Electric Fan Wiring

[SPF Required]

Hello! In an effort to fix a hot start issue I have been having with my EFI, I am contemplating the installation of an electric fan. The EFI unit (FiTech) does have fan control, but I am unsure of some of the other wiring for the relay and where to pull the positive side from.

I have a 1968 Chrysler 300 with a 440. I have a relay, and the fan. Just not quite sure of the wiring layout. while I continue to research some things on this end, I figured I’d ask all my C Body Buddies for some advice too. I have to assume someone on here has wired one of these into their car....? If so, any chance you could share a diagram or some pics??

thanks!

 

[mopar440]

Does the efi provide ground or power for triggering? That would affect how you wire it

I just ran both positive wires ( through a 30 amp fuse) straight to the battery. My switch inside just grounds the relay, turning the fan on.

 

[SPF Required]

Does the efi provide ground or power for triggering? That

Good question.... this is what it says in the FiTech manual: “Fan Circuit #1. This wire goes to the ground terminal of the fan relay.”. I am not an electrician, but my gut is telling me it is providing the ground... right?

 

[Big_John]

Good question.... this is what it says in the FiTech manual: “Fan Circuit #1. This wire goes to the ground terminal of the fan relay.”. I am not an electrician, but my gut is telling me it is providing the ground... right?

What I would do is use a Tyco/Bosch relay and wire my source from battery connection on the starter relay.

Post #30 and #85 would be connected to the battery connector.
#86 would go to your "Fan Circuit #1"
#87 would connect to the positive connection on the electric fan and you would ground the negative connection to the body.
#87A is not used.

 

[SPF Required]

As always @Big_John Thank you for the details. Just making sure I am tracking this correctly....

the ‘source’ are wires from #30 and #85 and go to the stud on the battery relay (I will likely use red wires). I recently did the Ammeter and underhood bypass and that stud is starting to get crowded. Will this be an issue adding a couple more wires? I assume since 30 and 85 are going to the same location, I can wire them together in one connection? Also, would this need a fusible link?? Also... any suggestion on gauge of wire? (sorry for all the add on questions)

#86 - check
#87 - check
Ground from fan - check

thank you!

 

[Big_John]

As always @Big_John Thank you for the details. Just making sure I am tracking this correctly....

the ‘source’ are wires from #30 and #85 and go to the stud on the battery relay (I will likely use red wires). I recently did the Ammeter and underhood bypass and that stud is starting to get crowded. Will this be an issue adding a couple more wires? I assume since 30 and 85 are going to the same location, I can wire them together in one connection? Also, would this need a fusible link?? Also... any suggestion on gauge of wire? (sorry for all the add on questions)

#86 - check
#87 - check
Ground from fan - check

thank you!

What I would do is one #12 (or larger) to #30 and then just jumper over to #85 with a smaller wire. Maybe #16 or #18. When in doubt, always err on the large side. Then you will only have one wire at the relay.

#12 to the fan.

I'd do an inline fuse from the starter relay. That would cover everything. The fusible link is great for the entire car as it won't blow if it gets overstressed, but the fan really needs to just shutdown if there's a short. See what the fan manufacturer recommends for fuse size and wire size too.

If the relay is getting too many connections, you can always add a power post like this. Search for "power post" on eBay.

 

[Davea Lux]

If you have access to a thermal temp gun, take the temp of the ecu when the car does not start. If it is overheating, you might want to change the location of the unit. We moved a couple of the electronic packages to the front of the core support with no need for a cooling fan. Will take some extra wire but it seemed to work well that way.

Dave

 

[SPF Required]

Thanks for the advice Dave. Unfortunately the ecu on a FiTech EFI is integral to the throttle body unit. I have been working with them via email and I think we have come to the conclusion that it is experiencing a ‘heat soak’ issue. The hot start issue really only happens on warm days (~+90 degrees). And it only when I make a short stop after cruising for a while.

I have wanted a fan for a while so this is just the issue to finally get me motivated. And I’ll learn a new skill along the way. I have never dealt with relays before (as if one couldn’t tell).

 

[Davea Lux]

Thanks for the advice Dave. Unfortunately the ecu on a FiTech EFI is integral to the throttle body unit. I have been working with them via email and I think we have come to the conclusion that it is experiencing a ‘heat soak’ issue. The hot start issue really only happens on warm days (~+90 degrees). And it only when I make a short stop after cruising for a while.

I have wanted a fan for a while so this is just the issue to finally get me motivated. And I’ll learn a new skill along the way. I have never dealt with relays before (as if one couldn’t tell).

Check the heat riser to be sure it is not stuck shut as that will be a potential source of excessive heat to the throttle body. Most EFI conversions suggest the blocking of the heat riser port in the intake for that reason.

Dave

 

[SPF Required]

So now I am really showing how much of a novice I am. Where would I find the heat riser? What’s it look like?

Edit: I looked it up on line... I see it’s the valve on the passenger side exhaust manifold. We actually pulled that out when we installed the EFI.

 

[Davea Lux]

So now I am really showing how much of a novice I am. Where would I find the heat riser? What’s it look like?

Usually on the passenger side exhaust manifold there will be a flapper valve where the manifold meets the exhaust pipe. It should move freely. The valve has a thermal spring that closes the valve on a drop in temperature when the engine is cold. As the engine warms up, the spring weakens and that valve opens. If the valve is stuck shut, exhaust is diverted thru the heat riser passage under the carb or in this case EFI. This will cook the EFI unit electronics for this type of EFI or cause it to shut down. Check you instructions, most of the time a heat riser is not needed with EFI.

There is an after market intake gasket that blocks the heat riser ports as the heat riser passage is not needed with EFI. If you installed the EFI yourself, that is probably the source of the excessive heat if the heat riser passage is not blocked. You will also need to block the heat riser in the open position by tying it down or better yet just remove it. What year vehicle is this and which engine?

Dave

 

[SPF Required]

Ah yes.... that thing. It is gone. Removed when the EFI was installed.

thanks Dave

 

[SPF Required]

I am chalking up today’s work as a success on this fan project, but have run into an issue that will still need some diagnosing (and probably a bigger fan). Here’s some pics of the project:

wiring up the relay to the fuse:

wired relay based on the description above:

fan secured to the radiator:

installed relay to the starter relay (all those wires get concealed behind the washer bottle):

the issue I am having is the fan comes on as soon as the engine is fired up. Not when key is on, but when the engine is running... even when cold. Again, not a fail because the fan is only running when the engine is on.

I set the fan on temp at 190 and the fan off temp at 175. I let it idle for awhile, got up to 200 with the fan still running. My thought here was if it got to 190 and the fan turned off, they perhaps it was just a crossed wire at the relay...

Turned the engine off and the fan stopped. Still a success since it won’t drain my battery, but clearly not operating as intended to be switched on and off by the EFI.

Did some research and found the FiTech install instructions online. They include the following diagram for the relay wiring (sorry I didn’t know about this early):

This is the first time I have ever worked with relays, but I am a quick study. I think I could easily rearrange the connections on my current relay to match the image above, I am just in the dark on what the ignition/accessory circuit fuse line is going to #86. Could I get away with using that jumper to go to 86 instead of 85? And move the fan circuit from 86 to 85??

I appreciate all your input!

 

[Davea Lux]

#86 is the power control circuit for the relay, it needs to be hooked to the ignition switch so that the fan will shut off when the key is off. Look at your fuse block, most have a lug terminal for a plug that is labeled "accessory" from the ignition switch. Check the lug with a test light, if the test light glows when the key is turned on, you have the right one. Once that is determined, run a lead to #86 from the lug. That lead should have an in line fuse to protect the circuit.

Dave

 

[Big_John]

I am chalking up today’s work as a success on this fan project, but have run into an issue that will still need some diagnosing (and probably a bigger fan). Here’s some pics of the project:

wiring up the relay to the fuse:
View attachment 397161

wired relay based on the description above:
View attachment 397163

fan secured to the radiator:
View attachment 397162

installed relay to the starter relay (all those wires get concealed behind the washer bottle):
View attachment 397164

the issue I am having is the fan comes on as soon as the engine is fired up. Not when key is on, but when the engine is running... even when cold. Again, not a fail because the fan is only running when the engine is on.

I set the fan on temp at 190 and the fan off temp at 175. I let it idle for awhile, got up to 200 with the fan still running. My thought here was if it got to 190 and the fan turned off, they perhaps it was just a crossed wire at the relay...

Turned the engine off and the fan stopped. Still a success since it won’t drain my battery, but clearly not operating as intended to be switched on and off by the EFI.

Did some research and found the FiTech install instructions online. They include the following diagram for the relay wiring (sorry I didn’t know about this early):
View attachment 397165

This is the first time I have ever worked with relays, but I am a quick study. I think I could easily rearrange the connections on my current relay to match the image above, I am just in the dark on what the ignition/accessory circuit fuse line is going to #86. Could I get away with using that jumper to go to 86 instead of 85? And move the fan circuit from 86 to 85??

I appreciate all your input!

Changing to the diagram shown isn't going to solve your issue.

It looks to me like the FI controller only lets the fan run while the engine is on anyway, so hooking the + wire to the accessory circuit just means there's no + power except when the key is on... But that makes no difference if the - side is controlled by the FI... Which appears that it doesn't power it up until you have the key on.

85 and 86 are interchangeable. One has to be + and the other has to be -. Doesn't matter which one is which. It won't change anything.

It sounds to me that the thermostat isn't really working correctly.

If this were mine, I'd want it to run (controlled by the thermostat) all the time like a modern car does. That would help combat your hot soak problem.

 

[SPF Required]

Thank you for the additional advice. And based on what I can tell, the EFI won’t run the fan until the engine is actually running. Key on, but engine not running = no fan. I am researching the settings for the FiTech to see if it is a software issue (ie pilot error).

if nothing else, I am enjoying learning a new skill.

 

[SPF Required]

Swapped out the 12” fan for a 16” one earlier today. I Will be spending more time this weekend diagnosing why the fan stays on when the engine is running, but that’s got to be better than not running at all. I may swap out the relay and see if that helps.

while I was looking around online, I found this diagram that does a great job of putting into pictures what @Big_John described above. I am a picture guy so I figured this might help others who are learning about relays.

I’ll report back in a couple of days!

 

[SPF Required]

So I cannot explain it, but everything worked as desired today (I didn’t do anything but install a bigger fan). I didn’t touch the wiring relay or adjust the settings on the FiTech. Fan on at 190, fan off at 175. The only adjustment I made after the fact was to swap the + and - connections at the fan to get it to spin clockwise (pusher mode).

Temp was up to 213 with engine off and when parked for a few minutes after a 40 min drive. Started it up and was able to watch the temp start dropping while idling.

I’ll clean up the wiring after a couple of more road tests, but so far so good!

thank you all for your help on this project.

 

[SPF Required]

Had a couple good tests so I decided I’d finish up with cleaning up the wires and call it done!

thank you again for your advice and sharing of knowledge.

Wires up in the cable wrap:

Washer bottle back in to conceal all my wires (this fan and my FI harness):