Elec Fan Switch Mod

[Rohls]

The aux fan fuse should be at least 20A. They can pull ~19A on startup.

Will do...! Thanks.

[Rohls]

Alright, this is getting stupid and I'm getting frustrated...

 

I replaced the relay with the correct one (5 pin above), new fuses and everything seems legit.

 

Ground out the 'BLU/PNK wire and.....NOTHING happens. great. what am I missing?

 

What is the 'F12 splice'? I don't have any manual to reference...

 

Thanks,

[HOrnbrod]

The F12 splice is a 12V ignition switched junction point fused by PDC fuse F8.

 

You really need to invest in an FSM set for your 92. You can't troubleshoot effectively w/o the factory wiring diagrams.

[Rohls]

Thanks, yes, i should get a FSM. I have a Hayes repair manual, but it is junk.

 

Forgive me, but until I get a proper manual, where is Fuse 8? I looked at the PDC and couldn't find it... I under stand it's an ignition powered 12V....but which fuse in the PDC does it correlate to please? (ie...IOD, starter...etc). I took an image but can't upload it now.

 

Thanks....

[HOrnbrod]

It's the 60A blue maxi fuse, the one on the left looking down at the PDC. This is for a 91 - your 92 may be different. But that's not your problem.  If it was blown you would have a lot of other non-op electrical problems

[Rohls]

It's the 60A blue maxi fuse, the one on the left looking down at the PDC. This is for a 91 - your 92 may be different. But that's not your problem.  If it was blown you would have a lot of other non-op electrical problems

Thanks Hornbrod. understood.

 

i don't think I'm getting the 12V with the ignition turned on. It seems like both 85 and 86 are grounded with the key on. I'd like to retain mostly stock wiring; what wire/where would be the best option to safely tap into a 12V source for that leg of the relay coil? Could I jumper from the fuse you mention above?

 

And separately, do you think the fact that i don't have my A/C functioning is causing some issues? Like the A/C would send the 12V after the A/C relay is closed?

[HOrnbrod]

And separately, do you think the fact that i don't have my A/C functioning is causing some issues? Like the A/C would send the 12V after the A/C relay is closed?

 

This. I think you should get the aux fan working as it should before making modifications to it.

 

Just for grins, start it up and see if you have the 12V at the relay coil. Also all the relays up top are the same - so try swapping the aux fan relay with another if you haven't already done that.

 

[Rohls]

Thanks so much so sticking with me. I'm at work so can't check voltage right now, but last night I'm fairly certain I did not have voltage at the aux relay coil (85/86 pin) when the truck was running. Both the locations were at negative/grounded (?) potential (I concluded this by probing them independently to the battery positive terminal and noting +/- ~12V ) I think that's my issue...I'm not getting voltage there...however, I'll try again when I get a chance.

 

Here is an image of my current PDC. Yours is SO CLEAN :) Does it look like I'm missing something crucial?

[HOrnbrod]

You're missing the A/C relay (left side empty socket) and the ASR (Auto SHUTDONE-right side empty socket) relays. And I don't know WTH white relay you have in the aux fan fan slot. Get some correct relays in there from the junkyard and it just may work.

 

EDIT: Never mind the above. The 92 PDC is different than the 91 (of course!); the 92 is below. So you are missing the ABS pump relay (3rd slot from left, don't need) and the A/C relay (4th slot, need). Put a relay in the A/C slot and it might work.

 

[Rohls]

of course it has to be different :) I'll give it a try and report back. Thanks! :cheers:

 

And the white relay is a standard 5-pin relay from the local crap auto shop...granted it's an 'import'...but you know...in a pinch it might work...

[Rohls]

Success! I cut all the A/C wiring and relay out of the engine bay (nicely), pulled the positive from the aux fan to the 87 pin on the relay and it turned on!  :banana: 

 

I'm relieved and it looks cleaner in there too!

 

My lingering question would be what (I know, I should get a FSM...) color the wire on pin 87 on the AUX relay is so i can splice in there and not through the top of the fuse box...?

 

Thanks for all the help! . :MJ 1: .

[Minuit]

Just did this mod using a factory fog light switch in the cab and it works great. On my 91 it was exactly the same as the wiring diagram - ground out the blue/pink wire and the fan comes on as long as the key is on. Very easy and I would highly recommend, as my electric fan doesn't come on automatically until the temp is WAY too high for my liking.

[agamble]

Reviving this thread, electrical is not my strong suite. On my 89, the previous owner converted from the closed to open cooling system, the radiator that was purchased had threads for the temp. switch. The plastic tanks have started leaking so I ordered a CSF 2-core all metal, it lacks the thread port for the temp switch. I want to go the simpler route and add a manual switch in the cab, and this is where I am having trouble. Again a reminder, electrical is not my strong suite; I have read of what appears to me three different ways of accomplishing this.

 

Option 1 is following this info found at http://www.olypen.com/craigh/auxfan.htm :You can tap into your fuse box for a 12 volt source ** (you will have a choice of hot all the time, or ignition on, so you need to decide which you want to use), and run a wire from here to your switch. Then from your switch, you can run a wire to the Fan Relay. The Orange wire (pin 2) is the relay control wire (some models may be Yellow, but you won't have both), this is the one you want to tap into with the wire from your switch. There is enough slack here to easily use a press on wiretap, or a crimp on splice tap. 

This will not affect the automatic functions of the fan in any way, but will allow you to turn it on manually. 

 

Option 2: Locate the temperature switch and follow the wires back a couple inches. Use some push on wiretap connectors or any other prefered method to tap into the wires or if there is no more temperature switch just cut off the weather pack and solder the wires directly (would like the option of going back). Then run the wires into the cab and connect to the switch. 

 

Option 3: Wire 12v to one pole on your switch. Then take another lead from the other pole to the oragne wire on the elec fan relay. Splice the wire from the switch in with the orange wire. the orange wire is from the temp sender/computer that tells the relay to turn the fan on. If you supply 12v to this lead (very minimal power drawing--you can use small gauge wire) then the relay will switch turning the fan on. when the switch is off the temp sensor can still switch the relay one because the orange wire is still connected to the relay. Wire a toggle switch that will connect the the two wires together on the temp sensor on the radiator. That is all that sensor is, an on/off switch. Just tap onto those two wires with an on/off switch.

 

Options 1 and 3 appear to be the same, with a difference in 1 taps into the fuse box and 3 does not. Option 1 is the method I want to do, where I am struggling is how to tap the fuse box (I am assuming this is the fuse panel under the dash????), how to connect to the Orange wire on the fan relay. I am visual learner if any one has pictures of this setup, I could better visualize what is being said. 

[Eagle]

Reviving this thread, electrical is not my strong suite. On my 89, the previous owner converted from the closed to open cooling system, the radiator that was purchased had threads for the temp. switch. The plastic tanks have started leaking so I ordered a CSF 2-core all metal, it lacks the thread port for the temp switch. I want to go the simpler route and add a manual switch in the cab, and this is where I am having trouble. Again a reminder, electrical is not my strong suite; I have read of what appears to me three different ways of accomplishing this.

Let's keep it very simple. First, ignore the discussions above, since they pertain to the '91 and '92 HO models. Hornbrod mentioned somewhere in there that the Renix aux fan is controlled differently. That's key information.

 

That sensor that was supposed to thread into the tank of your radiator is nothing more than an ON-OFF switch. Below the preset temperature, the switch is open (off). When the coolant temperature in the tank reaches the preset limit, the switch closes and activates the relay, which in turn activates the fan.

 

Since you no longer have the bung in the radiator, you don't need to maintain that sensor/switch. Don't throw it away, but remove it and set it aside. Go to Auto Zone or Advance or NAPA and buy a new connector that matches the one on that radiator sensor. Attach wires to it, plug it into the harness where you removed the radiator tank sensor, then run the two wires to a toggle switch in your cab. It doesn't matter which way you connect the wires to the toggle switch -- it's all the 12-volt power to the control ("trigger") side of the relay.

 

Done.

[agamble]

Perfect, I felt I was making it more complicated than it needed to be. Thanks for the response took away a growing head from all the searching. In fact after a long search I found a post of yours on another thread where you had the same answer.

[Eagle]

 

 

i don't think I'm getting the 12V with the ignition turned on. It seems like both 85 and 86 are grounded with the key on.

 

 

This doesn't make sense. First (although the aux fan in the HOs seems to be an exception), the ground side normally isn't switched. Switches usually go on the "hot" (supply) side. Why/how would BOTH sides of a simple circuit be grounded, and why would they both be grounded only when the key is turned on?

 

How did you determine that both legs of 85 & 86 are grounded? Did you find that they are also both grounded with the ignition off?

[Eagle]

In fact after a long search I found a post of yours on another thread where you had the same answer.

 

Well, at least I'm consistent ...

[agamble]

 

Reviving this thread, electrical is not my strong suite. On my 89, the previous owner converted from the closed to open cooling system, the radiator that was purchased had threads for the temp. switch. The plastic tanks have started leaking so I ordered a CSF 2-core all metal, it lacks the thread port for the temp switch. I want to go the simpler route and add a manual switch in the cab, and this is where I am having trouble. Again a reminder, electrical is not my strong suite; I have read of what appears to me three different ways of accomplishing this.

Let's keep it very simple. First, ignore the discussions above, since they pertain to the '91 and '92 HO models. Hornbrod mentioned somewhere in there that the Renix aux fan is controlled differently. That's key information.

 

That sensor that was supposed to thread into the tank of your radiator is nothing more than an ON-OFF switch. Below the preset temperature, the switch is open (off). When the coolant temperature in the tank reaches the preset limit, the switch closes and activates the relay, which in turn activates the fan.

 

Since you no longer have the bung in the radiator, you don't need to maintain that sensor/switch. Don't throw it away, but remove it and set it aside. Go to Auto Zone or Advance or NAPA and buy a new connector that matches the one on that radiator sensor. Attach wires to it, plug it into the harness where you removed the radiator tank sensor, then run the two wires to a toggle switch in your cab. It doesn't matter which way you connect the wires to the toggle switch -- it's all the 12-volt power to the control ("trigger") side of the relay.

 

Done.

 

 

I got male connector that matches the female connector to the fan switch, attached new wires and ran them to a toggle switch. When I pluged the connector into the harness and flipped the toggle switch nothing happened, the fan would not come on. I thought maybe it was the fan motor but was able to jump it and it ran just fine. I recall that the fan should kick on when the A/C is turned on, when I moved the climate control knob to max A/C the fan never came on. Would these two things be tied together?

[Eagle]

 

 

Reviving this thread, electrical is not my strong suite. On my 89, the previous owner converted from the closed to open cooling system, the radiator that was purchased had threads for the temp. switch. The plastic tanks have started leaking so I ordered a CSF 2-core all metal, it lacks the thread port for the temp switch. I want to go the simpler route and add a manual switch in the cab, and this is where I am having trouble. Again a reminder, electrical is not my strong suite; I have read of what appears to me three different ways of accomplishing this.

Let's keep it very simple. First, ignore the discussions above, since they pertain to the '91 and '92 HO models. Hornbrod mentioned somewhere in there that the Renix aux fan is controlled differently. That's key information.

 

That sensor that was supposed to thread into the tank of your radiator is nothing more than an ON-OFF switch. Below the preset temperature, the switch is open (off). When the coolant temperature in the tank reaches the preset limit, the switch closes and activates the relay, which in turn activates the fan.

 

Since you no longer have the bung in the radiator, you don't need to maintain that sensor/switch. Don't throw it away, but remove it and set it aside. Go to Auto Zone or Advance or NAPA and buy a new connector that matches the one on that radiator sensor. Attach wires to it, plug it into the harness where you removed the radiator tank sensor, then run the two wires to a toggle switch in your cab. It doesn't matter which way you connect the wires to the toggle switch -- it's all the 12-volt power to the control ("trigger") side of the relay.

 

Done.

 

 

I got male connector that matches the female connector to the fan switch, attached new wires and ran them to a toggle switch. When I pluged the connector into the harness and flipped the toggle switch nothing happened, the fan would not come on. I thought maybe it was the fan motor but was able to jump it and it ran just fine. I recall that the fan should kick on when the A/C is turned on, when I moved the climate control knob to max A/C the fan never came on. Would these two things be tied together?

 

Yes, they would. Check to see if you're getting 12 volts to the fan circuit side of the fan relay.

 

When I bought my '88 MJ the aux fan didn't work at all -- which I didn't know until it overheated in stop-and-go traffic on a hot summer day. When I pulled the relay to check it -- two of the terminals broke off. There was so much corrosion that the relay was junk and the relay socket couldn't be salvaged. I cut the wires off the socket and wired individual terminals to each wire (didn't have a source for a replacement socket), plugged them all in, and it worked fine.

[agamble]

I am all for cutting an connecting directly to a relay if it will help with the issue, but before that route I would like to make sure I have tried all other avenues. I was able to get the fan on twice for about four seconds each time, but am unable to do so any more. Each time I had to disconnected the battery then reconnect. Once with the switch and second time was after removing the relay and cleaning the relay socket with an electronics cleaner. Would the fan diode be an underlying culprit for this?

[Eagle]

I am all for cutting an connecting directly to a relay if it will help with the issue, but before that route I would like to make sure I have tried all other avenues. I was able to get the fan on twice for about four seconds each time, but am unable to do so any more. Each time I had to disconnected the battery then reconnect. Once with the switch and second time was after removing the relay and cleaning the relay socket with an electronics cleaner. Would the fan diode be an underlying culprit for this?

I think you misunderstood. There is already a relay for the aux fan on the Renix XJs and MJs. I'm pretty sure there is no diode.

 

 

The photo is my '88 XJ. On the inside of the fender, just behind (above, in the photo) the coolant catch bottle, there's a relay. That's the relay for the aux fan. That's the relay I had to cut out and replace in the '88 MJ.

 

You probably don't have a catch bottle there. I added that when I dumped the factory plastic coolant bottle and converted to a Moroso aluminum surge tank.

[agamble]

I clearly misunderstood. Verifying that I am now on the same page as you, in replacing the relay socket, I simply cut the wires from the existing socket, solder on female connectors and attache to the appropriate post on a new relay. When replacing the relay do I want to use a 30 or 40 amp relay?

[Eagle]

The older fans supposedly only draw around 20 amps, so a 30-amp relay should be plenty. If you're buying a new one, though, why not go for the 40? FWIW, the fuse for the aux fan on my late wife's 2000 XJ is a 40-amp maxi-fuse.

[agamble]

Still not working, I spliced on all new connectors at the fan relay, tried three different relays, and I still cannot get the fan to come on at any given point. I know the fan motor works as had it running just an hour ago to make sure the motor was good. Is there something else that I missing that would cause the fan not work?

[HOrnbrod]

The below is the Renix kludge circuit for the aux. fan. :shake:  What a round-about way to turn on a fan. Anyhow, you want your new switch applying 12V at the cooling fan relay pin 2 (pin 85 on the relay). Try it and see if the fan runs.