Change fan relays and still over heating 2002 RT10

[Tim]

I have replaced both Fan Relays in my 2002 RT10 and it is still over heating. On the hi way there is no problem as there is enough air flowing to keep it cool. In town while stopped you can hear the fan is not coming on and it will pin the temp gauge in a few minutes if I don’t park it or get it onto the hi way to flow more air. The fan will work ok for an hour or then it will quit for an hour or so. Turning on the air conditioner does not kick the fan in when it is acting up and but when it is working the a/c will engage the fan. I can turn the fan by hand and it seems to be turning freely with no noise. Can I by pass the fan to manually keep it running to confirm that the problem may be in the fan motor or does some one have other suggestions?

Thanks

Tim

 

[Tom F&L GoR]

This sounds silly, but make sure you are filled with coolant. The PCM has it's own temperature sensor (and it is not the same sensor as used for the gauge) and if it is below water level, it won't read properly. (I have Gen 1, so not exactly sure where Gen 2 sensor is.) Could be that when it gets "dry" it thinks it's not hot.

At idle, water pump speed is lower so it may not push liquid onto the sensor like it does when at highway speed. That may explain the air-flow response; it might be an engine speed response.

Similarly, perhaps the symptoms are caused by a bad sensor. As referred to above, just looking at the temp gauge won't tell you if this is true or not.

If you have access to a good OBD-11 reader, it can show you other sensor outputs. You could verying that the temp gauge is correct when it indicates high temps. Maybe it's not?

The relays get an 18 gauge 12V from the key and the PCM provides grounds to close. You can permanently ground the wire leading to the PCM (one relay has yellow, one has blue/pink)and the fan will run whenever the engine is on. You have to ground both to run on high speed because they are in series.

Good luck.

 

[Tim]

Hello Tom,

Yes I have confirmed that it is full of fluid and that the system has been burped and there is no air in the system. I am confident the thermostat is working as that is confirmed from driving on the hi way and the temp drops to normal.

I have tried different engines speeds in case it is the water pump but I don’t think this is the problem but maybe?

I am confident that the gauge is correct as this is my 2nd Viper and at out side air temps in the mid 90’s and in stop and go traffic the fan always ran almost continually.

Yes I think a sensor is probably the problem or it may be the fan motor it self.

On grounding this do I go right to the PCM and tap into those wires and ground them there or can I do it from the relays themselves and if so what prong do I tap into?

Thanks

Tim

 

[Tom F&L GoR]

You can ground wherever is most convenient.

The fan-on relay wire to PCM ground is C27 20DB/PK, or circuit C27, 20 gauge, dark blue with pink stripe. The low/hi relay wire is C137 20YL (yellow.)

You have to ground leaving the relay, not ground the PCM.

If it's like Gen 1, then the relays are on the front of the passenger footbox and the PCM is on the side of the passenger footbox. I think Gen 2 PCM is on the drivers side and don't know where the relays are.

If this is not helping, I'll email the circuit from the service manual. See my profile for address. Have to step out now, too, sorry.

 

[Steve-Indy]

Agree with Tom...might also worry about the known 2001 (and a few 2002's) water pump impeller problem. You might turn your heater on to see if it seems normal in operation on a steady basis while your temp jumps around...just a thought.

 

[Tim]

Yes, my heater is working fine. I have been using it to help disapate the heat when the fan is not kicking in and it is boiling me out of the car.

I checked the connections and they all seem tight but who knows until I can get it on a hoist and get a meter on it.

Thanks

Tim

 

[Tom F&L GoR]

This may help.

Larger one in my gallery.

 

[Tom F&L GoR]

Tim, check your email please.

 

[Tim]

I have, thanks

Tim

 

[Tim]

Re: Change fan relays and still over heating 2002 RT10 It was the fan

It was the wiring harness on the fan.

Fixed for now with a new fan module on the way.

Thanks for everyones help

Tim