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89 XJ electric fan not turning on, but works with A/C

R

Renegade XJ

NAXJA Forum User
Location
corona ca
Just like the title says, I have an '89 XJ 4.0 renix, looks like the previous owner switched over the electric fan from a newer XJ (10 blade). It works perfect with the A/C on, but it doesn't turn on with the A/C off. At what temp should the fan turn on? And what controls it? I was on the trail over the weekend and my temp was about 240 or more and the fan still wouldn't kick on. I ran the A/C for the rest of the day after finding that it worked like that, and it never got close to getting hot after.
 
On the lower left side of the radiator there is a bung hole (about an inch in diameter) with a thermal switch in it. Wires go up and through a two wire connector, then to the fan relay, the same relay the A/C actuates.

The thermal switch can go bad, the connector can come unplugged. Less likely is the power to one of the wires is interrupted, it came off the relay, or is chaffed etc..

I piggy backed (spliced) two wires onto the two wires coming up from the thermal switch, ran them into the cab and wired them up to a toggle switch. I turn my aux fan on when the temperature starts to creep up (at the gauge), before it gets hot.

Pretty simple really, the thermal switch closes the circuit when the thermal switch closes, just like a toggle switch. and completes the circuit to actuate the relay. Power into the thermal switch ( yellow wire form the ignition switch) and when it closes it supplies power to close relay. The A/C splices into the same wire going from the thermal switch to the relay.

The thermal switches are problematic anyway, they close IMO at too high of a temperature. What your gauge is showing you is happening at the top rear of the head and what temperature the thermal switch is closing is happening on the lower left side of your radiator. What is happening at the lower left of your radiator is one of the coolest places in the system, what is happening on the top rear of the head is one of the hotter places in the system. They say the thermal switch closes around 209 degrees, the ones I tested closed closer to 220 F, though my test may have been a bit flawed.
 
8Mud said:
On the lower left side of the radiator there is a bung hole (about an inch in diameter) with a thermal switch in it. Wires go up and through a two wire connector, then to the fan relay, the same relay the A/C actuates.

The thermal switch can go bad, the connector can come unplugged. Less likely is the power to one of the wires is interrupted, it came off the relay, or is chaffed etc..

I piggy backed (spliced) two wires onto the two wires coming up from the thermal switch, ran them into the cab and wired them up to a toggle switch. I turn my aux fan on when the temperature starts to creep up (at the gauge), before it gets hot.

Pretty simple really, the thermal switch closes the circuit when the thermal switch closes, just like a toggle switch. and completes the circuit to actuate the relay. Power into the thermal switch ( yellow wire form the ignition switch) and when it closes it supplies power to close relay. The A/C splices into the same wire going from the thermal switch to the relay.

The thermal switches are problematic anyway, they close IMO at too high of a temperature. What your gauge is showing you is happening at the top rear of the head and what temperature the thermal switch is closing is happening on the lower left side of your radiator. What is happening at the lower left of your radiator is one of the coolest places in the system, what is happening on the top rear of the head is one of the hotter places in the system. They say the thermal switch closes around 209 degrees, the ones I tested closed closer to 220 F, though my test may have been a bit flawed.
Click to expand...

I have an in-cab toggle switch as well. BUT - If you forget to check it or if other people drive your jeep you are screwed.

You can also get an aftermarket temp sensor switch thingy that you can (insert) into the radiator fans anywhere you want, like at the front of the system and it has a rheostat where you can dial it to come on when you want. They are only like $20 at autozone but they always went out on me when mud would get into the circuitry box.
 
BleepinJeep has a good point. Without going into all the whys and wherefores, I installed a Hayden unit (~$38 @ O'Reilly) 41/2 years ago. Set to come on at 195* with probe in the radiator fins. Has worked flawlessly, mud not being a problem aside from the occasional dirt dauber nest, and relatively easy to install.
 
The switch I installed, is tied into the ignition circuit and the power goes out when the motor is off. It is push pull and has a large lighted face. It lights up red when the fan is on. An aftermarket Hella driving light switch, a little pricey but they last a lifetime. http://www.hella.com/produktion/Hel..._Pull_Switch/Illuminated_Push_Pull_Switch.jsp

Putting an external thermostat in for the fan is a good idea, I've just never tripped across any that I was happy with yet, most don't look like they are very water resistant. I tried looking through the Kixon catalog, that is one thick catalog. :)
 
The OEM Renix thermal switch closes at 185 degrees and opens at 170 degrees. I have measured a couple of them and uses one to turn my electric cooling fans.

As mentioned earlier, check the wireing between the relay and the switch in the radiator. You could also test the integrety of the wires by unpluging them from the radiator and useing a loop wire between the two connectors on the plug. That would remove the switch from the system but test everything else. If every thing else is good, the fan should run.
 
ok, Thanks for the advice however I think mine is different. The previous owner also changed the cooling system over to an open loop system. So I think my thermal switch is located at the water pump/thermostat housing.

Can somebody tell me which relay is for the electric fan?

I also read somewhere that if I let the engine heat up and then unplug the connector to the thermo switch my fan should kick on.....well it didnt. What does this mean? bad relay? Again, it works with my A/C....
 
Renegade XJ said:
ok, Thanks for the advice however I think mine is different. The previous owner also changed the cooling system over to an open loop system. So I think my thermal switch is located at the water pump/thermostat housing.

Can somebody tell me which relay is for the electric fan?

I also read somewhere that if I let the engine heat up and then unplug the connector to the thermo switch my fan should kick on.....well it didnt. What does this mean? bad relay? Again, it works with my A/C....
Click to expand...

My XJ's are '94 and '96 which are different to both the Renx and the later 2000+ XJ's so I am not in a position too say exactly how they work. However, I do know that if you unplug the wires to the temperature sensor (CTS) on the Renix, the fan will not come on. Also, if the radiator was changed to an open style, then all bets are off. You will have to say exactly what you have so that you could get proper help. Start with the temperature switch for the fan,...Is it an after market switch or is it a resistor type OEM sensor. You may have to get an after market temperature switch and wire it to the relay.
 
Put your switch in a pot of water on the stove along with a candy (or whatever) thermometer. Set your meter to ohms and attach to the sensor leads. Heat and see at what temperature the switch closes. Or rig up a simple test light with a battery and bulb if you don't have a meter. This is a quick and simple way to confirm what you have. If the resistance slowly changes as the temperature rises, you have the wrong type of sensor.

And, if the fan turns on with the A/C, the relay is okay.
 
Note from DJ

Let’s see if I can explain some of the mystery of the temperature sensing devices involved with the Renix system.

There are a total of four different temperature sensing devices in all.

The first two are the coolant and manifold air temperature sensors. They are temperature to resistance converting sensors which are used by the ECU to control different operations related to engine management.

The coolant temper sensor was originally located in the side of the block below the intake and exhaust manifold and the MAT sensor should be located on the back side of the throttle body screwed into the intake manifold. These two sensors are covered by the table in the link in my prier post. Now if the previous owner moved the location of the coolant temp sensor to the thermostat housing they should have unplugged the original wiring from the original CTS position and extended the connections up to its new location and reconnected them there.

Temperature sensor number three will be located at the back corner of the next to the firewall and the bake booster and the master cylinder. This sensor is used for transmitting information to the instrument cluster for either a gauge or hot engine light.

Number four is the one in question hear it was originally screwed into the engine side of the radiator on the driver side below the upper radiator hose.

Here is the information regarding this sensor.
NOTE: it is simply an ON-OFF switch which controlled the cooling fan relay.

Electric Cooling Fan
An electric cooling fan in addition to the engine drive fan is used on vehicles equipped with air conditioning or heavy cooling. Normal operation of the fan is controlled by the coolant temperature through a radiator mounted temperature switch. It will also operate whenever the A/C clutch is activated regardless of coolant temperature.

When the engine coolant temperature is below approximately 190*F or [88*C] the radiator switch is open and will not allow battery voltage to the cooling fan relay. The fan does not operate because the relay contacts are open. When the coolant temperature reaches approximately 190*F or [80*C] the radiator switch closes and allows battery voltage from the ignition switch to reach the relay coil and to ground, thus energizing the relay and allowing battery voltage to the cooling fan motor.

If A/C is selected regardless of coolant temperature, the ECU provides a ground for the A/C relay coil. With the A/C relay coil energized, the circuit is closed from battery voltage to the A/C clutch and to the engine cooling fan relay. Since the engine cooling fan relay has a permanent ground, the relay is energized and battery voltage is applied to the engine cooling fan motor from the ignition switch.

So if the previous owner was trying to use a resistance sensor to control the coolant fan relay, it will not work on the Renix system.

I hope this information helps, please keep us posted as to your progress or if you need more info.
 
8Mud said:
The switch I installed, is tied into the ignition circuit and the power goes out when the motor is off. It is push pull and has a large lighted face. It lights up red when the fan is on. An aftermarket Hella driving light switch, a little pricey but they last a lifetime. http://www.hella.com/produktion/Hel..._Pull_Switch/Illuminated_Push_Pull_Switch.jsp

Putting an external thermostat in for the fan is a good idea, I've just never tripped across any that I was happy with yet, most don't look like they are very water resistant. I tried looking through the Kixon catalog, that is one thick catalog. :)
Click to expand...

I did the open system swap on my 90, and I just ended up cutting the wires off the sensor in my old radiator and wire-nutting them together. Plugged that back into the harness. Fan comes on with ignition. You could run this setup back to a toggle on the dash instead of hard wiring it on. I might do this in the winter. I figure for the next several months i'd rather just have that fan on. Seems to warm up plenty fast... very consistent ~195 degrees.
 
Nice write up you got there djgrayXJ. Detailed and idiot proof. For me, that is Renix cooling 101.
 
djgrayxj said:


So if the previous owner was trying to use a resistance sensor to control the coolant fan relay, it will not work on the Renix system.
Click to expand...

This is where a lot of people go wrong including myself. Since the radiator temp switch doesn't fit into the thermostat housing, many people who convert to the open system go to the parts store and try to find a switch to fit in the housing that will come on at 210 or so.... but this doesn't work because its not the right kind of switch. it just ends up acting like a very expensive thermostat housing plug!
 
BleepinJeep said:
This is where a lot of people go wrong including myself. Since the radiator temp switch doesn't fit into the thermostat housing, many people who convert to the open system go to the parts store and try to find a switch to fit in the housing that will come on at 210 or so.... but this doesn't work because its not the right kind of switch. it just ends up acting like a very expensive thermostat housing plug!
Click to expand...

The answer is likely right here someplace, http://www.sensata.com/klixon/thermostat-precision.htm

5-90 or somebody who is good with catalogs, could likely find a couple of good possibilities here. I'm old as dirt and my eyes give me problems after ten minutes or so. An applicable thermal switch could be ordered form any refrigeration place.
 
Great info guys, I don't have my XJ infront of my right now but I do remember seeing that the wire that is plugged into the thermostat housing leads itself over by the drive side headlight/below the air filter box. I'm going to get on it Sat. So I will keep you guys posted.
 
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