OK guys...ANOTHER cooling fan problem for you. I've done all my reading of past posts and I'm still stumped. 1990 iroc, 305 tpi speed density....duel fans. OK.... primary fan will not kick in....secondary will with a/c on....so we know the switch in the pass. side head is good. CTS is new. primary fan will come on when the a/b terminals of the diagnostic port are jumped (like you were pulling the codes) so we know the fan itself works and the relay works.....checked fuse box...all ok down there ....any ideas why the ecm won't turn it on?

 

You do realize the ECM only turns the fan on after the block has melted, right?

Ok, just kidding, but the fan turn on point is obnoxiously high, up in the 230's. The only way to test it would be to falsify the signal to the engine's coolant temp sensor (to make the ECM think the block has melted and turn the fan on to solidify the new art form) or just plain let it idle until it really does get that hot. An ALDL scanner will let you know if the ECM is seeing the right engine temperature. If it is, then everything should be fine.

By the way, the sec. fan is kicked on automatically when AC is on, it has nothing to do with the fan switch in the side of the block. The fan switch will turn the sec. fan on, also just after the block melts, actually also in the 230's.

solutions
(1) DIY-PROM to turn the primary fan on at lower temp
(2) use a GN fan switch to control sec fan (see my sig)
(3) do nothing
(4) use a 180 stat, a DIY PROM, and the GN fan switch together

 

ok....so the sensor in the pass side head will control the primary fan as well??? I thought only the cts and ecm trigured the primary. Lord I hate the thought of trying to get back in there to change that sucker...I still have all my A I R and emsions stuff....there is just no room on the pass side....sigh... Thanks for the input.

 

there is at least two temperature sensors.

one, the computer reads, and uses it for fuel mix and for turning the primary fan on and off

the other is a switch to control the secondary fan. it's just an on/off switch. it's pretty easy to get to, if you do it from underneath. don't even bother with up top.

i guess my previous post wasn't so clear, i meant that the secondary fan coming on with the AC has nothing to do with the switch in the side of the block, although that switch will also turn the fan on at a preset temp, regardless of AC.

 

guess I'm off to replace the switch in the pass side head.....so I don't look like an idiot....what do I call this switch??

 

radiator fan switch

you can get the stock one (which comes on at like 235 degrees) or a GN one. If you get the GN one, it will come on, but never go off, with a 195 stat - you have to run a 180 stat to make the GN switch work.

I don't have the part number andy for the GN switch but you can search and find it on here, it's the switch for an 80's turbo regal/grand national.

 

I recently installed the GN switch and a 180* Stat in my 87 Camaro (383 non cc) and I like it much better. I also have a Toggle switch, which is something you're wife can forget.

Got mine from a local Auto Parts store:

CarQuest Brand
Fan Switch
1986 GN (No doubt the same as 1987)
P/N TS-136
About $30

Thier book said:
ON 220*
Off 204*

There are a number of solutions to this problem and perhaps even better ones, but so far I am much more comfortable.

 

so how do you wire the temp switch? i'm thinking you can just run a hot wire to one terminal on the switch and then a wire from the second terminal to a relay for the fan and when the switch closes, the fan kicks on. where's a good place to put the switch in?

 

huh?

you put the GN fan switch in place of the stock fan switch. it is a bolt in swap. you are just replacing the factory fan switch with another one that looks and connects the same, but turns on at a lower temp.

 

i don't have a switch, didn't come with my engine, so i want to put one in. i just have a coolant temp sensor.

 

Ukraine, I'm a little confused, but that doesn't take much sometimes.

On the assumption that you have an Electric Fan, that works, I will assume that you also have a 'Fan Relay' and a 'Fan Switch' someplace.

What do you see on the side of the passenger side Head, between #6 & #8 cylinders (not the block)? Typically this is the location of the 'Fan Switch' and the one that I am most familiar with.

I believe that this switch, on some applications, is mounted towards the front of the intake manifold, either on the Stat housing or the Manifold itself. I'm not to familiar with this applicaton though. What engine version are you running?

The switch has a 3/8 pipe thread (Brass) that screws into the Head. The outer end is Black plastic, something of a Mushroom shape with a small hole in it. This is where the electrical connector snaps on. Typically, this connector has a Green wire that feeds back to the 'Fan Relay' and provides a Ground to the Fan system, but only within a given tempeature range.

See if the above helps any and, if not, give us some more info on your engine and induction system. Are you running Single or Dual Fans??????LOL

 

on the pass. side is where i put my coolant temp sensor (bt/n 6 and 8) on account of a pipe plug being in the driver's side head where the temp sensor should go. there is no fan switch either because the previous owner of the engine pulled it or corvettes had them somewhere else. this a tpi engine but i'm using a carb on it for now.

the wiring in the car (which i got seperate from the engine) is really hacked, i haven't traced the fan wiring yet but i think it may go to a switch on the dash.

so, where can i put the fan switch and is how i previously described a correct way to wire it?

if you're still confused let me know.

 

Ukraine,

The Gizmo you refer to, what is that wired to? The Fan Relay or the stock dash mounted Tempeature Gauge?

Does your dash mounted tempeature gauge function? and if so, where on the engine is it wired?

I have to assume that your Fan does not come on automatically?

The switch you refer to that's mounted on your dash - is that an add-on or did it come that way? Is it simply a Toggle switch? Does it work? (or is that the reason for your original Reply)?

I mounted a Toggle switch on my dash so that I could override the system and turn the fan on whenever I wanted and still retained the automatic funtion. I spliced one side of the Toggle to the Green (maybe Green with a White stripe) that runs from the Relay to the Gizmo (I'll stay away from terminology as that may be where some of the confusion is coming) between #6 & #8 and the other side of the Toggle to good Ground.

As I said, my system does funtion properly. If your system does not (hacked wires) you can have manual control by wiring a Toggle, one side to the large Red wire at the Fan itself and the other side to good Ground. I believe the that Red wire is always hot. With the use of a Toggle you should Fuse it.

I just want to add a couple more points. My set-up is quite typical, which means that not all applications are the same. Drivers side between #1 & #3 is a single wire Temperature Sender (also Green) which feeds the F7 pin on the Bulkhead Connector (at the Firewall) that sends a signal to the Tempeature Gauge. The Gizmo (Coolant Temp Sensor or Fan Switch) mounted between #6 & #8 on the pass. side is as I described before.

We should be carefull not to confuse Sensors and Senders, just a terminology thing.

Come on back, if I can help. I sympathize with your 'Hacked Wire' situation. When I installed my old school 383 and removed all CC related wires I had a real mess. BTW, it was this site along with the Electrical foum plus a lot of reading that helped me thru it.

 

pardon my inaccurate jargon. the 'gizmo' that i put in my pass. side head is my temperature sender that goes to the guage (single blade connector). i don't know if the guage works or not yet because the engine still hasnt been started in this car. the toggle switch on the dash is an add-on but like i said i haven't traced the wiring yet and don't know if that's what turned the fan on but i'm 90% sure it did.

when i got the car the fan was out of it, the wires to it were cut, one was blue i think and the other black. in the engine bay there was a blue and black wire that looked out of place that runs from the front of the car to the bulkhead, the ends are cut which leads me to believe the fan was connected to them and that they go to the switch on the dash.

so what i think i can do is put a fan switch in the driver's side head. i'm not sure but does it have two terminals that have continuity between them above the set temp. in it? like 230? if yes then what i want to do is run a hot wire to one terminal and a wire from the other terminal to a relay to kick it on when the switch reaches the set temp. make sense?

i'd go look at the car but it's at my parents' house two hours away. i will see it this weekend though.