View Full Version : Question on fan power
So back when I first wired everything, a million years ago, I believe I set the fan wiring up with a manual dash switch as per Jeff K's instructions posted to someone else with the same question at the time. My question is, is the power to the fan through the manual switch HAAT, or only hot with the key on? Back when I had my first start, it did not appear that the fan was coming on, and the temp continued to climb while at idle. I'd like to check the operation of the manual fan switch, and need to determine if it should operate without the key. I'm also not sure now whether the FAST system's control of the fan will override any of the previous wiring that I did. I want to make certain that I don't have any issues in this circuit because of how important it is. Obviously, wiring is not my strong suit! Just trying to check systems out before I get this thing running again.
Thanks
Rick,
If you used the RF fan wiring, the fan relay is ground triggered via either of the two fan thermo control wires; one in the sending unit bundle and the other in the front harness with the fan motor power and ground. Here is a diagram of how I would have wired a manual fan switch.
https://thefactoryfiveforum.com/attachment.php?attachmentid=124226&d=1584473457
Note that there is no power in the manual switch. The switch is simply connecting a ground to the relay trigger (fan thermo control), the same as what the EFI fan control does. I don't have the RF wire schematic in front of me, but I belive the key needs to be in the on or acc positions for the fan to run.
Dave
D Stand
05-16-2020, 04:17 PM
Per my RT wiring, the fan circuit is direct to the battery and will run with the ground trigger with the ignition in any position.
Dave, Thanks for the schematic. I'm going to have to go back through and trace where the wires to my manual switch are coming/going to.
D Stand, So the fan should operate with the manual switch, even with the key off. Thanks for that info.
Back to the shop to try to figure this out.
CraigS
05-17-2020, 06:23 AM
Personally I would prefer it not powered w/ key off.
Craig, I know what you mean. So many items HAAT just leaves the possibility of forgetting one and running the battery down. I'm also wondering, if the FAST system has a fan operation system in it, would having a thermostatic switch, like the Painless #30111 or #30110, create a problem with two systems trying to control the same item? Is it one or the other, or can they work together without stepping on each others toes? I haven't traced all the wiring to see exactly how I have everything run, but I'm pretty sure that the fan didn't come on when I had it running a couple months ago.
Rick,
The mechanical temperature fan switch shouldn't be used with EFI. Your FAST setup is different than my old XFI Street, but should control the fan. A coolant sensor should have come with the EFI and is separate from the sensor for your gauge.
Dave
Dave, That is kind of what I was thinking when I started getting in to this. The FAST system does have a separate coolant temp sensor. I'm just going to have to check to make sure that, like most of my other electrical systems, I didn't bugger it up! I'm pretty sure that the fan thermo sensor wire is connected to the FAST Fan 1 wire. I'm going to have to figure how, and where I can connect in a light to show that the fan is running, and some place to mount the light. I thought that I had all this covered, but with the fan not running when the engine hits temp, I now have my doubts on what I did.
You can can still run a manual switch with a light like my diagram showed. You just don't want to use the temperature switch that came with the kit (used for carburetor fuel systems) and an EFI control. You can check the fan by taking the green wire in the fan wire bundle at the bottom of the radiator and simply grounding it. If the fan doesn't come on, on to other trouble shooting. Did you modify any of the fan circuit in the fuse block? Have you checked the fuse for the fan circuit?
Dave, OK, I think I'm getting myself confused. The wires going to the fan on my harness are a dark blue "cooling fan" and a black "ground". The dark green on my harness is the "fan thermo switch" wire that is connected to the Fan 1 wire coming from the FAST computer. I just tried putting power to the dark blue cooling fan wire from an auxilliary battery, figuring that the ground is already connected, and the fan did not start. I may not be hooking this up correctly since I'm not sure what it needs to get power to the fan. Just a quick question, is that a DP/ST switch in your diagram? Reason I ask is that I have a SP/ST switch currently in that use. The two brown wires, "fan switch feed" & "gauge feed" wires go to one pole and the orange "cooling fan" wire to the other. The two brown wires were already merged together at the connector, so I didn't have to do anything with that other than plug it in to the switch. As a note, my wiring harness is Revision H from 2011, so some wire colors may have changed.
I didn't modify the fan circuit, and the last check of all the fuses, it was OK, just a day or so ago.
Rick,
The blue & black wires are the fan power and ground at the fan motor. If you connect those wires to your battery directly, the fan should run.
What you have described at your manual switch doesn't line up with what I'd expect, but there is no one right way to add a switch for the fan. My diagram is DP/ST simply to add in the lamp that would light if the fan was manually activated using the switch. If your switch is getting +12v, I'm not sure what it is switching?
Your EFI fan control going to the fan thermo control wire is correct. This green wire should run to the ground pin on the fan relay. The EFI simply closes the ground when it wants the fan to come on, same as if you ground that wire yourself.
rich grsc
05-17-2020, 05:45 PM
I hope you are just not correctly explaining what you're doing. The FAST computer uses the temperature sensor to know the operating temperature of the engine. The computer can be set to turn on and off the coolant fan at the desired temperature. The fan wires from the computer are ONLY to operate a relay, not power the fan. I hope you didn't apply power to those wires. Look at and study the wiring schematics from FAST.
OK, I'm going to try to attach the section of the wiring diagram that I'm referencing above. OK so the forum won't allow the page to upload because it is over 200K so I can't attach it here. Anyhow, it's on the Ash Harness page, page 16 in my RF wiring book. It shows the fan switch at the top of the page. I just wired according to the incomplete, and non-detailed instructions in the book. I'll try connecting the fan directly to 12V power to see if I can get it to operate.
Rich, No I didn't apply any power to the wires from the FAST computer, or the dark green Fan Thermo switch wire. I'm just trying to determine if the fan will come on, and why it didn't when I ran the engine previously.
If the wiring diagram in the RF manual is not how I should be wiring this to have a manual switch, with a light or not, then I need to determine what it is I need to change.
Thanks guys.
Rick,
Be sure to disconnect the fan from the harness before testing it. You want to power the fan, not the harness.
Can you snap a photo of you RF wire diagram for the switch you are describing?
Dave, So here is a photo of that portion of the wiring diagram.
https://live.staticflickr.com/65535/49907029376_d860c003b8_z.jpg (https://flic.kr/p/2j37z6J)P5170135 (https://flic.kr/p/2j37z6J) by Rick Paul (https://www.flickr.com/photos/156322842@N02/), on Flickr
I went back out to the shop, and tried connecting the fan to direct power again. Disconnected from the harness, and plugged the wires from the power source to the fan leads. It's not the fan. It powered up no problem. So now I'm trying to figure why the fan switch, wired as above, does not operate the fan. I have to assume that the FAST computer will operate the fan as intended, but I must have the settings incorrect. When I get the intake manifold gasket replaced, and can try starting the engine again, I'll have to check my settings for that.
Thanks.
Rick,
I found a similar version of your harness diagrams (Rev K). It looks like the fan switch is feeding the power to the fuse block for the fan, but the fan is powered by the dark blue wire. I suspect that the switch needs to be on for the fan to run when the relay is triggered by the fan thermo switch (ground trigger).
To test this, disconnect the EFI fan wire from the green thermo sw wire. Turn the fan switch on and then ground the green wire and the fan should run. Turn the switch off and ground the green wire and the fan should not run. If this is what is happening, you'll need to remember to keep the fan switch on when driving the car. You could also bypass the switch and just connect the wires together and skip the switch.
Dave
Dave, So this is making less and less sense to me as to why they would wire this up in this manner. I'll test this out tomorrow, it's not like I'm going anywhere! Just to make sure I'm clear on what to do, once I disconnect the green thermo switch wire from the FAST harness, I just need to take that wire and run it to a ground point directly?
So if this is what is happening, I won't have the capability to turn on the fan manually? How much confidence should I have in the FAST computer to take care of this all the time? Loosing the switch wouldn't be the end of the world. I could use the hole that it was in and wire in a light to show when the fan turns on, and not have to drill a new hole in the finished dash. But saying I did want a manual switch, or it would be a plus to have a manual switch, by abandoning the orange and two brown wires, that currently go to the switch, that will now be connected together to close that circuit, where would the switch have to go so as to not interfere with the EFI control, but just provide a secondary method for turning on the fan?
Yeah, I know. As I've said before, I shouldn't have cut all those shop classes when we were doing electrical!
Thanks
I'm grounding the dark green wire from the RF harness, not the wire from the FASST harness.
Rick,
Well, just thinking that perhaps the original cars had switches to turn pretty much everything off if you wanted to. The newer harnesses no longer take this approach. You could tie the orange and brown wires together to make the fan circuit always hot like the more recent setups and then wire a manual switch per my diagram to have the functionality you are looking for. Let's verify my theory first.
Yes, ground the green wire in the RF harness. Don't do anything with the FAST EFI wiring yet. If I'm correct, you'll reconnect the EFI fan wire as you have it now. I just want to be sure the fan circuit is functional.
You may also need the key in the on position to get power to the gauge feed wire that is providing power at the switch.
Dave
CraigS
05-18-2020, 07:09 AM
Rick, Papa has a lot more experience w/ this efi system than I do so I can't really help much. My comment so far is I wouldn't bother w/ a light to indicate fan on. 13 yrs in my MkII w/ a temp sensor, fan relay, and a manual switch, and I have never felt I needed a light. Keep it simple.
Rick,
I agree with Craig on keeping it simple. I don't have either a manual switch or light for my fan and scan my gauges regularly while driving. If you want a switch and light, I'd wire it per the diagram I provided vs. how your harness is set up. Let's convince ourselves that the circuit works and you can decide from there.
Dave
Craig, I honestly agree, especially when you consider my level of understanding of things electrical!
Dave, Good to know that you opted to go with just the EFI trigger for the fan, without a switch or a light. If I can figure it out, I may forego the switch, and try to figure a way to put in the light. The visual would just help me feel comfortable.
I'm going to have to wait a couple of days to pursue this as I got a call, and construction in our area has restarted, and I have a warehouse to take care of tomorrow. I'll have to use today to get everything set up, and then we'll be at the job all day tomorrow.
Thanks guys.
Craig, I honestly agree, especially when you consider my level of understanding of things electrical!
Dave, Good to know that you opted to go with just the EFI trigger for the fan, without a switch or a light. If I can figure it out, I may forego the switch, and try to figure a way to put in the light. The visual would just help me feel comfortable.
I'm going to have to wait a couple of days to pursue this as I got a call, and construction in our area has restarted, and I have a warehouse to take care of tomorrow. I'll have to use today to get everything set up, and then we'll be at the job all day tomorrow.
Thanks guys.No worries, Rick. Just let me know if you need help when you get back to this. For reference, here is what I suspect we are dealing with in your fan circuit:
https://thefactoryfiveforum.com/attachment.php?attachmentid=128544&d=1589814739
The switch in your circuit is likely providing power to pin 86 on the relay (typical trigger). The green thermo switch wire is providing the ground on pin 85. It takes both to close the fan circuit and get power to pin 87 (blue wire). If all you want is a light, get a lamp and tap the blue fan power wire for the (+) side of the lamp and then ground the (-) side to any good ground. Any time the blue wire has power, the lamp will be on.
Dave
Thanks Dave. Looking at your diagram made me curious, so I went back AND READ what is in the wiring harness instructions! As you said, it's a switch, as they wired it into the harness, or the thermo switch, that typically gets hooked to the EFI or a thermostatic switch like the Painless. Sometimes my reading comprehension gets an "F" grade! I'll get back into this and start checking and correcting the issues.
I don't know what I'd do without these forums. I take my hat off to all the guys that built MK1's, when they had to figure all this out for themselves!
rich grsc
05-18-2020, 11:38 AM
If you want an in car fan switch, connect it in parallel with pin #85 and ground. If you want a fan on light, connect it in parallel to pin #87 and ground.
Thanks Rich. I'll take a look at doing that when I get the chance to work on it.
Rick,
To explain my original wiring diagram a bit more, it allows you to use a manual switch to turn the fan on if you want, regardless of what the EFI is doing. It will not shut the fan off if the EFI has triggered it on. The lamp only lights up if you are manually running the fan via the manual switch and will not illuminate if the switch is in the off position even if the fan is running via the EFI control.
If you just want a lamp on when the fan is on, then do as Rich and I recommend by running the lamp in parallel with the fan power (blue) wire off of pin 87.
Dave
chmhasy
05-18-2020, 01:12 PM
In the complete roadster manual rev 3T around page 229 it shows how to wire in the fan using the key so the fan does not run down the battery when the engine is shut off
Papa Dave, if you're out there, I disconnected the switch that I had installed per that segment of the wiring diagram that I posted. Apparently it's a one or the other situation, and I had it set up both ways. Not a good plan! Anyway, I cut the orange and two browns, and spliced the orange to the brown "gauge feed" wire, and abandoned the brown "switch feed" wire, and sealed off the end. I then traced the dark green "fan thermo switch" wire, which WAS connected to the "Fan 1" wire coming from the FAST computer. I plugged an extension wire into the dark green wire, and took it to a ground point, nothing. So I turned the ignition on, and took the dark green to ground, and still nothing. Is it possible that the engine needs to be running for that leg to have power? While I had the key on, I reset the fan control to more closely match the thermostat that is in the car.
So now I'm not exactly sure how to proceed. I'm thinking about tapping the blue wire that goes to the fan motor, and run it to a light where the fan switch was previously. If I can figure how to run a separate manual switch for the fan, that like you said, is not affected by the computer's operation of the fan, I may be able to use the old switch for both, since it has a light in the tip of the toggle. Not sure it can be used that way.
Well now I wait for the intake manifold gasket, that won't be here until the middle of next week, and hope and pray that I can get the thing sealed up properly this time. Like they say, fourth time's a charm! What will be interesting is if the leak in the intake manifold gasket was what was causing the idle to remain elevated when I had it running. I'm keeping my fingers crossed on that one, cause that would be the easy fix for that situation. If I do have to have the engine running to check the fan operation through the "fan thermo switch" wire, that will have to wait until then.
Rick,
I would have kept the two brown wires together. Looking at the harness schematic, the gauge feed wire looks like it is tapping off the switch feed and feeding your tach and speedo. If you trace the schematic for the dash harness, you see a brown gauge feed and brown fan switch feed pair coming into the harness together (both will have power) here. Follow the gauge feed wire and you see it routes to the small gauges. Trace the switch feed wire and you see it goes to the switch and ties into a second gauge feed wire that traces to the tach and speedo. What this means is that the two brown wires at the switch need to stay tied together or only the switch feed wire will have power. By not using the switch feed and tying it to the gauge feed wire, you have no power to the fan relay and won't have power to the tach and speedo gauges.
https://thefactoryfiveforum.com/attachment.php?attachmentid=128729&d=1590029445
Dave
Would that cause grounding the dark green fan thermo switch to not start the fan?
I can connect the fan switch brown wire in to the grouping, it was just what the ffr manual described doing with these wires if using the thermo switch, but then this manual is the last word in door stops. Starting on page 235 of rev. 3Q, it talks about cutting ground wires and reconnecting, but also shows the orange and two brown wires, and does not show the second brown being connected back into the harness. Not that I'm understanding much of this at this point. It takes me way too long to start to get the concept on alot of the electrical. Usually after it's too late to do anything.
Would that cause grounding the dark green fan thermo switch to not start the fan?
I can connect the fan switch brown wire in to the grouping, it was just what the ffr manual described doing with these wires if using the thermo switch, but then this manual is the last word in door stops. Starting on page 235 of rev. 3Q, it talks about cutting ground wires and reconnecting, but also shows the orange and two brown wires, and does not show the second brown being connected back into the harness. Not that I'm understanding much of this at this point. It takes me way too long to start to get the concept on alot of the electrical. Usually after it's too late to do anything.
Yes, because the fan relay has no power coming in on the (+) trigger (pin 86). The gauge feed wire you tied to the orange wire has no power when separated from the switch feed wire.
I must have been typing when you posted the edit. I thought that the cooling fan power came from the orange wire "cooling fan". The brown switch feed wire disappears when you go from the dash harness back to the main page where it onlys shows the brown gauge feed wire. Since the fan switch wire doesn't connect to the gauges, shouldn't they still be getting power? Now I've even lost myself on this!
I must have been typing when you posted the edit. I thought that the cooling fan power came from the orange wire "cooling fan". The brown switch feed wire disappears when you go from the dash harness back to the main page where it onlys shows the brown gauge feed wire. Since the fan switch wire doesn't connect to the gauges, shouldn't they still be getting power? Now I've even lost myself on this!
In the main harness, the brown gauge feed wire comes out of the fuse panel and gets routed to the dash harness. The orange fan power wire runs along with it, but gets it's power from the brown switch wire at the switch that you are removing. That orange wire provides power to the relay pin 86 (typical (+) trigger). The brown gauge feed wire that you connected the orange wire to has no power. It simply runs from the switch to the tach/speedo gauges. The only wire with power before they are all disconnected is the brown switch feed wire. When you connect all three together, the switch feed wire powers the orange fan relay wire and the brown gauge feed wire for your speedo/tach.
Once you've powered the relay for the fan, you just need to complete the ground to close the circuit. This is the green thermo switch wire. If the relay has power and this wire closes the ground, then power is sent to the fan via the blue fan power wire out of pin 87 in the relay. Would you like to continue this via a phone call? I'll be up for a another hour or so. I'll IM you my cell number...
Dave
Dave, wanted to let you know that you were correct. I connected the switch feed wire back into the orange cooling fan and brown gauge feed bundle, turned the key on, and grounded the dark green thermo switch lead, and the fan came on! So now, as long as the computer works, the fan should operate once the temp reaches 190. Can't thank you enough for the help, and your patience in getting me to understand what you were explaining!
Now it's on to my next disaster! The intake manifold gasket is supposed to arrive today, a week earlier than Summit said it would. If I can get this corrected, I might just have an operating go kart!
Rick,
It was a pleasure talking with you last evening. I'm happy we got it sorted out and you can move on to the intake without the distraction of the fan lingering out there.
Dave