Jime

iTrader: (10)

I wanted to have manual control over the radiator fan so that I could run the fan manually, without the car or the ignition switch being on. I have always liked the way the VW's fan runs after you shut the car off to cool the engine down, but wanted to be able to control it myself so that when racing I could manually turn the fan on and leave it on while waiting in the lineup for the next pass.

This switch allows just that, manual control while the car is off in one position and normal operation in the other position.
You have to a DPDT (double pole, double throw) switch. DO NOT get one with center off.

The relay is located just in front of the battery. You will see them labelled Cooling Fan Relay 1, 2 & 3. We are only going to connect into Cooling Fan Relay 1, it is located in the lower right corner.

Remove the two screws holding the relay, remove the top cover and then the bottom cover so you have access to the wires beneath the relays. Turn it over and look for the wires under Cooling Fan Relay 1. You will see two small gauge wires (these are the control for the relay) and two larger wires. (these are connected directly to the fan motors)

The only two wires we are interested in are the G/Y (Green with yellow stripe) and the LG/R (Light green with red stripe). Cut both of these wire leaving enough wire on each end to strip and connect into. (Indicated by the white X on the picture)

Connect four lengths of wire (for each of the cut ends) approximately 6' in length (to reach inside the car). I soldered mine but you can just strip and wrap the wires together or use a connector. Make sure you label them so you can tell them apart when they are inside the cockpit. I used 18 gauge wire, this is only signal wire for the relay it does not power the fans. Probably could be even smaller but I like to err on the side of caution.

I used red wire for the G/Y connections and green wire for the LG/R connections. I put black tape around the two wires that came from the relay for identification (they connect to the center terminals of the switch). I used the grommet just above the fuel filter to get into the car.
Once inside the car just hook them up to the switch as shown in the picture.

The other two connections on the switch go to a +12 hot wire and the other to ground. I used the +12 wire going to the hazard switch and tapped into it.

I have my switch so that down is normal operation and up turns on the fans manually.

It sounds a lot more difficult than it is, the whole operation should take a maximum of one hour most of which is deciding where to come through the firewall and where to mount the switch.

It could also be wired for high speed operation but I decided that the normal speed was sufficient for my needs.

ejj

iTrader: (5)

Great writeup. I've been meaning to do this for a while, and just never got around to it. Have you tired it yet? Do you notice a drop it temps between runs?

Jime

iTrader: (10)

I have tried it, but not at the track. Pretty hard to tell how much it reduces temp because the gauge on the Max seems to stay in the same position (just below half) all the time. It sure blows hot air though so I am sure it is helping. Not sure how much circulation is going on once the thermostat closes though. It will circulate naturally with the pump off as long as the thermostat is open.

I am going to try it this weekend, its our second import race of the season.
http://www.importsociety.com/

They actually have a picture of my car (doing a VERY weak burnout) in the second page of the pictures from the 26 May event.

MardiGrasMax

iTrader: (14)

I have had mine wired with an underhood switch for a while. It seems to work very well. I leave it running all the time when at the track. If you pop your hood in the staging lanes it works even better.

JAIMECBR900

Thank you Jime. I'm going to try and do this before this weekend. I'm trying to make it back to the track on fri. night.

I vote they make this writeup a sticky.

njmaxseltd

iTrader: (19)

I think I read somewhere on here that you can accomplish the same thing by taking the A/C compressor fuse out and turning the A/C on. The compressor will not run, but the cooling fans come on. After your done at the track, put the fuse back in and your all set.

I think thats a bit easier then wiring up a relay or a switch.

Jime

iTrader: (10)

I tried that, only one LITTLE problem, it doesn't work unless the car is running. If your car is running you are just keeping it hot so it defeats the whole purpose of the cooling fans.

BBaker025

iTrader: (1)

GrEaT wRiTe Up MaN!

JAIMECBR900

Does the car have to be running or just the key on? Cause it would be the same with just the key on.

Jime

iTrader: (10)

Car has to be running for the fuse thing to work. Actually you have to pull the relay. Its a good idea for when you are driving back on the return road etc, just doesn't work unless car is running. Believe me I tried all the tricks I could before resorting to adding a switch. I even started a thread asking if anyone had done it.

xHypex

iTrader: (1)

That was a nice write-up Jime I wired mine up today, but I used wiretaps instead of cutting the wires. I would have soldered, but the fit was kinda tight. By using wiretaps you can also use a SPDT instead of a DPDT switch (or buy a DPDT and only use one set of the connectors). I also placed the switch inside the relay box so that I didn't have to run wires all the way inside the car. Then I can just flip the switch before getting back in the car.
Either way I had never thought of this mod before your post so thanks for the idea
-hype

mzmtg

iTrader: (11)

I added it to the FAQ.

Awesome write up!

Jime

iTrader: (10)

I was going with the SPDT originally and not cut the wires but didn't want to take a chance of messing up the ECM so decided to isolate from it completely.
The switch I wanted in the car because I want to turn it on at the end of the run and have it cooling while coming back the return lane. Some days our run offs come pretty close together so want to get as much cooling as possible.

Toolrocks

iTrader: (1)

A friend pointed me to this thread - great write up. I may do this as well. I was just gonna add that the few times I've raced my car at the track I run my heater on full blast too. Thinking that it will help remove heat from the cooling system and therefor, the engine.

Jime

iTrader: (10)

100% correct, not having the A/C on at the track makes it hot but the heater is #$%&*. However it does work. I know one guy who puts the heater on to warm up his bottle, the line is long enough to leave it connected and still watch the gauge. When it gets up to temp he just puts it back in the holder.

PS Also watch how long you leave the fans on for, I left mine on for about 45 mins and forgot about them and drained the battery. I also was running the bottle heater so pretty large drain. Felt sort of stupid getting a boost in the staging lanes.

xHypex

iTrader: (1)

Jime does your fuel pump start when you turn on your fans? Mine does and some of the lights on the gauge cluster also turn on. It's not a big deal, but I try to be careful not to dump too much fuel into the engine on startup.
I haven't run the fans at the track yet, but would you say anything over ~30 mins without running the car would drain the battery a good deal? I guess I'll just see how it works and if it's worth it, and if I kill my battery I can always do a push start
-hype

Jime

iTrader: (10)

Nothing should come on but the fans if you hooked it up like my diagram. It must be where you got your +12V from. I took mine from the flasher plug +12V but you could take it from the lighter etc. The lighter would only allow the fans to start when the ignition switch is on accessories.
Gotta be something funny in your hookup, there is nothing that should make the fuel pump or gauge lights come on.

Check out you wiring again.
Jim

xHypex

iTrader: (1)

I tapped my 12v from a wire that already runs from my battery (it used to run to my old fogs), so that shouldn't affect anything. I used the same two wires in your diagram, but I didn't cut them; I only tapped into them. Either way I hardly use the fans so it's not a big deal. I probably won't bother rewiring it, but the idea was still a good one
-hype

Toolrocks

iTrader: (1)

Since you didn't cut the wires or diode isolate them, you're sending 12 volts back to anything else that gets powered by that circuit. That could possibly be a bad thing. Not sure though. I know it's a pain to redo something but I'd probably re-wire it. Good luck.

phatmax95

iTrader: (29)

I have a few questions regarding the writeup.

How will I know the switch is a DPDT?
Can I use a regular switch and wire it differently?

I cut the two wires and add a 6' section to each end, correct?

From what I gather, the switch has 4 connections.
1 comes from the +12
1 comes from the ground
1 comes from the LG/R wire closest to the relay
1 comes from the G/Y wire closest to the relay

Now, the other two wires that are loose (the wires farthest from the relay that were cut)... Where do they go?

They look like they both tie into the G/Y wire? I dont know so help me on that part.

Also, can I just connect the +12 and ground wire straight from the battery to the switch, or from the battery to a grounded screw? ( and not the hazards or whatever he did?)

Thanks alot..

Toolrocks

iTrader: (1)

Buy a switch that says it is DPDT (it will be on the packaging, or have the person at the store help you)
You could use a regular switch but that would complicate things tremendously - you'd need to wire in a relay or diode isolate blah, blah, blah
Just buy the recommended switch and wire it up exactly as the diagram shows. There is a total of 6 connections. A DPTH swich will have 6 posts on the back of it. These posts are in two groups of 3. In each of the 3 post groups there is 1 post that is connected to another post, in that group, when the switch is in one posistion. When you flip the switch into the other position, the post will then "switch" from the post it was connected to, to the other post within that 3 post group. I hope that makes some sense. Refer to the picture on the first thread.

So the wiring would actually be:
1> +12 Volts
2> Ground
3> G/Y to the switch
4> G/Y to the switch (yes another wire)
5> LG/R to the switch
6> LG/R to the switch (hope you got it by now)

Hope this helps. Good luck.
Yes, you could directly hook it up to the battery but, make sure you put a fuse in that line close to the battery.

phatmax95

iTrader: (29)

Well. I wired it all up and it works great.. great idea too, btw. If I had known that the switch had 6 posts, then I would have understood the picture. And about that fuse near the battery.. is that just to protect the switch? If I do get one, which rating should it be? Thanks again.

Toolrocks

iTrader: (1)

Glad to hear it is working for you. Fuses are primarily used to protect the power source and circuit from further damage. If the wire from the battery to the switch were to get grounded, it would possibly discharge your battery completely or, more likely, burn the insulation off the wire the entire length back to the battery and ignite anything else it may be touching. You can use a simple in-line 10amp fuse. That is the rating of the fuse used to protect the factory circuit, so use that. Good luck.

phatmax95

iTrader: (29)

Thanks for all your help. I'll run out tomorrow and buy a fuse to throw on there.

Jime

iTrader: (10)

I revised this mod in the spring when I got the 95 but just never got around to posting it. Aaron was kicking my butt this weekend so I though I would post it.

All that is necessary is to ground pin #13 of the ECU for High Speed and pin #14 for low speed. Just connect to the wire by soldering etc, it is not necessary to cut, you must leave the original circuit connected.

You can do either one or both. You will need just a simple on-off (spst single pole single throw) switch for one and an on-off-on (spdt single pole double throw) for both.

Almost any switch size can be used it is signal only, no current. All the ECU does when fans are required is to ground either one of these pins so you cannot do the ECU any harm either.

The fans will come on when the ignition switch is on, with the car on or off, but will not run when the ignition is off. I ran down the battery once last year by forgetting about it with ignition off when it was wired according to the original method I wrote up.

Hardly any wire is required and can also be of any size, plus you are just running from the ecu to switch, I mounted mine on the ecu cover so only needed a couple of inches of wire.

Aaron92SE

iTrader: (128)

Woohoo! Thank you so much Jim for looking out for us. Now, I am going to make this work on my VE.

SXN

so tap to 13 for high speed, and 14 for low speed... run them to either side of a metal switch, the center off is completely off, and either side is high and low? sounds good, and easier, thanks Jime, you were already on the how to forum for this mod, and rightfully still are

*edit*
Im a little confused on this wiring once im checking out my haynes manual (page 12-26 if that helps out)... wire 13 seems to be connected to the "fuel pump control module" and wire 14 seems to hook up to "rt. front heated oxygen sensor"... am i totally off here? I dont want to do this horribly wrong, or mess up my ECU, so any insight?

Jime

iTrader: (10)

If you go by the colour of the wires indicated in the picture you can't go wrong, (LG & LG/R, should be Light green and light green/red) if you look at the Haynes they indicate a totally different colour. I have the Haynes manual too, but the FSM is much clearer and IMO more accurate than Haynes. That Haynes electrical circuit drawing is pretty confusing at best in comparison. I would look at the FSM for the 98 though just to make sure because that pic I did is from the 97, however my 95 was exactly the same.

PS You can see on the pic I posted the pinout of the ECM quite clearly.

SXN

so do you cut the wires by the ECU itself... light green and green wires on the ecu wiring harness? guess there is only one way to find out any idea if the wiring colors changed for the year 98?

Jime

iTrader: (10)

You know its so easy to understand something when you write it, but for the poor bugger reading its a bit different.

No cutting required just solder etc to original wire and leave it connected in order for the fans to work normally.

PS Thanks for pointing that out, I amended my instruction post too.

SXN

couldnt you technically leave the switch in the off position and it would complete the circuit?... if you just soldered to the original lead, wouldnt current still flow through the wire, even if you grounded it with a switch?

Jime

iTrader: (10)

Leaving the switch in the off position does complete the circuit and its works as per normal. Its only when you turn the switch to either on position that the circuit is grounded and the low or hi fan speed is initiated.

There is really no current flowing through the wire it is just open and when its grounded the fans start. Not sure if that explains it but best I can do. It is either grounded manually by you or by the computer when it senses high engine temp.

SXN

i understand, did you strip a section of the each wire and solder to that, or solder directly to the original point where the wire connects? I understand the idea of how to do it, but im not sure how grounding it would work, because it seems like the signal could still reach its destination... is the ground the past of least resistance or is it disrupting the signal? i would love to have a factory service manual, but am trying to make due with a haynes. I believe i found what your talking about, two wires going to the cooling fans, but theyre marked as light green, and light green with red... even more confusing. thanks for the help

Jime

iTrader: (10)

Yes just strip the wire and solder to it. I screwed up again and went back and corrected it. The manual is correct it is LG and LG/R, which of course is Light Green and Light Green / Red.

Ok here is how it works, if you look at the pic of the circuit it shows those two wires connected to the ECM ie pins #14 and #13. If you look at where they are connected they are the grounding circuit of the signal wire for a relay. There is already power connected to the other end ie Pin #14 is connected to pin #2 of cooling fan relay-1. The other end of that relay signal is already connected to 12v via pin #1 of the relay the G/Y wire. So all that is required to complete the circuit is to ground the LG/R wire, that is what you are doing with the switch and that is what the ECM is doing when it receives the signal that the engine requires cooling.

Did I explain that ok? Any time you ground pin 14 or 13 with the ignition turned on you are going to activate the lo or hi cooling fan because you are grounding or completing the circuit to ground that is already connected to 12 volts via the other end of the relay.

Jim

SXN

i gotcha now, and glad i cleared up the color issue, now i can do this mod with some confidence! thanks Jim

Jime

iTrader: (10)

I am just a little thick some days, a combo of old age and senility. Glad I have some young blood to keep me on my toes and thanks for correcting me on the wire colours.

The FSM is a great tool for some of my hair brained schemes I have just enough electronic/electric knowlege to make me dangerous. Spent about 15 years in Amateur Radio which really helped me understand a lot of that electronic stuff.

SXN

yea...im 17 so it helps to have someone with wisdom help me out. I was more worried that my haynes manual was yanking my chain than you were wrong. I have some eletrical knowledge (my dads a master electrician...but i dont want to ask him how to change anything on my car) atleast enough to put neons and stereos in a couple cars. thanks for the help Jim

Ninos_Maxima

iTrader: (5)

What would help is if you get those special radiator fans that spray water to, Ive seen them on some Hondas

Jime

iTrader: (10)

The fan running on hi speed in combo with a 180 deg thermostat works great and you can do them both for free, well you do need a switch.

My temp runs in the 185 deg area all the time at the track.

SXN

How are for cars running high high temps, they use them on intercoolers too, fan with a water spray to keep it cold. cool feature, little harder to integrate