A different way of hooking up an e-fan?

[Fett]

The back story goes like this, I installed a Taurus e-fan using a VW thermo-switch. Works perfectly, but my problem is I hooked it up to the high speed wire, which was completely unnecessary. I tried, but never hooked the fan up to my AC, as I never really use AC and was thinking of deleting it anyway. The fan setup works great, but when it kicks on it is a HARD jolt to the system, because I wired it to the high side. The fan comes on when it is supposed to and turns off when it is supposed to, but it only comes on for a few seconds, and the cycle is short. So during a drive the fan comes on and kicks off in very short cycles. I also notice that obviously the AC blows much colder when the fan is blowing. So I want to wire the fan up the way it would normally work, with the low speed coming on with engine temp and the high speed only coming on when the AC is on.

With a CCRM setup, the CCRM basically shuts off power to the low speed wire when the AC is on. I am thinking of finding a way to wire the low side through my current system of the VW switch and relays, then have the high speed hooked up to my AC coil (or cycling switch) so the high speed only comes on with the AC and the low speed is what switches on with the thermo-switch. But I don't think I can simply wire it that way.

I am afraid that if I am driving around with the AC on, the high speed will be on....then when the engine temp triggers the thermo-switch the relays will send power to the low speed side of the fan. In other words, with the AC on there will be times when power is going to both the low and the high speed wires on the fan.

Do electric fans have their own saftey feature built in that would allow me to do this, or do I need to find another way of wiring it in? Again basically I want to leave my setup how it is, just move the power wire from my relay to the low speed, then wire in a relay from the AC coil to the high speed wire.

 

[Mustang5L5]

I forget how the A/C clutch works, but the wire harness going to the clutch is either a 12V hot wire or is a switched ground. If you determine which it is, you can tie this wire into either the hot side or grounding side of the switching leg of a relay and use that to activate the high speed side.

Powering the low and high speed side simultaneously should not have any negative effects

Another way you can run it is to use two temp sensors. Run a low temp sensor to the low speed side and then a slightly higher temp sensor for the high speed.

That way the fan will normally operate on the low speed and the high speed will only kick in if the temp starts to creep up higher.

Then you can wire in the A/C clutch to the high speed relay as well and get dual activation (when A/C is on and if temp shoots way up)

 

[HISSIN50]

Chris, smply switch the VW switch set-up to the low side as you propose. Then use the HVAC feed (From the HVAC panel to the inlet of the LPCS) as your trigger for when the AC is on. This way, the fan stays on the entire time the AC is on, rather than cycling with the AC clutch.

Dont let high and low speed engage simultaneously. You can use a relay to interrupt the low side trigger when high is engaged (to keep both speeds from running at the same time).

With your CCRM analogy, if it was pertaining to SN95 CCRM's (I'm fairly well versed in them), it's actually the SN95 PCM which does the switching and fan overlapping (for fan speed switching from low to high). The CCRM itself is primarily a box of 5 relays. There's also an EDF relay control box. It would be easier to simply use the SPDT interrupt relay idea.

Good luck bud.

 

[Mustang5L5]

Ah dammit i didn't think about the clutch cycling.