What the hell is this?!

[c0rbin9]

UPDATE: Dual temp switch is toast?

I replaced my A/C receiver drier and found that the pressure switch was just dangling from the old drier with the compressor side of the plug jumpered.

I'm thinking I'll need a new pressure switch. My question is what is this other plug? It is a 3 prong plug but 2 are jumpered as you can see in the pic. Also my aux fan doesn't work and I'm trying to troubleshoot it. Car is a 91 318is.

Http://imgur.com/SJfg35x

[jeffnhiscars]

95% of the time, a non working fan is the resistor. Check for 12v at the lower terminal and if younhave juice just jump it and be done with it.

[AndrewBird]

90% sure that is a factory plug with the jumper. Not exactly sure what it is for/why it is like that, but I think it is stock.

[c0rbin9]

I agree that it looks factory - I think it's for the aux fan. Still, my pressure switch was jumpered (with a yellow wire) by the previous owner.

Ideally, I'd like my aux fan to work as stock. It's pretty hot here in Houston this time of year and I need the extra airflow when temps climb.

I was looking at the aux fan wiring diagram and I thought I could test the fan by jumpering the 30 amp side of the high speed relay, since it appears to go directly to the fan. Is this correct? I don't see this 3 prong plug on the wiring diagram.

FWIW, when I first got the car, the fan was wired to turn on high speed when the ignition was "ON". Now it no longer does that and I don't know which wiring to check.

[c0rbin9]

Bump. Tried jumpering every combination of the 3 pins on the female side of the plug. Tried jumpering the 30a side of the high speed relay. Neither worked.

Is my fan dead? Which wire should I check for continuity?

[nrubenstein]

Old receiver dryers took two sensors. The new receiver dryers take only one. The factory solution is to jumper the extra connector.

[c0rbin9]

So the pictured connector is for a pressure switch, not the aux fan? So where is the "lower terminal" for the aux fan that jeffn mentioned? My car is a 91' - I thought it would have come factory with the combination switch, which is why I assumed this mystery connector is for the fan.

Really need my aux fan working, my car already has a failing fan clutch and it is not liking stop and go traffic in Texas summer. Trying NOT to blow up the M42. Any help is appreciated.

Update: Did some reading and I see that I should be looking at the temp sensor on the side of the radiator. Can I just unplug the sensor and jump the terminal to power the aux fan temporarily, for a couple days?

[c0rbin9]

Everybody calm down, I figured it out. The aux fan works on both speeds when jumpered at whatever that thing is that plugs into the radiator (dual temp switch?). I didn't want to jumper it for any length of time there because it seems dangerous/fire hazard.

Still no aux fan - tomorrow is gonna be another rather stressful ride to work!

[c0rbin9]

Recap: fan works on both speeds when jumpered at the dual temp switch. I can hear the relays clicking and the fan turns on. Does this mean my dual temp switch is toast?

[Das Delfin]

I think you're chasing this the wrong way

early model A/C receiver driers had two pressure switches: high and low. Late models (and r134a conversions) have one pressure switch that does both. The idea being if the refigerant pressure inside the A/C system becomes too low or too high, the system will shut off the compressor. They have absolutely nothing to do with your aux fan.

Now, there is a 6 pin relay under the dash that controls a bunch of stuff for the A/C, the aux fan being one of them. That could be fried. You know if it's working when the aux fan comes on with the snowflake button. If the fan does come on, it should come on at its low setting.

There is a temp switch (or two depending on the year but I'm pretty sure it's just eta models) on the radiator which controls the high and low speeds on your fan. The idea with this being if your rad gets too hot (you're idling in traffic) it'll come on. This switch has a high and a low setting. When the rad gets to a certain temp it sends a signal to the fan through a resistor (which lowers the voltage and therefore runs the fan at a lower speed). This is your low speed setting. When the rad climbs even higher, the switch will trip the high speed setting, which goes straight through to the fan. Both of these circuits have their own independent relays.

So if you are troubleshooting, first test to see if the fan comes on at all by checking both the low and high speed relays and then jumping the temp switch on the side of the rad. If the relays are good and the fan and its resistor are good, it should come on high and low when you jump it directly. If the resistor is bad, only the high speed will work.

If the 6 pin A/C relay is bad, your fan will still work when directly jumped like I was saying above but won't come on with the A/C. If it's good, the fan should still come on even if your A/C pressure switches are bad.

Just to recap.. the pressure switches on your A/C receiver drier have nothing to do with your aux fan. They control the signal to the compressor only

The thing you're probably looking for is called the evaporator temperature regulator and is located under the dash on the drivers side, tucked up with the evaporator etc. You can get to it by removing the panel under steering wheel and looking up

[c0rbin9]

I think I figured out the aux fan problem, now I'm just trying to figure out what the hell the connector is that I provided a picture of in my OP. More for curiosity's sake than anything else.

I'm kind of hitting on a lot of separate issues with my car in this single thread.