Cooling Fan Relays: Porsche VS GM

I currently am using the original Porsche cooling fan sensor in the radiator and stock cooling fan relay system in my vehicle. I have the TPC large capacity radiator with the stock Porsche cooling fans. Recently I have noticed that the fans will only run on low speed and I am having some cooling issues at slow vehicle speeds. I need to address this problem and I have to decide to fix the original Porsche system or to change it to the GM system using the LS PCM and three relays. I have not diagnosed anything yet but I know that the wiring to the cooling fan resistor is petrified and needs replacement. If the Porsche cooling fan relay is bad, it would be cheaper to switch to the GM three relay system because the Porsche cooling fan relays are very expensive if you can still get them. If I keep the original Porsche cooling fan control system intact, my A/C fan and compressor control will still work. If I switch to the GM fan control system, how can I get the fans to work when the A/C is on? What is the best route to take? Thanks, Gil

I do not run ac, so i cannot assist you in that department, but i did ditch the Porsche sensor, relay etc and built a 3 relay box controlled by the gm ecm. Cost me like 30 bucks for the relays and a dedicated fuse panel/ relay box on amazon. With hp tuners i can control my high/low speed fan operation.

Thanks for the response. I believe there is an advantage with the GM setup because you can select when the fans turn on and off. I need to know if and how they can be incorporated into the A/C system for the fans or if the GM computer can be used to control the A/C compressor as well.

Top picture is to run both fans at the same time. That's my preference.

Bottom picture will run one fan at low temp, and then both fans at higher temp.

Both have the 3rd relay for the A/C to activate the fans.




I also will use the Porsche system to control the fans. It works perfectly fine. And there is a new solid state relay that virtually eliminates failure.

https://www.ftech9.com/new-products/solid-state-fan-relay-944-amp-968-1

Thanks for the information. I need to look into my fan control system to find out exactly why I only have low speed right now and then decide what route to take. I believe that there was a post in the past that said you can use the GM PCM to control the fans through the stock Porsche relay by wiring it in where the radiator sensor is located. If I get the new solid state fan unit and use the GM PCM to control it, that might be the best way to do it.

Yeah, like hotrodz said, the solid state relay is an option. I looked at that initially. Depends on how much you want to spend. I choose the cheap diy route. And if the relays fail, it costs me a couple bucks to replace. That and I wanted more control over my fans.