I see that lots of folks like to add a cooling fan manual override in addition to the automatic thermoswitch control. Thinking of doing the same on my Mk4. As things stand now, I'm not using any of the fan control circuitry in the RF wiring harness, as my EFI processor takes care of things along with its own dedicated thermoswitch. Probably a simple matter to utilize the RF wiring to add a parallel circuit, but it's not immediately obvious (to me, anyway) how to go about doing this. Anyone have a simplified diagram or schematic showing how you've accomplished this?
You need to review your efi system schematic and see how it controls your fan. In my e-street efi the control module supplies a path to ground when it calls for the fan. in my case I took the RF fan thermo switch wire to the module and also a parallel circuit to a switch on the dash and then to ground.
Thanks. I probably didn't make myself clear enough in that I'd prefer not to disturb the EFI circuitry but would rather add a separate circuit to enable manual fan control. Simple enough except that if the two circuits that provide power to the fan come together at the positive lead on the fan itself, there is the potential for the manual circuit to backdrive the EFI circuit if the EFI circuit happens to be off. I suppose a diode on the EFI side will prevent this, but was hoping for confirmation that this will work from someone who's also added a separate, dedicated manual control circuit.
The RF harness uses a relay to control the fan. The circuit I'm describing is on the control side of the circuit. You are only dealing with the coil on the relay and not the fan circuit. My efi module provides a ground for the relay. We're only talking about milliamps. My dash switch offers a separate path to ground for bypass. There is no chance of back feed issues from the fan. I can't think of a single reason to create a completely separate control circuit.
Originally Posted by karlos
Thanks. I probably didn't make myself clear enough in that I'd prefer not to disturb the EFI circuitry but would rather add a separate circuit to enable manual fan control. Simple enough except that if the two circuits that provide power to the fan come together at the positive lead on the fan itself, there is the potential for the manual circuit to backdrive the EFI circuit if the EFI circuit happens to be off. I suppose a diode on the EFI side will prevent this, but was hoping for confirmation that this will work from someone who's also added a separate, dedicated manual control circuit.
Not sure that the diode is really necessary when wired in this manner. Some say that without it the ECU can detect the newly added ground path, which will result in a fault code.
Yes. But you need to verify how your ECU works with regards to the fan switch. My ECU provides a ground for the fan switch so it works just like your diagram. No diode needed for my application. Works perfectly.
Originally Posted by karlos
Like this (modifications shown in red)?
Not sure that the diode is really necessary when wired in this manner. Some say that without it the ECU can detect the newly added ground path, which will result in a fault code.
Karlos, what manufacturer of EFI are you using? Never did say...
It's a Pro-M EFI system. I need to check with Chris Richards to see if the Pro-M processor provides a ground path (as diagrammed above) or a +12V signal to the fan. I'm not sure which it is at this point.
Don't bother. A lot of trouble for no gain. With a programmable ECU you just set the cooling fan where you want it, and forget it. I installed a switch like that, but never used it. Eventually, I disconnected that circuit and used the switch for something else. Don't make things harder than they need to be.
"Electric cooling fan control built right in! The wiring is already in the harness, and the parameters are already in the processor, all set up and ready to go. The Pro-M EFI processor will automatically turn the fans on and off based on coolant temperature, and will turn them on when the air conditioning compressor runs. NEW FEATURE! We’ve now added a “Soft Start” feature to the cooling fan controls!"
The "Soft Start" feature makes me think that you can direct wire the fan to the controller without the use of the Relay as you mentioned in your original post. If you use the "Soft Start" feature I do not know how you would be able to provide a bypass switch. The Pro-M site states that your system is fully programmable so perhaps there is a way to provide an input from a switch programmed to over ride the fan controls. These look to all be questions for your Pro-M representative. Hope it works out. It looks like a good system.
Don't bother. A lot of trouble for no gain. With a programmable ECU you just set the cooling fan where you want it, and forget it. I installed a switch like that, but never used it. Eventually, I disconnected that circuit and used the switch for something else.
Yes, Iv'e wondered what the likelihood is that I'll actually use it. So whether or not I actually follow through depends on how easy it is to install. Will probably go ahead if it's as simple as adding a simple switched ground path.
Originally Posted by Bob Cowan
Don't make things harder than they need to be.
What? And not take advantage of one of my strengths??
Hey Karlos, I'm also using the Pro-M system but I opted not to do the manual overide route. My EFI computer was before the new "Soft Start" feature. Assuming it's a software update...I should have it with the newer download. Going to attempt my first start this Saturday. You are making me think now, I used the Pro-M dedicated blue (larger gauge than RF) fan wire to the fans + power and for the fan's ground wire, grounded it to the frame (I will double check when I get home). Talked a lot with Chris from Pro-M and just got done with all the programming for the ECU and O2 gauges & sensors. If you need any advice (probably from my mistakes) PM me...
Chris
Last edited by cgundermann; 07-19-2016 at 12:50 PM.
Thanks Chris - will keep you mind. Best of luck on your first start. I put battery power to my car for the first time last weekend, so I'm not too far behind you. Everything appears to work as intended. Got the wideband controllers calibrated, verified the fuel pump works, spun the engine over with the starter, would probably run if it had fluids in it.
Real happy with how clean the EFI harness install ended up. Made a couple brackets to support it at the back of the engine and adjusted the length of a few of the breakouts. Will look pretty much like an old school carbed engine with the air cleaner in place.
Thanks! Think we are pretty much at the same stage - have all fluids except gas and have tested all electrical and turned her over. The cable conduit brackets is a good idea. I have mine strategically hanging taught and also made some adjustments. If need be, I might fab some support brackets. Different EFI intake setup (old school 5.0) -
Not sure where you mounted your Innovative Motorsports Wideband O2 gauges, but Summit has a two gauge pod that hold them and I inverted it and mounted it under the dash. They even had a carbon fiber one that is roughly close to my carbon fiber dash. Only reason I am waiting to fire her up, is my wife wants me to wait till Saturday for my 53rd birthday. It's good...because I am triple checking everything and learning the Pro-M diagnostic software.
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Originally Posted by karlos
