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post #1 of 8 (permalink) Old 10-03-2002, 07:33 PM Thread Starter
 
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Over Heating Solved :)

Greetings All,

OK, Finally fixed the damn overheating problem! Just for the sake of archiving this so I can remember how I did it 5 years from now, here's the details.

Wife's 97 intrepid was overheating during stop-n-go traffic with A/C on, or while idleing for long periods of time. If A/C turned off, motor would cool right down.

The culprit was a defective passenger's side cooling fan motor.

Here's the details on the wiring scheme used probably on all 1st generation Intrepids.

The wireing harness has a single three wire plug near the center bottom of the radiator. This plug has a Ground, +12v for the low speed circuit, and +12v for the high speed circuit.

The single 3 wire pig tail, plugs into a 'module' at the center bottom of the radiator. This 'module' is nothing more than a dumb junction box with apparently no electronics inside.

From the module a single three wire harness head off to the passenger side fan, and single 2 wire harness heads to the driver's side fan.

The driver's side fan is just a simple single speed 12v motor attached to ground and the +12v High speed wire from the main wiring harness.

The passenger side fan is a Two speed fan, having two seperate coils for Low and High speed modes, and attaches to all three wires (gnd, +12v low spd, +12v High spd) from the main wiring harness.

During high speed fan operation, both fans get 12v on the high speed wire from the main wiring harness (Low speed wire is off)

During Low speed operation, Dodge did kind of a neat trick. Only the Passenger fan receives power from the low speed wire on the main harness. However, since a DC motor can also be used as a DC generator, and since the low speed coil of the passenger fan is energized, the high speed coil of the passenger fan works like a generator. Since the High speed wire is attached to each of the two fan motors, the passenger side fan works as a DC motor AND a DC generator The result is during low speed, the passenger fan provides power to the driver's side fan, and both run!

In my case, the Passenger side fan High speed coil was dead (Bad armeture brush), resulting in only the Passenger side fan running at low speed, and the Driver's side running at high speed.

Bottom line, if one fan is running and the other isn't, something broke!

Sorry about the long post, and hope this helps someone in the future!
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post #2 of 8 (permalink) Old 10-04-2002, 12:31 AM
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that is seriously good troubleshooting. i'm sure this will help some people in the future. great work.
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post #3 of 8 (permalink) Old 10-04-2002, 01:02 AM
 
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Thank you for the in-depth problem solving.

you guys are Intrepid Gods!
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post #4 of 8 (permalink) Old 10-04-2002, 01:22 AM
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Cool

Good job, great thread.
I assume you replaced the fan motor or had a refurb put in?
What's your temp at now for saying's sake?

AHHH! risk of flurries! (shoots self)
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post #5 of 8 (permalink) Old 10-04-2002, 04:42 AM Thread Starter
 
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Yea, I just replaced the fan motor itself. The options were:

$340us for a complete fan shroud unit & both fans,

$170us for just the passenger side fan motor.

With ambient temp runing about 85F, the motor runs at a comfy 200F with AC on, With AC off, fans kick in at ~225F and turn off around ~212F. I have yet to get them to kick in at HIGH speed just idleing now OH, and the A/C is noticibly cooler at the vents now resulting from decent air flow over the condensing coil.

BTW, Temp data was recorded using an OBDII -> laptop dongle from www.OBD-2.com (pretty nifty item!)

James
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post #6 of 8 (permalink) Old 10-04-2002, 01:13 PM
 
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So when the fans come on both should run at all times? Is there ever a time when only one of the fans is running? Thanks.
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post #7 of 8 (permalink) Old 10-04-2002, 03:12 PM Thread Starter
 
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Unless they changed something for my '97 model, or the 3.3 motor, They both should always be running!

Its physically impossible for only one motor to run without something being broken (at least on my yr/model!)
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post #8 of 8 (permalink) Old 10-04-2002, 04:57 PM
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On another not, i find your web site very interesting.
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