Electric Fan not kicking in

[xj92]

My electric fan does not turn on when the engine gets hot. I've suspected this for a while, and I did some testing yesterday, and I couldn't get the electric fan to kick on. It's plugged in and connected. What sensor determines this, one of the temp ones? Does that sensor determine other stuff too, so I can see if it is working? At what temp should the electric fan turn on? TIA.

[CharlesS]

How did you test the fan motor ? Does it actually turn on when you apply electricity ? The sensor that is screwed into the thermostat housing energizes the relay for the fan. While you are at it..... check the fan relay too !!! I may be stuck and not allowing the fan to come on.

[xj92]

I just tested it by getting the temp up in the Jeep. I haven't tried rigging it up directly to electricity yet to see if the motor is bad.

[xj92]

I'll try what you suggested. Thanks.

[CharlesS]

I believe the cooling fan comes on about 215*, but I am not sure on the earlier model XJs.

[Hawaiian Style]

Electiric fan should come on at between 210 and 215. Not sure when Jeep changed it but the coolant temperature sensor for the 88 is located on the radiator on the driver's side. There's a relay that allows the electric fan to come on under 2 conditions... the temp exceeding 210-215 or whenever the A/C is on. If your Jeep is set up like mine check these components and you should find the problem.

While we're on the subject, looking at my wiring diagram for the Chief it looks like it is impossible for the electric fan to come on after the ignition is placed in the "off" position. I think I remember that mine used to come on after shuting it down though... After the engine rebuild and all the other stuff I had to do to keep the Chief on the road it doesn't anymore. Am I getting senile or did I mess something up?:confused:

[MACH90XJ]

xj92 ,Did you find a fix? my '90 is doing the same thing,turns on with ac but not at higher temp.Posting a solution you may have found would be appreciated.Thanks

[xj92]

I've been out of town for a couple days and haven't found a fix yet. I'll let you know what it was when I do. Mine doesn't come on with the A/C either though.

[5Cent]

Yes please post results. Mine quit working, along w/ my AC. I'm suspecting relays.

[ChiXJeff]

Originally posted by xj92
I've been out of town for a couple days and haven't found a fix yet. I'll let you know what it was when I do. Mine doesn't come on with the A/C either though.

I'm pretty sure that the electric fan should kick on when you turn on the A/C.

On a 93 (based on your sig) you've got 2 temp sensors. The one you DON'T need to worry about is on the top rear driver's side of the head, and it connects to the idiot light or the temp gauge. The other sensor is in the tstat gooseneck. This one is hooked up to the PCM, and controls electric fan, open/closed loop operation, etc.

If the electric fan isn't coming on with A/C, then I'd suspect fuse, relay or fan itself.

[truckeejeeper]

Whoa - is that right? The temp guage/idiot light sensor is on the drivers side of the head? I've been having problems with my guage and have only been messing with the sensor by the t-stat (new sensor, connector, etc.) Am I working in the wrong place?
BTW- I have replaced almost everything on my cooling sytem (w-pump, rad, t-stat, sensors, fluid.) and my electric fan almost NEVER comes on, except with A/C. I think it works fine, ie., my car doesn't get too hot to need it. I think it needs to get pretty hot to crank it on...?

- TJ

[ChiXJeff]

Minor caveat: I'm specifically talking about open, OBD-I 4.0ls. It may (or may not apply) to other models.

The sensor for the gauge and the sender for the idiot light are in the head, at the top rear driver's side. Single wire hookup (it grounds through the block) and you use a deep well socket.

The sensor for the PCM is on the front, in the tstat gooseneck.

TJ, you're describing normal operation of the electric fan. It's a supplemental, for when you need a little extra push, like high engine temp or running the A/C.

You can disconnect the sensor/sender at the rear of the head (NOT remove it!) without any ill effects; it's for display purposes only.

[Eagle]

Originally posted by truckeejeeper
Am I working in the wrong place?

Yes

[xj92]

Got it. I tested the fan and it worked fine, so I then went to the fuse. That was it. I guess I should have tried the easiest first :)

[5Cent]

Which fuse did you replace? The relay under the hood?

[xj92]

The 20 amp fuse in the fuse block under the hood. Little yellow blade fuse in with all of the big ones under the hood. When you pull the cover off of the fuse block it has a diagram. I believe it's labeled as Auxiliary Fan or Aux Fan.

[truckeejeeper]

Are those two sensors (t-stat neck & guage sensor) the same part#? I am pretty sure I have the engine you are speaking of., 1991 4.0l HO. I put the sensor I bought (idiot lite) into the t-stat housing. Is it working properly there? (I'm guessing no) Is it screwing up my cooling system? If the one I bought is called the "temp sensor" what is the one in the t-stat housing called? I know I'm getting off the main topic but since you guys are already on it... thanks.

[ChiXJeff]

Originally posted by truckeejeeper
Are those two sensors (t-stat neck & guage sensor) the same part#? I am pretty sure I have the engine you are speaking of., 1991 4.0l HO. I put the sensor I bought (idiot lite) into the t-stat housing. Is it working properly there? (I'm guessing no) Is it screwing up my cooling system? If the one I bought is called the "temp sensor" what is the one in the t-stat housing called? I know I'm getting off the main topic but since you guys are already on it... thanks.

I never can remember what year the change from closed to open cooling occurred. I was referring to the open system, which has a pressure cap on the radiator and an unpressurized overflow bottle. The earlier closed system has a pressurized bottle with a pressure cap, the radiator doesn't even have one to the best of my knowledge.

Come to think of it, I *KNOW* the PCM sensor will be different than the idiot light sender. The idiot light sender is a simple on/off that controls the light. The PCM sensor needs to know what the engine temp is to turn on the fan, go to closed loop mode, etc. so it's a ranging sensor.

Spent the last few minutes going through AutoZone's online parts...... apparently the PCM coolant sensor, the idiot light coolant sender, and the gauge coolant sensor are 3 different part numbers.

I don't know if it's "screwing up" your cooling system, but it for sure isn't doing you any favors.

As far as what to ask for: if you get asked "do you have gauges or idiot lights?" that one will be for the rear of the head. If you don't get asked that, it's *PROBABLY* the one for the PCM.

[MACH90XJ]

The reason I asked about fix was I heated it up good,just to bottom of redline and fan did not kick in and I remember when it would kick on before it got that hot.Mine is the closed system with sensor in the radiator and gauge sensor on head,since it is working with AC and not by tempature then I should be checking the sensor in radiator.Hey did I just solve my own problem :confused: Naaaa cant be that easy.

[5Cent]

Well, pulled 20mini fuse in box, still good, but replaced it anyways, no worky. Drove to autozone, borrowed 2 relays for fuse block for a/c and aux fan, still no worky. Any ideas? Neither have kicked on since this summer has started. I also noticed that on defrost, there is a hmming sound sometime from the vents when the fan is on low. I remember reading something about a vaccum line, correct? If this is the case, are the a/c and aux fan affected by vaccum lines also?

Adam

[Hawaiian Style]

I'm speaking from the '88 XJ perspective but if you've R&R'd the fuse and relay your problem is with the electric fan itself or with the wiring from the relay to the fan. As I posted earlier, there are two possiblities for the fan to come on.

1. AC on
2.Coolant temp reaches 210-215 range.

If your fan doesn't come on with the AC turned on then there's a problem somewhere in the wiring or the fan isn't working.

Test the fan itself (jump it with 12v) and then test the wiring from the relay to the fan. If that doesn't solve it then you'll have to go backwards from the relay which doesn't sound like much fun to me.... ;)

How hot is your XJ running? How hot have you seen the temp guage indicate this summer?

[5Cent]

Well, it's been running normal @ 210, hotter when idiling in traffic or going to the hunting spots, and it should be kicking on like it has before. This winter I had an overheating problem b/c I lost to much coolant. It was leaving alittle puddle every now and again,and I tried to say on top of it filling it up, but I got to far behind. A GDI/Modine along w/ everything else is in the near future when enough $ comes around. I noticed today that the "handle" part of the overflow bottle in the front is broken off. Any one got a pic of what it looks like. It looks like it's broken, but not for sure. There's lots of dirty and ugly coolant sitting in the bottom and no extra coolant has been dispersed into it in a long time. The fan and A/C worked great ever since this summer and I can't figure out why. How do I go about hooking it up straight to 12v? I'm not to good w/ electrical work, but i'll give anything a shot.

Adam

[xj92]

Just unplug the fan, and you'll notice it has 2 wires contained in a plug. Use some spare wire, and put one wire on the positive terminal of the battery, and the other on the negative terminal of the car battery (the other ends go into the plug, one each. If the fan starts spinning, it works. If it doesn't, the fan is the culprit.

[90red]

I also had that problem. But instead of trying to track down the problem, I just installed a switch so I could manually run it. I just took the male end of an old coolant temp sensor and cut it off and attached some wires to it. The male end plugs right up to the existing fan plug. One wire came from the fuse box (accessory slot so if i forgot to turn it off, when I shut down the jeep it also cuts off) to the switch, from the switch to the positive wire to the male adapter. the other to ground. didnt take long at all. mounted the switch in the open spaces in the dash. it runs real well. i also removed the clutch fan and installed a 10" elec. fan in place of it. i bought a new coolant reservoir, but its a real p o s. its aftermarket and not stealership. its obvious i will have to go stealership with this one. it doesnt hold pressure. she doesnt overheat very often, but i am forever losing coolant. sucks. oh well.

90red

[Hawaiian Style]

Stick with the set up on your XJ. Why mess with some switch you don't have to. I fixed mine and I am no great mech. Took some time and some effort but we're here to help you through the fix.

Jump the fan and see if it works and get back to us. This is not horribly complex so don't give up!

PS 90red, there's an afermarket setup that allows the use of a normal radiator cap at the pressure bottle by replacing it with some kind of racing presssure bottle- Aluminum I think. Search the threads for the conversion info. I haven't done it because my Chief is cooling like a champ but it sounds like a way better system to me. Those little Orings on the pressure bottle get old and tired and the system starts to lose efficiency with the stock setup.

[desertjeeper]

Originally posted by Hawaiian Style
PS 90red, there's an afermarket setup that allows the use of a normal radiator cap at the pressure bottle by replacing it with some kind of racing presssure bottle- Aluminum I think. Search the threads for the conversion info. I haven't done it because my Chief is cooling like a champ but it sounds like a way better system to me. Those little Orings on the pressure bottle get old and tired and the system starts to lose efficiency with the stock setup.

You can also get a pressure bottle out of a Grand Am, not sure what year, but they use a regular radiator cap and seem to be much more reliable than the Jeep part.

[90red]

Thanks guys. I will definitely look into that.

90red

[Rob Mayercik]

Originally posted by Hawaiian Style
PS 90red, there's an afermarket setup that allows the use of a normal radiator cap at the pressure bottle by replacing it with some kind of racing presssure bottle- Aluminum I think. Search the threads for the conversion info. I haven't done it because my Chief is cooling like a champ but it sounds like a way better system to me. Those little Orings on the pressure bottle get old and tired and the system starts to lose efficiency with the stock setup.

Just for everyone's edification, the aluminum overflow bottle is made by Moroso - search for that, and you'll turn something up.

IIRC, Eagle was one of the first (if not THE first) to do this, and from what I recall, he's pretty happy with it.

Rob