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I am tired of my coolant getting bubbling hot and that wonderful electric fan never "automatically" kicking on. Have any of you connected it to a toggle switch and if so, are there any tricks to it (such as fuses needed) other than just connecting a power source, ground, and the fan wire to the switch? I've got a '93 XJ.
I did that conversion from olypen and it works great. I was suprised to see the light comes on, on my switch even when the temp sender automatically turns the fan on. Easy mod to!!!
part # TX-43 for the Coolant temp sensor...its 18.00 for it from
carquest
Or you can put a relay and fuse on the fender wall like I did and hook it up inside the main fuse block to a fuse that comes on with the key, and the fan hooked to fuse on fender wall hooked up on battery.
I am clueless when it comes to electrical terms. What is a relay exactly? I went out to dink around with it tonight and found that when I turn the AC on, it kicked the fan on as well, so it is working. The Jeep was cold at the time. But, when I was out on Saturday and I overheated, the fan was not running. I was running the vent on cool, but not the AC. Is the fan activated only when the AC or the defrost is running? Will a new Coolant temp. sensor allow it to respond better? If I tried to connect it to a switch I know I would mess something up.
The part # is for the coolent temp sensor and it is the stock sensor that kicks the electric fan on when it is suposed to come on. If the fan comes on with the a/c, then it is defenitly the sensor toasted. A relay is an electric on/off switch. It has the normal hot and ground leads, then it has an other set of hot and ground leads that magneticly control the switch. There are 2 types, normaly open and normaly closed. The normal open will stay off until it gets a 12v hot and then it will close (turning on) and the normal closed is on until given a hot feed, then it turns off.
Doing the toggle switch means finding a hole in the fire wall to run your wire through to the fan, which means in some cases.......drill one.
But those are your options......unless you don't do anything (not good)
The sencor is not the one that gives you the read out on the dash for the temp. It is for the ecu to fan.
A relay is used to switch higher-draw devices, allowing you to keep the main flow of power as short as possible. You would use the toggle switch to make the relay turn on/off, and the relay would turn the fan on/off. It sounds like more work (and is, a little) but is the better and more correct way to solve the problem and will help keep you from having to fix it later.
Have someone check the FSM for around then - there should already be a relay, and you can wire a switch in parallel as an "override" to turn the fan on at will. There are two controls to do this already - the Thermal Fan Switch and the A/C Request signal from the panel. They are in parallel, which means only one needs to happen for the fan to come on (unlike serial, where EVERYTHING would need to happen!) When you add the switch, you simply change it from an either/or to an either/or/or - giving the fan a third way to be turned on.
Since a very small power signal is used to drive a relay, getting the switch in is simply a matter of finding which wire to energise (or ground) and making that happen thru the switch. I'd be surprised if there is no relay - especially if the fan signal is driven off the ECM!
A relay is used to switch higher-draw devices, allowing you to keep the main flow of power as short as possible. You would use the toggle switch to make the relay turn on/off, and the relay would turn the fan on/off. It sounds like more work (and is, a little) but is the better and more correct way to solve the problem and will help keep you from having to fix it later.
Have someone check the FSM for around then - there should already be a relay, and you can wire a switch in parallel as an "override" to turn the fan on at will. There are two controls to do this already - the Thermal Fan Switch and the A/C Request signal from the panel. They are in parallel, which means only one needs to happen for the fan to come on (unlike serial, where EVERYTHING would need to happen!) When you add the switch, you simply change it from an either/or to an either/or/or - giving the fan a third way to be turned on.
Since a very small power signal is used to drive a relay, getting the switch in is simply a matter of finding which wire to energise (or ground) and making that happen thru the switch. I'd be surprised if there is no relay - especially if the fan signal is driven off the ECM!
I'm going through the same problem right now. The ECU is supposed to turn the fan on at 218* or when the AC is on. To me, 218* is too late to kick in the fan. I'm installing a flex-a-lite 110 to replace the clutch fan and will wire the stock elec fan to the new flex-a-lite and put both on a toggle, so they go on at the same time. Sounds like yours only goes on w/AC. You can snip off the connector on the fan-side. The black wire is hot (+). Buy a relay and it should tell you how to hook it up to a switch. It's easy, but I'm terrible at electrical and find it non-intuitive. The good news is you only have 4 relay connectors to worry about. Your clutch fan may be bad, too if you're overheating.
The standard Hella/Bosch relay is rated for 30A nominal, and is overkill for anything you are likely to use it on. Ask for a "Bosch-Style" relay at your local, and it should cost you no more than $10 (here in the SF Bay Area, I pay about $8 - for reference)
Terminal diagram for the relay is on the side of the case, and all are numbered.
I am clueless when it comes to electrical terms. What is a relay exactly? I went out to dink around with it tonight and found that when I turn the AC on, it kicked the fan on as well, so it is working. The Jeep was cold at the time. But, when I was out on Saturday and I overheated, the fan was not running. I was running the vent on cool, but not the AC. Is the fan activated only when the AC or the defrost is running? Will a new Coolant temp. sensor allow it to respond better? If I tried to connect it to a switch I know I would mess something up.
XJ91 -- you do not need a relay. The relay is already there.
5-90 -- the '91 and newer do not have a thermal switch in the radiator tank like your Renix-era XJs. Beginning in '91 Chrysler used the PCM to control the aux fan. The PCM takes the temp data feed from the sensor in the thermostat housing and uses that data to decide when to activate the aux fan. It also uses this data as part of the injection and ignition controls, so if that sensor is toast the engine probably isn't running well.
Someone within the past couple of weeks posted a very elegant way to rig a manual override switch for the aux fan while isolating it from the PCM to prevent backfeed problems when controlling the fan manually. This is not a problem with the Renix models because the aux fan is a stand-alone circuit, but from '91 and up feeding 12 volts at the fan relay will also feed 12 volts back into the PCM -- which may not be a good thing.
On my '96 model the aux fan relay is switched to ground. This means that the relay is always hot and the switch is on the ground side of the circuit. I added a wire that goes from the ground side of the relay control to a switch that I mounted next to the rear window defrost and from there to a good ground under the dash. One of the best (and cheapest) mods I've done.
Beginning in '91 Chrysler used the PCM to control the aux fan. The PCM takes the temp data feed from the sensor in the thermostat housing and uses that data to decide when to activate the aux fan. It also uses this data as part of the injection and ignition controls, so if that sensor is toast the engine probably isn't running well.
Well I'll be d****d! I was browsing this thread about switches, when this comment from Eagle jumped out at me. This comment takes us off topic and into the vexed issue of overheating. I had a mysterious overheating problem in my 93 XJ - it ran hot on freeways in summer when heavily loaded, but was fine in traffic. I changed the fan clutch, but wasn't sure this was the cause of the problem. Much later, I checked the fault codes when diagnosing another problem, and got a code which said the engine was running too cool (possible coolant temp sensor problem?).
Eagle's comment is the missing piece in my jigsaw: if the sensor was/is giving a falsely low temp reading, then the PCM thinks the engine is running cool, AND the aux fan doesn't switch on. Looks as if a replacement coolant temp sensor will solve my problem.
Amazing how useful forums can be, even when it's only by coincidence....
