2003 Ford Focus, Runs Hot, Cooling Fans Inop, Part 1

This 2003 Ford Focus came in with the complaint that the car was running hot. It has a 2.0 liter engine and is a non SVT model. Although similar to later model vehicles with the same set up, this year is unique in it’s wiring harness design. After asking multiple questions of the owner and doing some basic inspection I found that the coolant was not boiling over but the temperature gauge was reading quite high. After determining that the cooling fans would come on at high speed at a temperature of 250 degrees, I decide to start investigating the low speed fan operation and started with checking the low speed fan relay. It is the light gray square relay in the center of the picture.

After removing the relay I found that the center plastic was slightly melted. Close inspection found that the terminal was not fully seated and had been making a poor connection, hence the heat damage.

Time to open up the box and see what is going on. I started by removing the intake breather tube and air filter cover. Then I could access the 7 mm headed screw to the left of the fuse box in the following picture.

Next, I released the holding clips on the opposite end of the fuse box.

After separating the retaining clips that held the two halves of the box together I was able to see inside the rear of the fuse box. The wiring looked pretty good so I decided to push the wire back into place and see what I had.

The terminal pushed back into place without too much effort so I knew there was a chance it would be usable.

To confirm the terminal was okay I inserted a jumper wire and tested the terminals drag resistance. It was okay.

I installed a new relay and held the wire in place with my pliers to make sure it would not back off.

If I had to I could have cut,spliced and moved all of the wiring to the empty relay cavity but that is a huge amount of work and everything currently is okay.

On to confirming the repair. Well things are not going so well. The temperature is up to 238 degrees and the low speed fan has been commanded on but the fans themselves are not on.

Now the engine is up to 244 degrees and the medium speed has been commanded on and still no fans on.

Now we are up to 250 degrees and the high speed fan fans have been commanded on and the fans are finally on. This is what I had originally discovered in testing earlier. My guess now is that the relay and wiring problem I had found earlier had probably been caused by some one else testing and they had pushed the terminal in and not corrected the condition.

I did find out what the original problem was and I will post about it tomorrow. The following picture is where the gauge should be normally when the the low speed fan comes on.

This is just a pet peeve of mine and has nothing to do with the repair but here it is. The air filter had obviously been replaced. Why did the installer not clean the dirt out of the air filter box? It takes about what 30 seconds to vacuum out the dirt with a shop vacuum? It just bugs me!

To see part 2 of this repair please click here.

9 discussions on “2003 Ford Focus, Runs Hot, Cooling Fans Inop, Part 1”

  1. Code P0128 generally refers to a problem with the engine not warming up quick enough. The most common cause is an open or weak thermostat. If you decide to replace the thermostat make sure that use use a factory temperature rated replacement. I prefer OEM.

  2. W
    I have a 2003 ford focus ztec with the check engine light on. Auto zone did a diagnostic and said it came up with code PO128 which they said was a cooling system problem….but here is my problem. Car guage says it is running at normal temp. Coolant level a bit low in the reservoir…but should not be low enough to activate sensors. Both fans are running well..so I would probably rule out temp. Sensor. Not sure where to go from here but I have to drive through the desert tomorrow at 108 degrees. What do I check next????? Please help. Linds

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