996 Fan Operation Question

[alexandros075]

Hi All, last week I noticed my "new to me" 996.1 C2 3.4 m/t, temperature gauge was slightly higher than I am used too when sitting in traffic (all the cars I had always sit on the middle or just below but this is my first Porsche).

After reading lots of threads about resistors, relays etc. I thought maybe both resistors where faulty. I did quite a comprehensive test and this is what I found out:
[*]40amp Fuses are both ok. Car does not has the original resistors, but has the RS components gold resistors that a lot of people tend to fit when the originals go bad.[*]Relays are all ok, tested all 4 in all 4 different position and I could hear/feel them click. [*]Jumped each relay connection point and I could hear the fans turn on. I am also using the HVAC controller hidden menu to monitor temps rather than using the gauge. [*]Fans will come on after I switch A/C on. When the car is cold >93 deg C the low speed relays click and the fans switch on. When the car is hot <93deg C the high speed relay click and the fans switch on. [*]I thought at this point the fans where switching on only when the A/C was switched on, but I left it idling with the A/C off and when the temperature hit 108deg C the high speed fans switched on and the decklid fan also switched on. (I took some pictures of the temperatures when this happened please see images attached)[/LIST]At this point I am not sure what to think. Fans seem to be operating "normally" I guess, but the temperature gauge does seem a bit high to me. I did a mixture of slow city driving + car stop idling for quite a while to achieve this temperatures. Is this normal and I am being way too paranoid? Or is it worth taking it to a specialist to have a look at it? I thought I asked before I embark on the journey of start to change resistors/fan units.

I read that 3.4 models have a more realistic temperature gauge that moves up and down more noticeable than the 996.2 but again I could be wrong. The car had a new water pump/radiators in 2020. And the AC Conders are also relatively new (installed 2022), so I will probably say there is not a huge debris build up.

Many thanks for your help!

 

[j7agy]

Apologies if I’ve misunderstood, and I’m no mechanic, but you‘ve undertaken a fairly comprehensive electrical test, and assume you have an electrical issue. Perhaps it’s a sticking thermostat - is that possible? Wouldn’t that cause your temp gauge to sit higher?


John

 

[Richard_Hamilton]

There is often a difference between the gauge and the actual temperatiure.

This article might be of use:
https://www.porscheclubgb.com/forum/tm.aspx?m=330170
You may not be able to access it as a guest, so I have copy and pasted it here:

[h1]Cooling Fans & Coolant Warning light[/h1]There have been a few queries on the main 996 forum on these subjects, so I thought it might be a good idea to put a more permanent record on here. These were taken from the workshop manual (courtesy of Porsche AG):

COOLING FANS:
Switch-on conditions for coolant or condenser blower motors: Stage 1 is switched on when the coolant temperature is >100°Corthere is an A/C demand, the intake air temperature is >8°C and terminal 15 (ignition) is switched on. Stage 2 is switched on when the coolant temperature is >105°Corthe refrigerant pressure is >16 bar. Switch-on conditions for engine compartment fan: The engine compartment fan is switched on when the engine compartment temperature is >80°Corthe coolant temperature is >102°C. After-running of engine compartment fan If the ignition is switched off and the engine compartment temperature is more than 60°C, the DME control module remains in readiness for another 20 minutes. During this time, the engine compartment temperature is retrieved every 10 seconds. If the engine compartment temperature is >85°C, the engine compartment fan is switched on for 20 seconds. If the engine compartment temperature is still >85°C after this time, the fan remains on for a further 30 seconds. COOLANT WARNING LIGHT(in the temperature gauge) Four functions of the coolant warning light:
1. Engine coolant level too low
- light flashes slowly (0.5 Hz)
2. Engine compartment temperature too high
- light flashes slowly (0.5 Hz) (engine compartment blower might be faulty)
3. Engine coolant temperature too high
- light is lit; pointer on the right
4. Temperature sensor at water outlet faulty
- light flashes rapidly (1 Hz); pointer on the right

Note
The temperature warning in point three is indicated if the conditions "engine coolant temperature too high" and "engine coolant level too low" are present simultaneously (1Hz = 1 flash per second. 0.5Hz = 2 seconds per flash)

 

[alexandros075]

Apologies if I’ve misunderstood, and I’m no mechanic, but you‘ve undertaken a fairly comprehensive electrical test, and assume you have an electrical issue. Perhaps it’s a sticking thermostat - is that possible? Wouldn’t that cause your temp gauge to sit higher?


John

Thanks John, yes it could be a sticking thermostat. Its on my list to do a lower temp thermostat so I will probably take it to precission porsche for a service and ask them to change it anyways. I belive the fault is still electric as based on Richard's post the fans are not operating as they should, if the car is running hotter due to a sticking thermostat that would mean the fans would operate longer or potentially all the time which they are not. They only seem to kick in at the highest speed when abnormally high temperatures are read.

 

[alexandros075]

There is often a difference between the gauge and the actual temperatiure.

This article might be of use:
https://www.porscheclubgb.com/forum/tm.aspx?m=330170
You may not be able to access it as a guest, so I have copy and pasted it here:

[h1]Cooling Fans & Coolant Warning light[/h1]There have been a few queries on the main 996 forum on these subjects, so I thought it might be a good idea to put a more permanent record on here. These were taken from the workshop manual (courtesy of Porsche AG):
COOLING FANS:
Switch-on conditions for coolant or condenser blower motors: Stage 1 is switched on when the coolant temperature is >100°Corthere is an A/C demand, the intake air temperature is >8°C and terminal 15 (ignition) is switched on. Stage 2 is switched on when the coolant temperature is >105°Corthe refrigerant pressure is >16 bar. Switch-on conditions for engine compartment fan: The engine compartment fan is switched on when the engine compartment temperature is >80°Corthe coolant temperature is >102°C. After-running of engine compartment fan If the ignition is switched off and the engine compartment temperature is more than 60°C, the DME control module remains in readiness for another 20 minutes. During this time, the engine compartment temperature is retrieved every 10 seconds. If the engine compartment temperature is >85°C, the engine compartment fan is switched on for 20 seconds. If the engine compartment temperature is still >85°C after this time, the fan remains on for a further 30 seconds. COOLANT WARNING LIGHT(in the temperature gauge) Four functions of the coolant warning light:
1. Engine coolant level too low
- light flashes slowly (0.5 Hz)
2. Engine compartment temperature too high
- light flashes slowly (0.5 Hz) (engine compartment blower might be faulty)
3. Engine coolant temperature too high
- light is lit; pointer on the right
4. Temperature sensor at water outlet faulty
- light flashes rapidly (1 Hz); pointer on the right

Note
The temperature warning in point three is indicated if the conditions "engine coolant temperature too high" and "engine coolant level too low" are present simultaneously (1Hz = 1 flash per second. 0.5Hz = 2 seconds per flash)

Thanks again for your help Richard! I really appreciate it. Ok so definitely my car is not behaving normally as per the repair manual. I think I might have found the cause of the issue, I had a closer look at the resistors and they have been welded to the fan harness very poorly (see images attached).

I tried to measure their resistance value with a multi-meter but had no luck. Then I checked for continuity from both ends of the resistor and nothing, so I would assume that those exposed connections might have shorted them? I ordered 2x new resistors from RS components and when measuring continuity they are continuous from one end to the other.

I will install this new resistors, using good connectors and protect it using heat-shrink tubing to ensure they are waterproof. Hopefully this fixes the issue. If there is something else I would probably take it to precision Porsche as I don’t have a lot of tools to work on the car unfortunately.

 

[andywill]

HI
Just be aware these resistors get very hot and are the connections are more open to the elements than the originals. Some have made a metal bracket to assist their location. If the original brackets are still in place you could adapt them.
Good luck