I've been searching, but I am NOT having any luck. I have a Ruby Red ('93) coupe 6 speed LT1 BONE STOCK. I understand that there is a fan switch on the market that replaces the stock 237* switch on the right head behind the oil dipstick, and kicks the fans on at abot 200* or so, and off at 180*, or something more reasonable than the almost 240* switch that it now has. Anyone know the Part # or what to look up at a parts store to get it?

THANKS!!

 

bump...I'm looking for one too. I haven't tried NAPA yet, but I heard they may have them

 

http://www.madvet.com/shop?frame=3.138.944

 

I'm not familiar with the fan switch setup on the LTx engines,
but on the L98, the fan switch for the Auxiliary fan is on the
driver's side in the head above & between #1 & #3 plugs. I
believe the item in the #6-#8 location on the passenger side
of the L98 is the sender for the instrument gauge and ECM.

If the fan switch for the LTx is the same as the L98, then I
posted a list of part numbers for Echlin fan switches that are
available through NAPA and maybe sold by others.

To find the listing, use the 'Click for Advanced Search' option
you'll see in the dialog that appears when you click Search.
Enter 'fan switch' as key words. Be sure to narrow the search
to 'C4 Tech'. You could add 'Slalom4me' in the name field. If
you click the 'Posts' check box, then the results will show specific
posts containing the key words 'fan' and 'switch'.

I created a post yesterday that has a link to the original post.
You'll see this post in a thread about a C3 fan conversion.

There are four different part numbers along with the operating
temps of the switches in the original post.

Hope this helps.

.

 

I found your thread a few months ago and used the info you posted to cross over to a brand my local jobber sells. You can add Niehoff to the list.
Oh, turns out Niehoff is owned by NAPA

 

Keep looking. The fan switch is in the right head for the 1984 and 1985 cars. For the 1984 it controls the only fan. On the 1985s, it controls the aux fan in cars so equipped or serves as a back up to the ECM for cars with only the main (single) fan. In 1986 through 1989, the AUXILIARY fan switch moved to the left side of the car to between the #1 and #3 spark plugs. The main fan is operated by the ECM (only) those three years. In 1990 the fan operation, both main and auxiliary, was assumed by the ECM. No more thermal fan switches after 1989. To change the on/off temps of a main fan after 1985 takes a program change in the prom, or a revision to the factory wiring. The same is true of BOTH fans from 1990 and up. I am quite sure of 1990 being the year the ECM first took over control of both fans. In any case there are no factory fan switches for a 1993, not even for a "Ruby Red". If 1990 wasn't the year I (we all) WILL hear about it.

Although your car doesn't have a fan switch that can be changed, your fan on/off temps COULD be altered with the addition of a switch or two and some rewiring. However, reprogramming is much more sanitary and civilized.

RACE ON!!!

 

The ECM controls fan operation based on input from the coolant temp sensor. When it sees a certain value, it enegizes the appropriate fan relay. When the temps lower to the value reported by the sensor, the ECM shuts off the relay.

The coolant temp sensor that feeds the ECM is at the lower front of the water pump. The sensor on the driver's side cylinder head is used for the water temp gauge.

You didn't mention what the coolant temps are that your are seing. For a later C4 with a factory thermostat, 190-205 degrees are pretty normal. IF the ambient air temps get high or you do a lot of city stop-and-go driving, the temps will climb higher until the secondary fan kicks in at 228 degrees or so. Once the coolant temps drop, the secondary fan will shut off. Running the A/C automatically turns the secondary fan on.

If you are seeing coolant temps in the 230 range, I would be looking for problems in the cooling system. One common problem with C4 cooling is debris clogging the radiator. These cars are "bottom breathers" and you can get a lot of junk collected in the front of the A/C condensor and the radiator.

You can use a shop vac to suck out the big chunks or direct a stream of water from a hose fromt he back side of the radiator.

IF the coolant is dirty looking, it might be time for a complete flush and refill. It would also be a good time to change the upper and lower radiator hoses.

 

with CFI-EFI, you need to have a chip reprogammed for the computer.

 

THANKS!! Good info!! You were right about the debris in front of the radiator. I took the shop vac to it and that seemed to help. As far as teps, I was seeing it get as high as 240*. That was a bit spooky, so I started doing some homework, and found out that, supposedly, the switch on the right side head is the one that kicks the fans on at around 230*. My theory was to get a switch that will do it a little sooner, and kick them on before the ECM does, since that switch (on the pass head) kicks both fans on.

Since the debris removal, new thermostat, and coolant flush has seemed to help, I'll probably leave well enough alone. With it being an anniversary car, I dont want to mod it ANY more than I have to.

THANKS AGAIN!!!

 

Where did you get the info for your "homework"? c4cruiser and CFI-EFI aren't jerking you, they're giving you correct information. Try this for homework, disconnect the connector from that "switch" as you call it on the pass head (should be a single Dark Green wire) and see what happens with ignition on. Do either of the fans come on or does the guage go to cold. Then touch this green wire to ground. Do either of the fans come on or does the guage go to hot. I think you'll find that you'll only affect the guage. If you insist on changing things without a reprogram, as CFI-EFI said, "your fan on/off temps COULD be altered with the addition of a switch or two and some rewiring.". In your driver head, forward, between cylinders 1 and 3, you should find a pipe plug. This can be removed and a Switch installed. It could then be wired to either or both fan relays. Wire into the Dark Green/White trace wire for the Primary Fan and/or the Dark Blue/White trace wire for the Secondary Fan.

If it were me I'd do as you said and leave well enough alone. You don't want to be dicking with wiring on an Anniversary car, but the info is there if you're willing to believe or at least prove it to youself.

 

I don't doubt ANY of you one bit. I got most of my info from the Haynes manual, but I've known them, more than once, to be incorrect, which is the very reason I posted here. I trust you guys more than Haynes.

Actually, the manual said that the switch on the pass head behind the dipstick was to turn both fans on at about 238*. I was thinking if I replaced that switch with one that came on at 210* or so, then problem solved. No rewiring, toggle switches, etc. However, I removed some debris from the front of the radiator, gave the cooling system a GOOD cleaning, installed a new thermostat, and replaced the relay for the secondary fan. Still not the super cool cooling system I was wanting, but a thousand percent better than it was. Works as good as it did from the factory, so I think I'll leave well enough alone. Just wanted to make sure it was good for the Cruise-in at the Corvette Museum on Memorial Day weekend. My wife is about to jump out of her skin in fear that it won't be ready, but I feel pretty good about it now.

Hope to see you all there. If you see a Ruby Red Vette with polished ZR1 wheels and Hamblen county Tennessee tags, PLEASE, come up and say "Hi".

 

The "switch" does not operate the fans directly. It is simply a sensor that the ECM uses to determine when to send a ground signal to the fan relay. The ECM programming is set to turn the secondary fan on at a specific value from that sensor which IIRC, is a specfic resistance in Ohm's.

The only real way to change when the fans come on with the LT1/LT4 cars is with a aftermarket chip or programmer. While the typical operating temps of the later C4's seem high, they run that way for control of exhaust emissions. Changing the operating temps to a lower value may provide more peace of mind, but can cause increases in emissions, and that can lead to failing a sniffer test if your state requires one.

We get to see the temp display in both a digital display and an analog gauge. Many other cars run this hot but most cars don't have anything but an analog gauge so there is no real accurate way for a driver to determine if the temps are just right or too hot.

As far as the Haynes manual, toss it out in the trash or use it to wipe up oil off the garage floor. Get the real GM Service Manuals from Helms. You can order them from www.helminc.com and you will have the same set of books that a GM service tech uses at a dealership. Best $120 mod you can do!!

 

I have an '84, and there is a switch for the fan between the #6 and #8 cylinders behind the dipstick tube. There's a green wire going to it, and when grounded, the fan does come on (with the key on).

There's a sensor between #1 and #3 on the drivers side, and when the wire is disconnedted the temp guage reads cold, and when shorted reads hot.

Now for my problem. I bought the cool-temp kit from mid-america, and the switch doesn't fit in my head. The problem is that the part that is supposed to go inside the head has too great a diameter, so it will not 'thread' in. Has anyone heard of this happening?

I'm now concerned that my heads and/or engine are not OE, but thought I'd check before pulling my valve-covers to find the casting numbers.

thanks in advance!

 

Is the old and new switch the same, i.e are you replacing the correct switch?

 

Well, I'm trying to put the new switch into the same location, but the switches are certainly different. They both have similar connectors on the electrical end (actually the old one is heat-damaged which is why I first decided to replace it with a lower-temp one).

However, they are significantly different on the side that goes into the head. The new one (http://www.madvet.com/shop?frame=1.138.944) has the brass with the same diameter as the rest of the shaft where the threads are, but the old one (that I took out, and ended up putting back in) goes to a much smaller diameter (~1/2) and looks more like this one (http://www.madvet.com/shop?frame=1.3216). I know that's an 02 sensor, but that's more like what my switch looks like on the inside engine part.

 

If you make your secondary fan come on before the primary...

It will come on at all vehicle speeds, and actually hurt airflow on the freeway (maybe hurt the fan too).

It doesn't work nearly as good as the big fan, and is kind of a waste to use it instead of the more effective one.