Fan Thermo switch location?

[BB767]

Trying to figure out where to place the fan thermo switch on the engine. The EFI and temp gauge senders are taking up the two obvious locations on the intake manifold. Besides being the least desirable location my radiator does not have a bung for the switch. Where are most people putting their fan switches?

[weendoggy]

Take the radiator to a shop and have a fitting installed in the tank near the output.

[Itchief]

I used the efi to set and control the radiator fan relay that way I only had to have two temperature sensors

Rick

[Boydster]

Yeah, your EFI should be able to control the fan, that way another sensor is not needed. What EFI ya usin?

[BB767]

I would love to have the EFI control the fan. I have it wired exactly as the FFR manual says to do it but it is not working. The FAST XFI Street says it has a negative feed fan control. I believe the FFR fan control relay needs a positive feed to the relay to make it work. I am no electrical expert by any means but I suspect this is the problem. Now I am stuck with a cut relay feed jumper wire and an EFI controller that does not seem compatible!

[Itchief]

I think that what they are saying is that the efi will provide the ground for the fan relay the same way the relay sensor would

You should be able to connect the fan relay sensor wire to the efi fan lead

You can test your ffr wiring by grounding out the lead for the fan relay sensor and the fan should run

Rick

[BB767]

"You should be able to connect the fan relay sensor wire to the efi fan lead"

I think that is the way I already have it hooked up but I will double check in the morning and try your suggestion for testing it. Thanks.

[Boydster]

Everything you're getting so far is right... the EFI uses its own temp sensor, so the wire that used to go to the fan relay temp sensor now goes to the EFI. EFI just supplies ground to the relay when it needs the fan to run. Fan relay is already powered off the fusebox (Ron Francis).

[phileas_fogg]

Everything you're getting so far is right... the EFI uses its own temp sensor, so the wire that used to go to the fan relay temp sensor now goes to the EFI. EFI just supplies ground to the relay when it needs the fan to run. Fan relay is already powered off the fusebox (Ron Francis).

Agreed.

Since your EFI computer provides a ground signal, the easiest method for having your EFI computer control the fan relay is to simply connect the EFI fan control to one of the RF dark green Thermo Switch wires. Note that RF provides two: one in the front harness intended to go to a sensor in your radiator and one in the sending units harness intended to go to a sensor in your engine block. Use the one that's most convenient & terminate the other so that it can't inadvertently ground.

Since you've already cut the jumper on the fan relay, you've got a bit of repair work in front of you. Don't worry, it's mostly easy; you just need to replace a couple of 1/4" non-insulated spade connectors. To make it easy on yourself, remove the RF fuse box from the car. Next, remove the fan relay from it's socket. The socket will look like this:

auto-relay-socket-with-5-cables by jhsitton, on Flickr

Note that the spade connectors have a small notch at the bottom of them; you can see one in the picture above just above the "m" in ".com".

Remove the two spade connectors with red wires on the back from the relay by inserting a straight pin, jeweler's screwdriver, or special removal tool into the slot to push down the keeper tab on the spade connector. Give the red wire little wiggle & pull on the back of the connector and the spade connector should just pop out.

Insert a new jumper & the RF red fan power wire into a new spade connector and crimp. Insert the other end of the new jumper into a new spade connector and crimp. Insert the new spade connectors into their corresponding relay socket slots, and insert the relay back into its socket. You're done.

The hardest part is working with that relatively short RF red fan power wire while the bulk of it is secured in the wire loom.


John

[weendoggy]

I would love to have the EFI control the fan. I have it wired exactly as the FFR manual says to do it but it is not working. The FAST XFI Street says it has a negative feed fan control.

As others say, if it is a grounded switched control (which is advisable), do it that way. While you're at it, I'd put a toggle in line as well to allow you to have the fan on constantly if everything else fails.

[BB767]

Everyone. Sorry for the delay, I got locked out of the forum for losing my password. John, your detailed post got me on the right track. I am very dissapointed the FFR manual had me (unnecessarily) cut both the wires for the fan and fuel pump relays and attach the wrong wires from the EFI computer for both of them! As I said before, those wires are positive feed wires, the computer uses ground (negative feed) for control! I was able to perform surgery to wire them both correctly but with a few more splices than necessary due to the faulty directions from FFR. All works as it should and first start was finally successful. Thank you all for your input.

[phileas_fogg]

Glad you're back on track.

With regards to the fuel pump feed, check your EFI documentation - or call the EFI manufacturer - for what it provides. My Holley Terminator provides +12V for the fuel pump, and a ground for the fan.

If your EFI is like mine and provides +12V, the easiest way to get EFI power to your fuel pump is via the RF harness. Simply unplug the Weatherpak connector coming out of the fuel pump relay, put a mating connector on your EFI fuel pump wire, and plug them in. Voila; EFI power to your fuel pump. Then you can use the RF fuel pump feed for something else (like an auxiliary jack, seat heaters, or foot box vent fans).

And while you're checking the fuel pump circuit, make sure your inertia switch is wired correctly. Mine wasn't, but thanks to this thread (http://www.ffcars.com/forums/17-fact...-question.html), I corrected the problem before testing.

Cheers,


John

[rich grsc]

Everyone. Sorry for the delay, I got locked out of the forum for losing my password. John, your detailed post got me on the right track. I am very dissapointed the FFR manual had me (unnecessarily) cut both the wires for the fan and fuel pump relays and attach the wrong wires from the EFI computer for both of them! As I said before, those wires are positive feed wires, the computer uses ground (negative feed) for control! I was able to perform surgery to wire them both correctly but with a few more splices than necessary due to the faulty directions from FFR. All works as it should and first start was finally successful. Thank you all for your input.

NO, you can't blame FFR for that. Its your responsibility to follow the directions of the computer manufacturer on how to wire the system. I have a Fast system, and it's a complete stand alone wiring with regards to computer temperature, fan control and fuel pump relay's. It doesn't tie into the FFR harness.

[BB767]

John, mine is just the opposite of yours, it uses the ground to control the fan and the fuel pump. Once I figured out that the computer was using negative control instead of positive everything made sense and was easy to figure out and rewire. the problem lay in the fact that FFR directions assume a positive control for the relays and the FAST directions did not point out that they used a negative control. Once these facts became clear the problems were east to remedy. Thanks again for your positive input.

Rich, I really do not appreciate your negative input and do not understand why you are so defensive unless maybe you work for FAST. No one at FFR is that offended when I ask questions or point out errors in their manual. FAST seems very annoyed when I ask them questions.

I would have followed the directions for the FAST computer had C-Com seen fit to include some! Unfortunately the guidance provided was so vague and convoluted I could not decipher it. Calls to their help desk were not pleasant either. I guess I am not technically oriented enough for them (or you).

Maybe my FAST system is more advanced than yours as it does tie into the FFR wiring harness to control the fan and the fuel pump. On page 35 and 36 of the FFR Chassis Wiring Harness manual, -rev-T, it specifically explains how to make the computer control the fan relay and on page 13 it spells out the same information for controlling the fuel pump relay. These directions are totally wrong for my FAST EFI harness, so yes, I will place some blame on FFR. A simple notice that some systems may have different requirements for fan and pump control would have been nice before I began cutting into the harness as per their instructions! Regardless, once the correct information was obtained, the result was satisfactory, so I am happy whether you are or not. Good day.

[GSides9]

Every one of us has built totally custom cars. That requires that we be a little patient with each other. From what I read here, Fast has a newer system that is wired differently than their older system. We are all still trying to share the best info we have with each other.

Merry Christmas, Glen