Fan not coming on

[CREWZIN]

When the water is hot (without the AC on) the engine Coolant Temperature Sensor is the information sensor for the Powertrain Control Module (PCM) which turns the fan on. The AC overrides the sensor and the fan comes on on matter what temperature the water is.

If your fan doesn't come on when the water is hot your problem is either the sensor, PCM or one speed of the fan which works when the AC is off.

[TheAnt]

Originally Posted by CREWZIN

OK, the picture below is what the fuse box looks like in the engine compartment (only it's 180 degree backwards). The Number #5 fuse (40 amp) is for the fan.

Thanks guys I have been wrestlin' with this too. Like you say you can swap say the horn relay for the high speed fan. I pulled he slow relay and cleaned the contacts. I installed it without the cap to be sure it engaged with the engine running.

What I found with my intermittent problem is that if I reach in when the fan is not turning and nudge the outside ring on the blade just a bit, it starts.

That indicates a bad winding or maybe brush contacts, I guess, depending on how the motor is made.

BTW DO NOT reach in there and try turning the fan if YOU ARE NOT 100% sure it is NOT TURNING!!! A nylon tie-wrap put in the right location can help because you can harldy see the fan if it is on.

In my case it would pretty much always stop where I could see a blade not moving.

Looks like fan motor to me, the whole assembly looks to be over $300

[CREWZIN]

Ant,

Don't emember seeing you before so WELCOME to the forum.

If you let the dealer do the whole job it probably is $300 or more, especially with the labor rate. The fan housing with motor can be picked up for around $100 or less but I read form someone on the forum that you can now buy the motor itself at auto stores which would make it even cheaper. Of course you still have to take the fan housing and old motor out to replace the fan as there's very little room to work in there.

All in all, I say to get the housing out the first time is about 1 1/2 hours. I could probably do it now in about 1 hour. One of the worse parts is the cross member in front of the radiator, a real PITA as there's absolutely no room to get at the bolts to hold it on.

[TheAnt]

Originally Posted by CREWZIN

Ant,

Don't emember seeing you before so WELCOME to the forum.

If you let the dealer do the whole job it probably is $300 or more, especially with the labor rate. The fan housing with motor can be picked up for around $100 or less but I read form someone on the forum that you can now buy the motor itself at auto stores which would make it even cheaper. Of course you still have to take the fan housing and old motor out to replace the fan as there's very little room to work in there.

All in all, I say to get the housing out the first time is about 1 1/2 hours. I could probably do it now in about 1 hour. One of the worse parts is the cross member in front of the radiator, a real PITA as there's absolutely no room to get at the bolts to hold it on.

I guess I'm in for that. Today's trip to work had temp going up on the open road so it looks like a bad fan AND thermostat.

I saw $109 for the fan shroud assembly and about the same for a motor at O'Really and Autozone, same pic of motor.

I can't afford the $100 for the motor until the 20th so I will try to clean it and maybe free up or turn over brushes. The thermostat is 6-13 doallars and I can handle that.

[TheAnt]

Oh, sorry for my lack of etiquette! Thanks for the welcome! I *thought* I had posted before but it was likely another forum.

Did I see something in AlldataDIY about removing part of the intake manifold (cover?) to replace the thermostat? If so what a yuk!

I just got through $660 change of timing belt and a while you have it down, water pump. It was more than I cared to get into so I had a trusted mechanic do it! That of course makes one wonder about infant mortality when the engine gets hot.

An observation here too. I cooled the engine, opened the radiator and could see the thermostat straight down, I think on the discharge side of the water pump. Ordinarily I would watch the water heat up and begin to slowly flow as the thermostat opens. Fortuantely, I didn't have my head over it when it started apparently boiling out. I couldn't tell whether the water pump was pushing through a quickly opening thermostat (I guess quickly) or pressure from the boiling was feeding back from the other side. Either way I think I have a bad thermostat because it overheats under highway speeds.

Another thing. This is the first time I ever saw that running the heater would do enough to cool the engine back to normal! I guess I am used to cast iron V-8s...

[CREWZIN]

Ant,

Yes, unfortunately you have to take the upper manifold off to change the thermostat. There's a new guide to follow to help you with taking off the upper manifold....

Spark Plug Guide

There's very few of us that will actually take on the job of changing the timing belt and you did the right thing by changing the water pump. Was the tensioner for the serpentine belt mentioned by the mechanic. That's another thing that might want to be changed especially if you have an 01 or 02 model since Chrysler changed the tensioner in 2003.

[TheAnt]

Thanks for the SPG link, great stuff!

The mechanic said (without my prompting) that he checked the belt tensioner and it was OK. I hope so.

One thing I have noticed is a grinding sort of noise that sounds like it comes from somewhere on top of the engine. It is like a water pump when the pulley bearing is shot. It may be unrelated. I hope so. I will listen to my son's motor for comparison.

What about the gaskets on the intake, EGR, etc? Should they be replaced?

[CREWZIN]

Ant,

Noise is hard to diagnose over the internet. Good luck in finding it.

The gaskets on the upper manifold can be reused a couple of times. Not the Thermostat gasket (but the new T should come with a new gasket).

On the EGR pipe ...you didn't say what year your PT is. The EGR only came on the 01 and maybe 02 engines. After that Chrysler found away of doing without it. If you do have it, it's the hardest part of taking off the upper manifold. The bolts (2 of them with two different sizes; 8mm and 10 mm I think) are in an awkward place to get at and the gasket can be reused on that too.

[kwmcook]

Hello, Crewzin. I appreciate the forum. My 2002 Cruiser has just started intermittent overheating, too, and, after changing the thermostat and the coolant temperature sensor (after which my engine light came on), I've been stumped. My fan comes on when the coolant comes up to temperature while idling, then goes off and stays off. My Chilton's says that the Powertrain Control Module turns the fan on either fast of slow depending on inputs from the VSS or ECT, without immeditely referencing the meanings of those initials. I found VSS was the vehicle speed sensor, but the ect remains a mystery. I'm still stumped, but this and other similar threads, some dating back to 2003, have given me a little more light and hope. Thanks.

[CREWZIN]

On the VSS, the PT needs no fan running after 35 miles per hour. There's enough air blowing thru the radiator to keep things cool. I found that out myself when the fan motor burnt out in Orlando, 90 miles from home and my PT overheated and blew out all the coolant out the overflow bottle. I put some plain water in and made it back to the turnpike and went the entire 90 miles back home because I never had to come to a stop.

On the ECT I found this:
"The ECT (Engine Coolant Temperature) sensor provides an input to the PCM (Powertrain Control Module).... The ECT sensor provides input for various PCM operations. The PCM uses the input to control air-fuel mixture, timing, and radiator fan on/off times. The PCM uses ECT sensor input to end messages over the PCI bus for temperature gauge operation."



As far as your problem, I think the high speed part of the motor on the fan is burnt out (my guess) because your fan comes on when the temperature raises at idle then you said it goes off. It's probably the low speed that your seeing and when it's time for the high speed to come on, it doesn't. There is a high sped relay in the fuse box in the engine compartment. You can try changing that for a cost effective first try before going for a new fan and housing or new fan motor. Again, that's only my guess at your problem.