Electric fan switch question

I am planning on installing an aux. fan switch in my 98 to help cool the engine down. I read a really good writeup on projectxj.com, but the only thing he didnt include was circuit protection. I want to install a fuse to protect the circuit, anyone put a fuse in with this mod? What amp. rating did you use?

with my stock fan i have a 20amp in there and it runs perfect and hasent blown it...

That set up on projectxj.com looks pretty getto for a perment set up. If you want to do it right so you don't have any problems with it. Use quality connectors, and a heavy duty relay. You need a relay rated for 40A at least, a heavy duty water proof fuse holder and 10AWG wiring for the high current side of the relay. As far as the switch, and the wiring into the cabin it's not to important as to the guage of the wire as long as you fuse it correctly.

Here are some links to Del City A good sorce for automotive wiring hard parts.

Heavy duty water resistant fuse holder.
It's only rated for 30A, but I,ve been using one for a while now without any problems.

Heavy duty SPDT 40/50A relay with socket.
I have found it's better to run a relay socket in the engine bay where it's a harsh enviroment.

Good crimpable terminals.
If you use these you're going to need a good crimper. Not one of those cheep auto parts store things. Get one like this. Ratching crimper. I have the bottom one. As far as the terminals go you'll need 12/10AWG (yellow) butt connectors, 12/10AWG ring termanal 8 stud IIRC, 16/14AWG push on terminals. Other wise solder every thing, and use heat shrink tubing to seal the jont. You're also going to need 10AWG wire, and I normally use 14AWG, or 20AWG for all my switch wiring, and usually just buy that from Auto Zone.

Starting at the PDC's main battery post (under the little cover). Use a ring terminal to connect the fuse holder. Butt splice the 10AWG wire to the other end of the fuse holder, and run it around to a location near the factory plug for the fan.
Now what you want to do is cut the power wire to the fan (I would cut before the plug so if you ever have to replace your fan you won't have to disasemble your wiring). Run the Factory power wire to terminal 87a on the SPDT relay. The new 10AWG wire will go to the 87 termanal, and the fan side of the power wire will go to termanal 30. (This will allow the NC (normaly closed) contacts in the relay to pass current to the fan for factory operation.) Connect termanal 86 to a ground, and 85 will go to your switch inside. A good place to get power from inside is either the cigerett lighter (switched), or the power port (not switched). As long as you use 14AWG wire for your switch wire to the relay the 20A fuses already protecting those circuits will be safe, but if you use a smaller size wire I would add an inline fuse to protect it.

87a- OEM power wire.
87 - New 10 AWG wire from battery.
30 - Power wire to the fan.
86 - Ground.
85 - Switch.

Oh, and unlike was mentioned above you will need a 40A fuse. A 20A will pop in time. I was using 20A's until I could get my hands on some 40A ones, and kept popping them. You might want to order those too. They're kind of hard to find unless you have a Car Audio shop locally. Also if you're lucky enough to have a Grangers Supply retail store locally. Thats where I get my crimp shrink termanals, but Del City prices are a little better.

PS I'm working on a timer circuit that will run the fan for a while after you shut the key off to help with the heat soak problem on our later model XJ's.

EDIT: If you drill a hole to run the switch wire into the cabin don't forget to use a grommit on it so the wire dosn't chafe, and short out.

scoobyxj said:

Oh, and unlike was mentioned above you will need a 40A fuse. A 20A will pop in time. I was using 20A's until I could get my hands on some 40A ones, and kept popping them. You might want to order those too. They're kind of hard to find unless you have a Car Audio shop locally. Also if you're lucky enough to have a Grangers Supply retail store locally.

Click to expand...

Thanks for that info scoobyxj. The 20A fuse is fine for the pre-1996 straight bladed aux fans - never blew in my 91MJ. When I swapped in a new curved blade aux fan from a 2000 model, it ate up the 20A fuses. Then went to a 30amp fuse and all is well. BTW, what is the 1999-2001 aux fan fuse amp rating?

Thanks

Here's one designed for a '97 plus XJ and wiring diagram.

http://www.soxja.org/forum/viewtopic.php?t=575

Here is a safer way to do th relay. This way you do not have to bring power wires into the passanger area. And a plus is the switch will last longer because the ground circiut will not heat up the switch like a power wire will. Think about it. How many of us have melted a switch before. This wiring will fix that issue. Just do not forget to fuse the 12 volt power wire going to the relay.

magimerlin said:

Here is a safer way to do th relay. This way you do not have to bring power wires into the passanger area. And a plus is the switch will last longer because the ground circiut will not heat up the switch like a power wire will. Think about it. How many of us have melted a switch before. This wiring will fix that issue. Just do not forget to fuse the 12 volt power wire going to the relay.

Click to expand...

Exactly what this link covers

http://www.soxja.org/forum/viewtopic.php?t=575

comanche91 said:

Thanks for that info scoobyxj. The 20A fuse is fine for the pre-1996 straight bladed aux fans - never blew in my 91MJ. When I swapped in a new curved blade aux fan from a 2000 model, it ate up the 20A fuses. Then went to a 30amp fuse and all is well. BTW, what is the 1999-2001 aux fan fuse amp rating? Thanks

Click to expand...

Thanks for the wireing schematics, but I just need to know what the 99-01 Owners Manual lists for the aux fan fuse rating in the PDC. 30A?

rstarch345 said:

Exactly what this link covers

http://www.soxja.org/forum/viewtopic.php?t=575

Click to expand...

Look more carefully at there pic. Its not exactly what that link covers. There is power (12volts) going to there switch. In my setup there is only ground at the switch. I am only switching the ground on and off for the relay not the power like they are. The only reason there is a ground on there switch is because it is a lighted switch, and they state that it s a lighted switch as well. My way is just a safer way to wire things when a wire has to be brought inside. As stated befor a switch that is wired with power will heat up. And after a period of time can and will be able to start a fire. The way mine are done the switch cannot get hot as there is no power getting to it just the ground. Hence no chance of a fire. I would rather not have an accessory on(like a fan) and go into a store and come out to see
:flame::flame::flame::flame:

www.waytekwire.com has the rocker switches that ARB uses and fitchVA (naxja member) has one of the best write ups for adding accesory switches and relay wirring.

Fitch's page: http://fitchva.com/jeep/

His page is one of the best naxja member pages, it's definately worth your time.