Cooling Fans / Ballast Resistors/ Fan Hacks/ New Coolant /HOT

My 99 C2's radiator cooling fans do not come on until the climate control hack shows 103C/218F plus or minus a bit. I verified that the fans do work on low speed by turning on the A/C when the coolant temp is below 206F, they come on just fine. Without A/C on the fans come on low speed only when the coolant temp is 218F. I found a hack to add a jumper wire from the low speed relay to the high speed relay for both left and right sides so when the low speed relay triggers it automatically turn on the high speed fan on instead of the low speed. It works like a charm. I also added a switch under the dash to manually turn on the high speed fans at will. Now that you understand what I did can you help me determine if something is wrong. I read that if the ballast resistors on the cooling fan are not working the low speed fans will not come on when the A/C is turned on if the coolant temp is below 106F. Mine did come on so I don't think that is the problem. I also read that the low speed fans should come on without A/C on as soon as the coolant temp hits 206F, NOT HAPPENING ON MY 996. My fans come on (with AC off) when the temp gauge is past the zero in 180 and when the climate control hack shows 103C/218F. I did the hack so low speed is now high speed and the car cools really fast, the fans shut off at 99C thats 210F. I can turn on the high speed fans any time by using the switch - it keeps the needle on the temp right between the 8 and the 0. The coolant was flushed last summer 4K miles ago, its not that and the recovery tank is full. I took the bumper off cleaned out the radiators and in between the condenser and the radiators, its not that. WHAT IS WRONG? IS SOMETHING WRONG OR AM I WORRIED ABOUT NOTHING? THANKS IN ADVANCE! *** Rob ***

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My info is the fans should come on low speed when the coolant reaches 212F degs. They switch to high if the coolant temp climbs to 216F. Regardless of the speed they are running at, the fans shut off when the coolant temp drops to 205F. Based on what you posted, I believe one or both of the radiator resistors is toast and the bad one(s) should be replaced. Before you customize/modify any system in the car the system you are attempting to customize/modifiy should be operating properly in its stock configuration. Sincerely, Macster.

See info on the hack http://www.ppbb.com/phorum/read.php?6,1509504,1509681 This is why I don't think the ballast resistors are not fried. To determine that the problem is the resistor and not some other part of the system, get in the car, start the engine, and put your finger on the appropriate low-speed fan resistor (see below for diagram). Press the A/C (snowflake) button on then off. You should be able to feel the relay click. If not the problem is the fuse, the relay, or the wiring. I removed everything and left it bone stock without jumpers switches etc. The low speed fans come on at 218F. Could the climate control hack be reporting the wrong temperature?

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The numbers posted in the link for the fans coming on is wrong based on my info and based on my observing the Obd2 coolant temp while noting when the fans come on and when they go off. But different year cars may have different fan on/off temperature thresholds. As for the finger on the relay trick I've never tried that. When I took the car in for the non-functioning radiator fan the tech very quickly id'd the resistor as the problem but I didn't ask him how. The PST2 offers him the ability to control the fans independently of each other and the temperature sensor. He showed me the old resistor and it looked quite sick to me. I have been told before this and the tech also confirmed it, that the passenger side resistor is very prone to being splashed from water that collects along curbs and such and I've hit my share of water with the Boxster. (The Turbo resistors are quite well protected, just in case you wanted to know. I do not know how well protected/shielded the 996 resistors are.) Anyhow, if the relay is clicking when you turn on the A/C compressor then the climate control hack may be at fault. I do not know anything about the hack but the last thing touched is always the first thing suspected when a symptom at least related to the hack appears. And I think the symptom you report is related enough. Sincerely, Macster.

If the low fans were turning on.... And later on When the temp rises, the hi fan kicks in. There is nothing wrong with you resistors. I guess I missed the point of your question. I did the hack, but only to turn on the hi fan manually and it works great. Did you Do the engine fan as well.

Yes I did the engine fan as well. The other hack bypasses the low speed and kicks the fans into high speed. My question is why does my car not have the fans come on until 218F(according to the climate control display) - the fans kicks in then. I hacked it so now the high speed kicks on not the low speed. Macster wrote that the fans should turn on at 212F - what causes them to come on?

you will see some inconsistency with the display....it is not that accuarate. I would try to gather more data on where the on off is taking place. If there is a range of the on/off is taking place.... hopefully the range is not that wide and you will know what is normal with you car.