Mech. Fan delete/Primary kicking on right away?

So, I finally got around to switching from Mech. Fan. I used Innovative Wiring kit. The kit was a breeze. Took my time to make sure good connections were made. The only piece of the kit I didn't use was the small harness for the primary fan to the secondary fan because the fan I got had a stock one attached. As soon as I started the car, the primary fan kicked on and stayed on. When I unplugged the temp sensor of the water pump, the secondary kicked in. I am thinking the primary fan should not have kicked on right away. Any help out there would be appreciated. She is my daily driver and I need to get her back on the road.

On the up swing, I got my heater core flushed out and I went from little heat to melt your face off heat. also got the oil cooler lines and radiator replaced. This fan thing just has me concerned. Thanks all.

If I'm not mistaken the fan comes on when a certain temperature is reached. Was the car hot or cold? I think you're on the right track with checking the temp sensor. Make sure its the right one. I believe there are two sensors and the one below the driverside head on the block is the one you need, if memory serves me correctly.

Check to see if the fan goes off when you turn the AC off.

The car was cold. I had the heater on 90 degrees. I did notice that the AC compressor was cycling on and off the whole time the car was running. I hadn't noticed that before, but it has been a while since I have been under the hood. I just had the compressor replaced this fall.

It should not be coming on immediately. It should activate at a certain temp. Although I put in dual electric and deleted the mechanical fan, I'm running a Corvette ECM and TPI system that I reprogrammed and cannot advise you further than that.

Sorry, Dave

oldfriendabb wrote:

She is my daily driver and I need to get her back on the road.

I would not be concerned about driving it (assuming it shuts off with the key?) Yes, it is unnecessary but it won't hurt anything to drive it that way while you get things sorted out.

If it does not shut off with the key, then I suspect you wired something incorrectly or got a bad relay. Does your relay have both a "87" (N.0., Normally Open) and an "87a" (N.C., Normally Closed) contacts? If you accidentally connected the fan to the "87a" contact instead of the "87" contact, then the fan will come on with the ignition off, and shut off when the engine warms up.

oldfriendabb wrote:

I did notice that the AC compressor was cycling on and off the whole time the car was running.

That's normal behavior so long as the temperature is above freezing and the CC is not set to "Vent" or "Off".

thanks for all the input guys. Now that the little ones are in bed, I'm heading back out to the garage to check on some things. The fan turns on when the engine starts and turns off when the engine is turned off. I didn't know the AC compressor would cycle like that with the climate control. I would think the temp sensor under the head, but when it is unplugged, both fans kick on as they should per the directions of the wiring kit. So if it was the sensor, I would guess both fans would be on. Not just one. I don't know. I am guessing it is this sensor that then feeds the relay. I am going to go mess around and see if I can come up with anything else. I will keep checking in to see if any one posts any other ideas. Since I was having problems with the mechanical, I am surprised how much quieter the mech. fan is.

My car is factory with tow package. I have noticed my ac compressor still cycles even when it's in the 40s and I have it on 90. Not sure why but heat works so f-it

I think GM has used the AC Compressor for a long time to help the heat/defrost remove moisture from the cycled air. If you have your front defroster vents open it may cause the fan to run with the AC cycling.
One of the Xberts may chime in here. Jeff

If the defrost is on, the a/c compressor will engage so you have warm DRY heat blowing on the glass. When the a/c compressor comes on, one of the fans will come on too.

I did the mechanical to electric fan swap too this past summer. I love how much room it opens up under the hood....but don't love how it works. I used the Innovative Wiring kit too. With the a/c on, it works fine. One fan runs, and in the heat of the Texas summer, the other fan will click on and off as needed. When the a/c is on, the temp gauge never goes over halfway (and it never even got to halfway with the mechanical fan setup).

What I'm told is normal, but I don't like, is now with the temps in the 70's here for the next five months, I like to ride with the windows down and the a/c off. Well the fans do not kick in until the temp gauge is almost at the red mark on the gauge. I hate this, but am told it's normal. When they do kick on the cars cools right down, but I don't like watching the gauge climb at lights or in traffic, and more often than not kick the a/c on rather than letting the car get that hot.

I'm looking around to find someone locally that can hopefully re-program the computer to kick the fan on at a lower temp. For now, I just use the a/c when it's not needed....

-Mike

Update: Outside temps in the 20s-30s here today. I went out last night and after reading some of the posts, checked and figured out that if I turned the climate control off the primary fan would kick off as well. At that point it would cycle on and off as Mike describes. I don't like watching it climb either Mike. Climate Control on (fan on) the temp doesn't reach halfway. Climate Control off(fan off) it goes 3/4 of guage before kicking in and then kicks off at half way.

then came my next surprise. I was sitting idling with the climate control on and realized my guage was at 3/4 (almost red). I hopped out and popped the hood. The fan was off and kicked on shortly after I popped the hood. So now, apparently the primary fan is not running with the heat on. I give up.

What I haven't seen yet is the secondary fan kick on at all. ?

I can definitely hear the exhaust note a lot better now.

81X11 wrote:

If the defrost is on, the a/c compressor will engage so you have warm DRY heat blowing on the glass.    When the a/c compressor comes on, one of the fans will come on too.

I did the mechanical to electric fan swap too this past summer.    I love how much room it opens up under the hood....but don't love how it works.    I used the Innovative Wiring kit too.    With the a/c on, it works fine.   One fan runs, and in the heat of the Texas summer, the other fan will click on and off as needed.   When the a/c is on, the temp gauge never goes over halfway (and it never even got to halfway with the mechanical fan setup).

What I'm told is normal, but I don't like, is now with the temps in the 70's here for the next five months, I like to ride with the windows down and the a/c off.   Well the fans do not kick in until the temp gauge is almost at the red mark on the gauge.  I hate this, but am told it's normal.   When they do kick on the cars cools right down, but I don't like watching the gauge climb at lights or in traffic, and more often than not kick the a/c on rather than letting the car get that hot.

I'm looking around to find someone locally that can hopefully re-program the computer to kick the fan on at a lower temp.   For now, I just use the a/c when it's not needed....

-Mike

I had to do some checking first (a practice quite a members have been neglecting before blazing away at the keyboard attempting to answer tech questions lately, but that's an issue for another day) but with the help of a friend it appears this is what is happening:

When an LT1 car is equipped with the mechanical fan, then the factory program disabled the flag for the primary fan not running.

(The PCM is expecting to see the resistance for the primary fan relay, which wouldn't be available.)

And the coolant fan turn-on temps are still enabled in the program, but they are raised beyond what would be normally programmed for a dual electric fan setup.

(Somewhere in the area of 10 degrees C higher, if his recollection was correct.)

Which is to say that the fans will work pretty much as you are seeing.

Since we usually (read: never) performed a fan swap w/o reprogramming the PCM at the same time, it wasn't a behavior we had seen in our cars.

So to complete the conversion, a PCM update is needed to take full advantage of the new fan configuration, and it would be a good idea to re-enable the primary fan warning flag while you are in there.

- J

Thanks for the input J. Anyone have any guidance on what kind of shops can do such reprogramming? I am going to have to get it done. I can't keep watching the temps rise that high.

Junkyard -> spare PCM -> PCMforless mail order tune.

I did this exact swap with the Innovative harness. With the A/C off I do not see this fan-on behavior, and I started with a tow-pack car as well. I've yet to see the secondary fan kick in except when the A/C is on or if I pull the plug on the temp sensor.

When I get a chance I intend to lower the fan-on switch points as well, but so far what I've seen matches the behavior described here and is by design with regard to when the primary fan comes on.

The temp sensor on the head only controls the gauge in the dash. The one on the water pump is the one that controls the fans.