2000 Limited Cooling fans both come on when I turn heat on

[2000ltd]

I was doing a coolant flush today and doing that I found out that both fans come on as soon as I turn the heat on. It's obvious what the downside of that is so if anyone knows how this happens or how to fix it please let me know. I'm lucky to live in florida but still when it comes time to turn on the heat I'd like it to work

 

[DrivenDaily]

When you turn on the heat, press the "Vent" button and it will turn off the AC, which will turn off the radiator fans. You will still get heat, but without any dehumidification.

It does not hurt to use AC with heat since it helps keep the windows from fogging up in humid weather. And since you're in FL, you know what humidity is!

 

[2000ltd]

When you turn on the heat, press the "Vent" button and it will turn off the AC, which will turn off the radiator fans. You will still get heat, but without any dehumidification.

It does not hurt to use AC with heat since it helps keep the windows from fogging up in humid weather. And since you're in FL, you know what humidity is!

I thought it would cool the engine so much the heat wouldn't work. I'll definitely do the vent thing if the heat doesn't work. When I was doing the cooling system flush I brought the car up to 189° F and turned on the heater on full according to directions. That quickly brought the coolant temp down to 135° F

 

[DrivenDaily]

When following directions to engage the heat fully, it's more for the sake of any vehicle with a valve that shuts off the coolant flow to the heater core. Otherwise, the coolant flows through it continuously and therefore does not need to be on high, low, or even on for that matter.

 

[2000ltd]

Does the 2000 lesabre need the heat on to do a coolant flush?

 

[RD_Atlanta]

On my Limited LeSabre, I'm also addressing the issue with the vent button. The problem that I've had with this logic is that when it's 15 degrees F outside, all I desire is as much heat as I can get into the cabin and as quickly as possible. I think in these conditions, being forced to either run the AC compressor (Recirc mode) or to pull in cold outside air (vent mode) is a flawed design (a problem that does not exist on my Lesabre's with the manual climate controller). This logic resides in the Instrument Panel Integrated Module (IPIM). I was glad to see this post because it reminded me of this issue. I personally would like to come up with a simple elegant solution which last winter I was not successful.

There are provisions in the PCM program to send commands to disable the AC from being called (over the Class-2 bus to the IPIM) but none of the logic will address this particular scenario. I haven't yet seen a viable hardware switch solution to block the AC compressor and cooling fans because we would not want to disable the cooling fans if they were needed (even in very cold weather).


While I like the 00-05 LeSabre's, I'm sometimes frustrated with the distributed controls. I'm OK with a distributed architecture, it sometimes seems difficult to follow. I hope over the winter to gain a better understanding of the architecture and which module is responsible for what. Perhaps if I can gain a better understanding, it won't appear so fragmented.

 

[DrivenDaily]

On my Limited LeSabre, I'm also addressing the issue with the vent button. The problem that I've had with this logic is that when it's 15 degrees F outside, all I desire is as much heat as I can get into the cabin and as quickly as possible. I think in these conditions, being forced to either run the AC compressor (Recirc mode) or to pull in cold outside air (vent mode) is a flawed design (a problem that does not exist on my Lesabre's with the manual climate controller). This logic resides in the Instrument Panel Integrated Module (IPIM). I was glad to see this post because it reminded me of this issue. I personally would like to come up with a simple elegant solution which last winter I was not successful.

There are provisions in the PCM program to send commands to disable the AC from being called (over the Class-2 bus to the IPIM) but none of the logic will address this particular scenario. I haven't yet seen a viable hardware switch solution to block the AC compressor and cooling fans because we would not want to disable the cooling fans if they were needed (even in very cold weather).


While I like the 00-05 LeSabre's, I'm sometimes frustrated with the distributed controls. I'm OK with a distributed architecture, it sometimes seems difficult to follow. I hope over the winter to gain a better understanding of the architecture and which module is responsible for what. Perhaps if I can gain a better understanding, it won't appear so fragmented.

I have had the same thought about a simple switch that would deactivate the AC and its command of the radiator fans, but still allow the fans to turn on if commanded by the ECM due to coolant temps.

I will check what diagrams I have and see what I can dream up. Doing electrical mods is something I've been doing for some time. Most recently, I modified my 2011 Malibu and the 2 before it to work how I wanted them to work instead of how the programming forced them to work.

The only thing I don't know is whether interrupting the AC and fan signals when disabling AC will cause the MIL to light up.

 

[2000ltd]

I have had the same thought about a simple switch that would deactivate the AC and its command of the radiator fans, but still allow the fans to turn on if commanded by the ECM due to coolant temps.

I will check what diagrams I have and see what I can dream up. Doing electrical mods is something I've been doing for some time. Most recently, I modified my 2011 Malibu and the 2 before it to work how I wanted them to work instead of how the programming forced them to work.

The only thing I don't know is whether interrupting the AC and fan signals when disabling AC will cause the MIL to light up.

Please post an update to this thread if you are able to find a solution to this. I don't want my fans on when I turn the heat on unless it's needed for the coolant temp

 

[02LTD2.0]

To the best of my knowledge the cooling fans are only forced on when the AC compressor is on. Below a certain temperature (maybe 15 or 20 degrees) the compressor will not engage. I may be wrong about the minimum temperature so I'll check the owners manual the next time I go for a drive.

 

[2000ltd]

I have had the same thought about a simple switch that would deactivate the AC and its command of the radiator fans, but still allow the fans to turn on if commanded by the ECM due to coolant temps.

I will check what diagrams I have and see what I can dream up. Doing electrical mods is something I've been doing for some time. Most recently, I modified my 2011 Malibu and the 2 before it to work how I wanted them to work instead of how the programming forced them to work.

The only thing I don't know is whether interrupting the AC and fan signals when disabling AC will cause the MIL to light up.

Please post an update to this thread if you are able to find a solution to this. I don't want my fans on when I turn the heat on unless it's needed for the coolant tem

To the best of my knowledge the cooling fans are only forced on when the AC compressor is on. Below a certain temperature (maybe 15 or 20 degrees) the compressor will not engage. I may be wrong about the minimum temperature so I'll check the owners manual the next time I go for a drive.

Degrees C or F?

 

[2000ltd]

To the best of my knowledge the cooling fans are only forced on when the AC compressor is on. Below a certain temperature (maybe 15 or 20 degrees) the compressor will not engage. I may be wrong about the minimum temperature so I'll check the owners manual the next time I go for a drive.

I googled it. It's 39° F