about

here is the relay by the batt.


here is the 20 amp fuse inside that


and yes my car did turn off when i unplugged it while it was running, i know that was a stupid move but i wanted to find out, everything still works ok as far as i know

 

I have an 87 IROC with dual fans. Just noticed this morning when I started it up that the drivers side fan came on. The passenger side did not. I assume this is normal now from what I am reading? I actually thought a relay went bad. Will check the AC to see if it turns it on.

 

For dual fans, the primary fan is computer controlled. It won't turn on until some specific temp. (generally right around 220). The computer controls the fan by grounding its relay.

The secondary fan is controlled purely by to switches, one in the A/C compressor, that switches on when head pressure gets to a certain point, or, it can also be turned on by the temp switch in the passenger head. The computer pays attention to the secondary fan, and when it sees that it is on, it will also turn on the primary.

I haven't a clue about the single fan setup. I thought all cars that had A/C had dual fans? No huh?

 

And that is how TBI is. The only controller for the fan is the fan switch in the passenger side head. It's turn on temperature is 238°.
The A/C switch, unlike the v6 and TPI, directly grounds the relay, causing the fan to run regardless of the A/C system being charged or not.

That's all there is to the TBI fan system.

Want the fan to turn on sooner ? Tie in a switch for manual control or, change the switch out to an AC Delco D1855B (or equivalent) that has a 215° turn on temp. Just because the gauge is showing a certain temperature, that doesn't mean much. Accuracy was one thing not designed into a 3rdgen temp gauge.

The rest of this thread is full of mostly bad information and guesses on how the cooling system works. Search is your friend.

 

sorry for the super delayed response, but yes i got the understanding of the fan switch being the sole thing to turn on the fan for TBI, and i kind of figured that the Gauge isnt all too acurate but this happened all of a sudden it worked perfect telling me my cars fan turned on when it should before this, is there a sending unit for the temp gauge that could be giving me a 260 degree reading when it is really 238? or is the whole gauge just bad and i should get an aftermarket replacement that is more accurate

 

ok, let me reinstate my problem, lol

I am not the OP of this Tread i just didnt want to waste space on the board by posting a similar question...

that being said

I have changed my Fan Switch on the Pass head and the Fan still does not turn on when gauge reads 220-238 it turns on at 260(pegged to the top in the red)

my question, what controls what the gauge reads and is it a part i can change that may solve my Fan turning on at what the gauge says is 260

it doesnt bother me when a gauge is a little off, like everybody knows our tachs can be, but when its telling me my motor is about to boil over and die i freak a little even if i know its not

 

did a little investigating and found between 1 &3 on driver side should be what controls the gauge, could this be the reason my gauge is WAY off?

thanks

 

Yes, senders can become defective and cause the gage to indicate incorrectly.

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Happy Racing!

 

Ok... I'm not going to read through every post of this thread, I apologize is any of this is duplicate info...

That's not a relay. It's an inline fuse holder. Technically it's what the service manual describes as "inline fuse #3". It has nothing to do with your fan. In fact it supplies battery voltage to your fuel pump relay. That's why your car stopped running when you pulled the fuse.

Moving on... Many threads have been written about fan operation. Many diagrams have been posted too. There's no reason you shouldn't be able to do a search and study and learn exactly how the fan system works. With that knowledge, you should be able to determine what's going on and correct it.

The temp sender on the drivers side head drives the gauge. That's it. Whether you temp gauge shows nothing or it's pegged doesn't matter a bit to your fans. They're on completely different circuits. Unless your gauge is reading wrong I wouldn't worry about that sensor.

On your car three things control the coolant fan. The first is the HVAC controls. In norm/max A/C the coolant fan relay is grounded and the fan comes on. When the temp switch in the passengers head detects 238* or hotter, it grounds the coolant fan relay and the fan comes on. When the A/C system reaches 232psi, the coolant fan relay is grounded and the fan comes on.

Since your fan comes on with the HVAC set to A/C you know the relay, wiring, and fan motor is all good. So either your temp gauge is way off, or your fan switch in the passengers head is junk. Even the typical parts store replacement switch for the Grand National will turn on at a higher temp then it's supposed to. Pick up an aftermarket switch rated for a lower temp or buy the GN switch from GM.

 

thats the answer i was looking for thanks

ive figured my gauge is way off seeing as i changed the fan switch and the fan still did not turn on when the gauge was saying it was hot enough

that is good info on that fuse i thought was the relay everybody was talking about, the reason i thought it delt with the fan was because the wires to it run straight from the fan(or a group of wires that connect to the fan) so i thought it had to do with the fan, but thats good to know about the fuel pump

but i want to point out i did search this issue before posting, and i did not originate this thread i just jumped in to save space on TGO

 

If you're not sure if the engine is really making temp or your gauge is off, try a different means of measuring the engine temp.

 

a friend told me to get a laser thermometer to check, but is there any other way to acurately check the actual temp of the motor without buying a aftermarket gauge first

 

i will also take your advice and buy an aftermarket switch after i get my gauge reading near where it should be, since i know my switch is turning the fan on

do you or anybody on here recommend any aftermarket fan switch, i would prefer one that goes into the block like the stock one

ive seen the Radiator clip ones that people seem to like, but i would rather it be the stock location style Thanks