(348) A/C evaporator fan motor relay

Wade, the original relay switches two terminals either on or off, whereas the new relay switches between two terminals. Might not make a difference if your use case only switches a single terminal, but that terminal would have to be in the correct location in the socket in order for it to work. Personally, I'd just trade it for another relay with the correct layout.

HTH,

///Mike

 

Wade, you can keep the new "wrong" relay, 348 has about 5 relays of this type of which three are for the headlamps including the headlamp motors. The relay you are looking for is a very standard relay, also called "universal 5-pin relay". It is surprising that the shop gave you a "special" one.

 

Cool (so to speak).

Where is that relay located? My condensor fan isn't running, so I guess I need to have a look.

 

Thanks, Wade. I figured it was one of those relays but wasn't certain. It seems like the system is low on refrigerant, so that's probably why the fan isn't working. I figured it would come on with the compressor, but it's apparently on a pressure or temperature switch. The compressor clutch engages, but the condenser fan does not run and there's no discernible change in the air register temperature.

Waiting on my maxi fuse holder to arrive to replace the toasted OE holder. This place is great-- no telling how long it would have taken to find that fuse if I hadn't seen that thread. As it was, it's the first place I looked when trying to figure why the A/C isn't cooling.

Thanks again for your reply.

 

I believe the pressure switch that comes into play if refrigerant is too low cuts power to the compressor as well as the condenser fan, so if you hear the click of the compressor clutch engaging when the A/C is turned on, then you at least have enough pressure in the system that the pressure switch isn't a factor. You can confirm that by using a short piece of wire or a paper clip to connect the 2 wires going into the plug on the pressure switch (the 2 wires going into the device sitting on top of the dryer). Of course having enough pressure to keep the switch open doesn't mean that there's enough refrigerant to cool the car down

 

There are two pressure switches, one is a Low pressure (disable the whole AC system), the other is High pressure. The High pressure switch operates the condenser fan. It is designed in this way so that, when you are moving, the air flow will naturally cool the condenser and this will maintain the pressure below the fan switching point. When you stop or drive slowly, the natural air flow will not be much and this will cause heating-up of the condenser and the pressure will go up. Higher pressure, via the High pressure switch, will switch the condenser fan on. The intention of this design is to "save electricity" i.e. the condenser fan will not run when not necessary.

Bypassing the High pressure switch will cause the condenser fan to run every time the compressor runs. I have a modified AC system using a mechanical thermostat which cycles the compressor on-off and my condenser fan runs together with it (I bypassed the High pressure switch). I do not know whether the original AC system also cycles the compressor on-off or whether the compressor, like on some other cars, runs all the time and the temperature is controlled by the air flaps. If this is the case, then bypassing the High pressure switch will cause the condenser fan to also run all the time (not good). If the compressor cycles on-off, then the bypassing is ok. You will actually get a bit better cooling if the condenser fan runs every time the compressor comes on.

 

Thank you, Paul, and m.stojanovic, for the additional details. I know I should have looked at the wiring diagram but the car needs other things as well, so I was putting that off until the new fuse holder arrives. Sounds like there's no reason to assume that the condenser fan won't run, but that it should be tested prior to putting the car in service. Can you tell me where the high pressure switch is located? Seems like there's one switch on the drier, which I'd assumed was the low pressure switch, but maybe not.

Thanks again!

 

The switch near or on the receiver-dryer is the high pressure switch (this is the high side of the compressor) which operates the condenser fan. I am not sure where the low pressure switch is (there may not be one).

What I didn't like about the concept is that the system has to actually start overheating (which causes the refrigerant pressure to rise) before the condenser fan comes on. This is perhaps acceptable in moderate climates but not in tropical (Malaysia in my case). Before I bypassed the high pressure switch, it took fairly long for the fan to come on, I could feel the cooling coming down before that and I noticed that the high pressure piping (before and after the receiver) was getting pretty hot prior to the fan switch-on.

 

Thanks, once again.

As an aside, the condenser fans in my X1/9s are actuated by a temperature switch clamped to the high side line. It probably comes on a little later than it should (my climate is not as bad a Malaysia's, but it does get really hot and humid here) but it seems to work pretty well in terms of determining when the fans should run and when they shouldn't.

I guess the ultimate arrangement would be if the condenser fan ran any time the compressor clutch was engaged and the speed of the car was below, say, 30 mph. I'm *very* partial to great A/C, so that might be a project for the future. Shouldn't be too difficult to use the speedo signal as a control input, and to make the speed where the fan comes on variable, so we could choose the best time for it to shut off through trial & error.

Thanks again for the help!