Thread: 300Tdi Air Conditioning Fan will not shut down

Don't know much about the Madman units, but it looks like you still need to buy the sender separate? It looks like it can do a lot more (multiple inputs), but more effort to install than a VDO mechanical gauge.

UPDATE!

In the end I gave up with the electrics as my knowledge of auto electrics is some what limited.

So I took the landy to an auto electrician who went over the vehicle yesterday. Hiscomments were as follows:

- Unable to locate a "short" in the wiring - assume that this was either atemporary short caused by the dunking in muddy water that it received threeweeks ago (I told him I had, had some fun with the truck).

I did however point out that I had fitted a temporary capillary temperature gauge and that thiswas when the short happened. Looking at the area around the thermostat housingit was apparent that the gauge outer sheathing (which in the case of this particularcapillary gauge is metal) had been arcing on the No. 1 glow plug. I think thiswas causing the fuse to blow in the fan circuit. Hence, when I removed all thetemporary gauge and associated capillary ancillaries, the short disappeared.

I think this is a valid explanation. Suffice to say I need to repair the sheathing onthe No. 1 glow plug terminal because it burned through!

- With the fan temperature stat disconnected at the thermostat housing and the engineat full operating temperature and with the AC system on, the fan is STILLtriggered by a pressure switch in the evaporator (I didn't know about thisother switch/sensor). This is because as the system is used and the condensergets hot the pressurein the system changes, this is picked up by the pressure sensor in theevaporator and triggers the cooling fan on the condenser. At least this is whatthe auto electrician explained was happening. The fan then comes on and off asand when the system decides it needs extra cooling, and he ran it long enoughto demonstrate to himself that it was doing what it should be doing.

- Having worked through the entire AC system and followed the diagram, he says that thesystem is doing exactly as it should do via the wiring diagram itself. That isto say the system operates as the diagram dictates it should. Obviously that isonly taken at face value, but he did say if I have any other problems with it,just bring it back in (more $$$ I guess for him).

- In conclusion: Having discussed the above with the auto electrician, I asked whatwas the best way to stop the fan from coming on when the AC was not on. He saidthat as he had already demonstrated that the fan will work even with the yellowtemperature sensor disconnected in the stat housing, but with the AC on, whynot put a simple switch into that circuit so I can control the electric fan.This seems like a good idea for the following reasons:

1) I can turn the fan on and off as and when I like, if its a hot day, have it on toprovide the additional cooling for the engine (this is assuming the AC systemis off). If the AC is on, it is likely that the system will trigger the fan anywayas the pressure builds up.

2) Gives me the option to kill the fan when I decide to drive through a river..Hopefullyleading to less electrical issues.

3) Provide speace of mind that the fan isn't going to be on all of the time and therefore apotential fire hazard due to it may be over-working the crap land rover wiringor burning out the fan motor.

In short, I am going to rig a switch up tonight. Then I will start the truck, run it upto temperature and switch the AC on, the fan will be off because the switch isopen. Then it’s just a case of waiting for the system to build pressure so thatthe evaporator pressure sensor triggers the fan on and off when it needs it. If this is thecase then I am happy that my work around is a success.

With the AC off and the switch closed the fan should and will come on, because it is beingtrigger by the temperature sensor in the stat housing.

Conclusion: I still haven’t figured out why the system thinks it needs the fan on all thetime even with the AC off. But I have verified to my satisfaction that it isn’tgoing to catch fire or burn out. It’s just more of a minor annoyance that I couldn’tget to the bottom of it.

Regards

Rob