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

 

[RD_Atlanta]

I was able to come up with a solution to stopping the AC compressor from turning on below a certain temperature on the 00-05 LeSabre's with the automatic climate controller. There is an obscure setting in the 00-05 LeSabre PCMs to address this. However, I was disappointed to find that the 00-03 PCM (Serv Nbr 12583826) has an issue with this logic, in that the logic is reversed (temperatures below the setting, the compressor is enabled). Interestingly enough, the 04-05 PCM (Serv Nbr 12583827), this logic works correctly. I chose to install the 04-05 PCM in my 03 LeSabe. I went through all of the code and I/O and the only circuit that seems to have changed between the (2) vintages of PCMs is the O2 sensors circuit. The field wiring did not change but the operating limits of the O2 sensor and the O2 heater resistances changed. I chose to keep the original 2003 O2 sensors and moved the calibration for the O2 sensors to the 04-05 Ser. Nbr. 12583827 PCM. Besides having to address the differences in the O2 operating ranges, the Serv Nbr 12583827 PCM seems to work well.

So, I currently have the setpoint at 40 deg f and when the outside air is below 40 deg f, the AC compressor is disabled and I'm not required to press the vent button. Its just unfortunate that the earlier (Serv Nbr 12583826) PCMs had something wrong in the logic that reversed the behavior. For LeSabre owners who are not deep into working with the PCMs, I would not recommend making such a modification. Otherwise, it appears the vent button is probably the most practical daily work-around.

 

[2000ltd]

I was able to come up with a solution to stopping the AC compressor from turning on below a certain temperature on the 00-05 LeSabre's with the automatic climate controller. There is an obscure setting in the 00-05 LeSabre PCMs to address this. However, I was disappointed to find that the 00-03 PCM (Serv Nbr 12583826) has an issue with this logic, in that the logic is reversed (temperatures below the setting, the compressor is enabled). Interestingly enough, the 04-05 PCM (Serv Nbr 12583827), this logic works correctly. I chose to install the 04-05 PCM in my 03 LeSabe. I went through all of the code and I/O and the only circuit that seems to have changed between the (2) vintages of PCMs is the O2 sensors circuit. The field wiring did not change but the operating limits of the O2 sensor and the O2 heater resistances changed. I chose to keep the original 2003 O2 sensors and moved the calibration for the O2 sensors to the 04-05 Ser. Nbr. 12583827 PCM. Besides having to address the differences in the O2 operating ranges, the Serv Nbr 12583827 PCM seems to work well.

So, I currently have the setpoint at 40 deg f and when the outside air is below 40 deg f, the AC compressor is disabled and I'm not required to press the vent button. Its just unfortunate that the earlier (Serv Nbr 12583826) PCMs had something wrong in the logic that reversed the behavior. For LeSabre owners who are not deep into working with the PCMs, I would not recommend making such a modification. Otherwise, it appears the vent button is probably the most practical daily work-around.

I'm glad you've got that fixed.

 

[02LTD2.0]

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

If your temperature dropped to 135° F you should check to see if you have a thermostat that is either missing or stuck open. I had a 2001 Limited that had a Fail-Safe thermostat that was stuck in the open position. I replaced it with a regular 195° thermostat and it operated properly after that.