A/C button only activates aux fan intermittently.

[Wishno87]

Been assembling my A/C install in my m50 swapped car and I'm having problems with my aux fan. I replaced the fan with an aftermarket electric fan but the system is otherwise stock.
The fan will work on high/low if I heat up the temp switch with a heat gun but the manual override via the snowflake button only works intermittently. Will not work when the motor is cold and usually will not work untill the motor warms up. Once it's on though I hear a clicking of relays under dash on the drivers side in 10 second intervals. What's going on?

[MyE30]

if the fan works as advertised with the temp switch then your problem is between the A/C switch and the Normal Speed Relay. Make sure your switch is good. If it is, then make sure the Normal Speed Relay is good. If it is good too, then verify your diode, ground and power wires in that circuit.

[Wishno87]

Thanks for the reply!
The normal speed relay is the one in the fuse box right? I thought the AC switch turned on the high speed one? And where is this diode and what is its function in this application?

[MyE30]

the a/c switch controls the normal speed relay. the relay is located in the main fuse box in the engine bay. the diode is located under the relay. it connects to the 86 pin of the normal speed relay. you can bypass the diode to verify if it's bad.

[MyE30]

the diode is an electrical check valve that only allows current to travel in one direction. the purpose of this particular diode is to stop power from flowing to the a/c compressor controls when the fan is activated by the temp switch.

[e30rapidic]

I just went through something similar to this. I ended up bypassing the AC compressor switch that plugs into the back of the slider assembly.

You can bypass the diode in the fusebox of the engine is cold. I did without issue.

[Wishno87]

So I worked on this for a while yesterday.
Changed out the diode with no change. Changed out the a/c button with no change. Last I went looking around under the dash to see what relay I was hearing clicking. The clicking was from a "a/c relay" and I unplugged it but the fan still works. I have not confirmed yet if it still works when the motor is cold.
I checked out my friends 86 and he did not have this relay. Anyone know anything about this relay?

[FLG]

Can't add much but I've got the same relay click. I no ac in my car and use the fan for cooling. Relay clicks when it's on... Never had an issue tho

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[MyE30]

So I worked on this for a while yesterday.
Changed out the diode with no change. Changed out the a/c button with no change. Last I went looking around under the dash to see what relay I was hearing clicking. The clicking was from a "a/c relay" and I unplugged it but the fan still works. I have not confirmed yet if it still works when the motor is cold.
I checked out my friends 86 and he did not have this relay. Anyone know anything about this relay?

keep in mind that your fan is controlled by two relays; the "normal speed" relay and "high speed" replay. The normal speed relay is activated by the snowflake button on your dash and the high speed relay is activated by the temp switch on your radiator. i believe you already know this.

what is the year and model of your car?

[e30rapidic]

Try what I did and remove the electrical plug that goes to the back of the slider assembly and jump the connector. See if that works. Sometimes the contacts on the sliders get dirty or worn.