Got this Vette a few weeks ago and need to verify my temp readings. It seemed to be running hot when I got it (215* normal operating and 230* max by the digital guage and "oh crap" hot by the analog) so I went through the cooling system and put in new temp sensors in the block and water pump, replaced the water pump and T-stat (not sure what happened to the sealed bearing but the bearings were visible around the shaft and it had signs of leaking), replaced all the hoses and cleaned/straightened the radiator fins. Car now runs at 190* on the road and maxes out at 230* in stop and go traffic. I have a GM service manual that says the fans are supposed to come on at 219* for low speed and 228* for high speed. However, low comes on at 228* and I never get hot enought to get high speed operation. I have read on this forum that low speed is supposed to come on at 228*.

Question: is low speed operation supposed to kick in at 228* like I see or 219* as the FSM states?

 

As the Manual states!!

What year car?

You might be mis-taken the 217/219° low speed operation if you have an LT car. The fans are very quit and move a small amount of air..high speed operation at 228° moves alot of air.

 

Sorry! Updated my sig after I posted. It's a 96 LT1 with Auto Trans. I connected my scan tool (Auto Xray 7000) and the low speed is being commanded on at 228*. I can watch the fans come on when commanded and go off when the signal is removed. My car is an early 96 actually manufactured in Aug 1995.

 

Your low speed fan operation doesn't sound right. It's time to hit the FSM

 

What should I hit it with? Just kidding. The relays all work and the fans turn on when commanded by the ECM. I can watch the FAN #1 RELAY and the FAN 2&3 RELAY status on the Scan Tool and the fans follow as expected. My problem is that the ECM is commanding them on at different temps than what the FSM states.

Does anyone have an FSM for 1995 Vettes? What are the fan turn on temps stated in it?

 

The fan should be going on at 228, the secondary fan goes on when the a/c is turned on. I have my relays grounded to have them both go on at 228 so it cools down faster.

 

Stopped by the dealer today and had the service department look up the temps for activation on 95 and 96. They are both 219* for low speed and 235* for high speed. Now, why don't they work that way? I've seen quite a few posts through searches that say 228* for first fan activation.

Maybe I should call it good since it never gets above 230* even sitting in th garage at idle for 30 minutes...

 

Why not get the ECM reprogrammed to on at 207* off at 197* like many have the '96 operating? There are other things you can do as well that make it very worthwhile. Call or Google PCMFORLESS. Great results for mine in performance, shifts, 93 octane fuel trims and the cooling fan characteristics. The '96 fans both come on low for cooling. They both come on high when the AC is on.
I watch it go up and down in traffic. Never above 208*. The higher temp settings were to decrease emissions at the expense of everything baking inside the zero circulation engine bay.

 

That's what I'm looking to do now. I'll probably opt for something so I can tune it myself though.

 

Hi mwzeigler,

As you have a 96 (same for 95), you have 3 fan relays (unlike my 94 and earlier), so your fans operate together -- slow speed at 228 (or AC @ 189 psi) and high speed at 235 (or AC @ 225 psi). That 3rd relay controls the fan electric flow -- fans are in series for slow-speed, and in parallel for high-speed.

Unfortunately, the dealer and the FSM (likely what the dealer is looking at too) are incorrect and GM never released a TSB to correct, or somewhere in the past, GM released a 'flash update' to the LT1 ECM which caused the LT1s to operate at the LT4 temps instead (not sure if intentional or incorrect).

Suggest reviewing FSM book 2, (VIN J) 6E3-C12-1, contrasted to (VIN P) 6E3-C12-1, where the different temperatures are presented.

Also remember a correctly charged AC system is important to proper coolant fan operations as AC head-pressure plays into the fan operations (as noted above).

Generally, given 70 degree temps outside, when you turn on the AC, both fans should come on at low speed. If really hot outside, or after running for a bit, both fans may speed-up to their high-speed setting.

Hence why many of us run the AC all the time, actually keeps the engine cooler, especially at traffic lights.

btw, your temps now seem pretty good, so assuming AC fan operation is working correctly, you should be able to rest easy...

 

I pulled my 95 FSM; 6B-6

Imputs that effect fan operation,

-A/C Condensor pressure.
-Coolant Temperature.
-Oil Temperature.
-Throttle position.
-Vehicle speed.
-Engine speed.
-PCM Status.

FSM; 6E3-C12-4

Relay #1 (LOW Speed)
PCM A11 CKT 335 (DARK GREEN) PCM provides a ground for turn "ON"

Relay #2&3 (High Speed)
PCM A10 CKT 473 (Dark Blue) PCM provide a ground for turn "ON"

Low "ON" 226f "OFF" 221f
High "ON" 235f "OFF" 230f

Both Realys are provide Voltage with "IGN" On

My Scanner is broke, but if needed I can Scan at a later date and send...just send a PM.

mike

 

theadmiral94 - I agree that GM overlooked a change that should have been made to the FSM. Fans work fine with AC operation with cool and hot temperatures. It was over 100 degrees when I started looking at it but it's in teh 60's now. Gotta love North Texas weather! I am pretty happy with the temps except the large swing between highway temps and in-town driving temps. I will get a programmer later to change the fan turn on temps.

DesertMike1 - Thanks for looking a the 95 FSM. Different than the 96 AND different than what the dealer stated for 95. I even looked over his shoulder to make sure he looked up the correct info for the correct years. 95 and 96 were the same (219* on for slow speed and 235 on for high speed).

I'm happy for now. Going to drive it while the weather is still enjoyable! Thanks to all for the assistance.

Mike