New Guy has a Q oubout the fan

[bad89vet]

I was just wondering at what temp the electric fan came on at i have 1989 and the temp goes up to about 215 and the fan still does not come on thanks for the help.

 

[86Vette1]

Glad you asked - I have the same questions about my 86. Temp was over 208 F and fan still hadn't some on. Doesn't seem right. I went throught the Haynes manual diagnostic, but that led to as much confusion as help. My fan motor is OK. The relay is OK when I bench test it, but if I disconnect the temp "switch" on the rear of the right cyl head (per Haynes) and ground the lead, the fan does not come on. Which leads to my confusion...is this the temp switch or the temp sensor? When I disconnect it, the dash readout says "LOW". When the lead is grounded, the dash reads "299F" (obviously max range). With the lead connected, I get a true reading. And no affect on fan operation. I'm sure this is the temp sensor for the dash reading, not the fan switch. So, where is the fan switch? Is it the 2 wire sensor at the front of the intake, right below the small coolant line? What is the sensor just to the right of that, which is another 2 wire sensor but with larger, rectangle connector. Is that the "Cold start thermal time switch"?

And on the topic, the Haynes is more confusing about sensors than it is help! Anyone know a good on-line resource? I can't figure out the oil sensors either...2 or 3? And what is the "N5 Engine Temp Senor (gage overheat)" supposedly located at the left front side of the engine??

Help...I'm lost!

Thanks.

 

[MBDiagMan]

If it's the same as the '88, it has a coolant fan and an auxilliary fan. The coolant fan is activated by a temperature switch that turns on when the coolant temperature in the engine reaches 228 degrees Fahrenheit. The auxilliary fan whose purpose is to bring down dangerous high side a/c pressure turns on when the high side pressure reaches 240 PSI and then turns off once the high side pressure goes below 190 PSI.

This means that the cooling system relies on ram air most of the time. I wouldn't get wrapped around the axle just because the fans don't run most of the time. If the cooling system is in good shape and the pressure cap is holding specified pressure, coolant will not boil until around 245 degrees or so.

Have a great day,

 

[86Vette1]

Man, it seems that waiting until the coolant temp is over 225 F before turning on the fan is way to high! Why would GM want to let the coolant get that hot? On my 86, the thermostat is a 195 F, so I would expect thte target coolant temp is about 195. Yet, they wait until > 225 to turn on the fan. I would have given the fan setting about 10 deg above the thermostat, with about 15 deg deadband to turn off.

What do you guys think? Anyone added a second fan and/or second relay/temp switch to run the OE fan at a lower setpoint? I'm thinking about doing that.

By the way, mine does not have the Heavy Duty Cooling option, with 2nd fan.

 

[Top]

228 was/is how Chevy got the engine hot enough to pass emissions tests. Easy fix is to install a manual switch and turn the fan on when you want. I turn mine on at 200. In the summer here, with the AC on I turn on both fans at 200. You can also spend more money on sensors, reprogamming, etc if you want, but the 12.00 manual switch works best for me.

Good Luck

 

[Daryllawman]

I run my fan all the time........it never gets above 195, even in traffic.....

 

[Edmond]

I did a chip that turns the fans on a 188 and I run two bottles of Water Wetter. I got the chip from Jeff here on the forum and he also did a few other tweaks. Shoot him an e-mail to get some more info.

 

[86Vette1]

Ah ha! I knew it. It's the old emissions conspiracy thing! Thanks for the great input. I really appreciate it. I will definitely be changing the coolong system.


Have a good summer all. Great site!!

 

[MBDiagMan]

I live in Texas and have run mine in really bad stop and go traffic jams on days with an outside temperature of 108 degrees with absolutely no problems. Although the GM engineers often have their heads "where the sun don't shine," they have this right. The 228 is measured at the cylinder head where the temp is at its highest.

Additionally an engine will last longer if the coolant temperature is as high as you can get it without the coolant boiling. This is evidenced by micing the cylinders at overhaul time. The end cylinders that run cooler will always have more wear than the interior cylinders that run hotter.

If you keep everything in good shape, the cooling system and fan settings as designed will be optimum.

Now one thing to consider is that evidently some cars don't have the aux fan. I get this impression from the service manual although I haven't seen a car without it. I expect that this could be because I'm in Texas.

If you are in a hot climate where you don't have a second fan, or have a car from a cool climate that has moved to the heat of the South, then adding the aux fan would be a good idea, but stay with the factory designed temp settings.

Good luck,

 

[olefam]

How is it that so many of you folks know the exact temperatures of your oil and engine coolant? My 1991 coupe has guages, but they read from 100 degrees to 260 degrees in a simple curving line. My needle rests "somewhere" in the first 1/3 of the arc. What am I supposed to do - guess what temperature that corresponds to? Same for my oil temperature. It actually seems to read cooler than my engine coolant. But it could be because the oil temperature guage goes up to 320 degrees, thus if the two temperatures were identical, the needle would rest "lower" in the arc, appearing to be cooler than the coolant guage. Any help or advice would be appreciated.
Glen

 

[Edmond]

How is it that so many of you folks know the exact temperatures of your oil and engine coolant? My 1991 coupe has guages, but they read from 100 degrees to 260 degrees in a simple curving line. My needle rests "somewhere" in the first 1/3 of the arc. What am I supposed to do - guess what temperature that corresponds to? Same for my oil temperature. It actually seems to read cooler than my engine coolant. But it could be because the oil temperature guage goes up to 320 degrees, thus if the two temperatures were identical, the needle would rest "lower" in the arc, appearing to be cooler than the coolant guage. Any help or advice would be appreciated.
Glen

Hi Glen, welcome to the Corvette Action Center.

We all know our temperatures because we're that darned good! :L Seriously though, we have digital dashes. I think 1990 was the last year of the digital dash.

 

[86Vette1]

MBDiagMan - Thanks for the reply. Can't say I agree 100% with the notion that engine wear is reduced by running hotter. First time I ever heard such a theory. Generally, cooler is better as long as things like minimum oil viscosity and condensation issues are not a problem. In fact, I believe one of the elegent design improvements in the LT1 was the reverse cooling, where the coolant goes to the head first, then the block, which results in cooler running combustion chambers and the ability to make more power without detonation.

My '86 just has the single fan, but it looks like even those of you with the Option HD cooling option (ie aux fan) have the same setpoints.

I gotta believe that the comments "Top" made about making emission limits are a big part of the reason the designers allow the temp to go so high before turning on the fan.

Just my opinion, though.

 

[MBDiagMan]

I think you're not paying attention to the evidence. Did you not read my findings about micing end cylinders vs. cylinders with partners on both sides? This is fact, not fiction or theory.

Have a great day,