Look @ the resistors connector also. I have fix this issue on 3 of my 6 zx3's Iv own over the years. 2 of them just needed the resistor, & the third one I ended up replacing the fan assembly because it kept burning up the new connector. There are a lot of threads on this problem, do a search for more info on overheating in traffic. This is the Motorcraft part # on the pigtail replacement connector. "4U2Z-14S411-DA"

 

My `01 overheats the same way, took it to Ford and a wire going to the fan assembly looked fried. So they replaced the $400 part and its still does not work. Wanted the cruise fixed in the same visit SO, I was charged for 2 diagnoses, the part, and labor to install. Nearly $800 - NO FIX, Now they think its the PCM which controls guess what, the fans and the cruise. They said further fees would be waived to check things out. I need to give the car back to them for completion. some day......

 

Ok, and we'll assume that the fuses are good since one fan is working. You might want to look in your owner's manual anyway as I do believe there are 2 fuses for the fans. Do you have an electrical tester? If so, you can remove the resistor, and test it using the Ohms setting. That will tell you if there is something wrong with the resistor before you replace it.

 

Sorry, yes the fuses are good and yes there are two of them. I do have a multimeter, but how would I go about testing the ohms on the resistor? What kind of numbers am I looking for? I've only used this tool for measuring voltage.

 

No more than an ohm or two. If your meter shows kilohms or megohms your resistor is no good. If it's supposed to drop the voltage by, say 5 volts at 5 amps, then the resistance would be 1 ohm.

 

Useful answer, but before this thread takes off again I'll mention that the question was asked 7 yrs. ago.

Computer access lets you see more info. on the posters and the questions, including date/time of each post.

 

X2. He's in the Bahamas, it takes a while for wi-fi to get there...................

 

My 2001 Ford Focus Zetec SE 1.6L petrol with a/c overheated recently. The safety facility worked well and the engine started firing on two cylinders. That warned me that something was wrong and I noticed the temperature gauge was in the red region. I pulled over and saw that the coolant was low, so I added water. I was able to get home without the gauge going high again, but to cut a long story short, I found several faults: a burst heater hose, a burnt contact on the fan resistor connector, the left hand fan motor defective and the thermostat not opening properly! (Is this a record?) There was an engine overheat fault displaying. It disappeared after disconnecting the battery.
I blocked off the heater since I couldn't find the proper hoses, I ordered a thermostat and ran the car without one (not a serious problem as it is hot here), I bridged the connector to eliminate the burnt contact, and replaced the left hand fan with a generic one. I replaced the thermostat the other day and was surprised to find the car overheating again. Removing it and testing it alongside the old one revealed that the new one was only opening to about 5mm, just as the old one had done when I tested it previously. Now, however, the old one was opening to a good centimetre. It seems the new one was defective! I'm back to running without the thermostat - which seems to have affected the fuel consumption somewhat - it's down from about 40 mpg to about 37 mpg. I have also confirmed that the fans are not coming on as expected. I normally run with the air conditioner on, and that causes the fans to come on, which helps with radiator cooling, but on idling without the air conditioning on the engine overheats but the fans do not come on. Both relays seem to be operating normally: removing either one affects the fan speed when the air conditioning is on, and removing both cuts off the fans entirely. Shorting contacts 3 & 5 on the relays causes both fans to come on as expected. Testing outside the vehicles shows that the relays are working properly. All fuses are OK. The temperature sensor (situated in the cylinder head) does not seem to be the problem - connecting my tablet via a dongle shows the temperature behaving as one would expect and the engine slows down normally on warm up. Under normal running the temperature stabilises to about 80 to 90C. (The original and replacement thermostats open at 82C. I don't believe that they are two-stage types.)
So, I am stumped! Why aren't the fans coming on at high temperature? Could it be a problem with the computer (PCM)? It seems unlikely, since everything else seems to work normally. Perhaps a bad contact somewhere? That seems unlikely since the fans come on as expected when the a/c operates. Any suggestions?

 

When you don't fix stuff then you will find 5 things wrong every time you look. All that stuff did NOT go bad at the same time.

No generic fan on the planet will output nearly so much air as the dedicated OEM fan can.

You must pretty much cut any melted area out of the resistor connector, simply 'bridging' it may not do spit. The wire is often melted one inch either way and BOTH sides.

With all parts made in China now a bad new stat is no surprise at all. Look up inside stat hole and see if there is any plastic pieces stacked up from them cracking off the housing gasket wall, common. The pieces can lock the stat action up.

Blocking the heater makes any overheat worse, the heater can get rid of some of it if stat sticks shut.

If failsafe cooling came on then sometimes engine has already blown a head gasket by then. Driver supposed to catch overheating before that.

 

Need more info., fan operation temps are in the 100-110*C area.

 

Thanks for the input. Doubtless the fan and connector had failed sometime before but I had not noticed because the fans also operate with the air conditioner (which is always on), and control any incipient overheating. I agree that my maintenance has not been up to standard and that the generic fan is not very good, but it's the best I can do here, and it seems to be satisfactory under the conditions we have - no long distances, no high speeds. Possibly the overheating caused the thermostat to fail, though it is not clear at what stage the hose burst. If the wires had been melted as you say, I would have noticed and dealt with that - I wasn't born yesterday! LOL. The bridge is effective. There was no debris in the thermostat housing, but there may be some elsewhere - a good point. After disconnecting the temperature sensor and starting the engine, the fans run at low power for a moment, after a short delay, and then at high power. I believe this is the default condition and perhaps suggests that the computer is not at fault. The problem may be the sensor. I am currently investigating that possibility further.

 

The fans work on low with a/c on and then go to high if needed. Both of mine are like that.

The generic fan kills you at LOW speed, the fans are not even on commonly at high speeds.

Don't be too sure about the resistor, commonly you cannot see any melting at all from the outside, only pulling it apart shows the connectors themselves, the wire further back can be melted inside the insulation. BTDT. X-ray vision? I commonly change the 6 inches before the resistor. If your bridge only plugged into same connector size then still an issue, that connector is the smallest one anywhere in that circuit and why it melts. Undersized by the excellent engineers at Ford like their battery cables to make you buy parts. I upgrade to non-plug in any longer but positive screw connections big enough to never melt again. I do NOT buy a new resistor, it simply melts again, the connection has to be made bigger to carry the amp there. Look at the connectors at back of fan shroud that carry the exact same power, they are 40% bigger.

 

Thanks. It's strange the connector to the resistor was the one that was burned. Obviously that circuit would be carrying much less current than some of the other circuits. Anyhow that circuit is not the problem at the moment: it carries current to the resistor without introducing any appreciable resistance of its own. I don't quite get your point about wires melting under the insulation: the insulation melts at a far lower temperature than the metal of the wires. When we say a connector is "burned" we mean that corrosion has occurred, causing poor contact, leading to local heating which in turn increases corrosion and destroys surrounding insulation. Eventually contact is lost completely. The problem is localised to the connector.

 

You can have increased resistance in wire that has gotten hot without any evidence of melting externally on the insulation, it has a shielding effect up until melting point depending on how thick the insulation is. I say that after more than 40 years of cutting wire out of things and seeing it countless times.

What's strange about that connector melting? Nothing, it is directly hooked to the resistor coil which is the hottest part there, they mount it in the rad shroud simply trying to cool it off. 50% of the ones you find in the junkyards are melted the same way, a common problem. Heat is a direct byproduct of a lot of resistance and normal, why heatsinks were created. The heat conducts backwards through the leads to the connection spades and then they melt also due to being too small, compare the size of the spades there to the ones further back up the circuit. Somebody messed up there in engineering. Those spades are too small and insubstantial for 10 gauge wire and the amp used there. The actual cross section at the connection is smaller than the wire gauge itself. Why most wiring fails usually at the connectors, a common engineering mistake. Made even worse by the extremely small tines which come out to grasp the spade on the other side..........practically no contact point there at all. Engineering best practice would be to make the connection BIGGER in cross-section than the wire gauge itself to ward that off. Again, look further back up the circuit for the connections at the shroud to harness, they are much closer to the correct size. And they NEVER melt.

The words 'wire melted under insulation' are perhaps a poor choice but essentially the same in effect, VERY common for the connection to look fine on the outside and pull it apart or even have to cut apart (two plastic moldings melted together) like I did on my two cars and then you see that inside everything is melted. The wire per se may not be but a worthless point as the connection is STILL flawed.

 

I wonder if we are talking about the same connector? I meant the one where all the wires to the fans and the resistor are connected to the harness. It's a big plug with 6 connectors in it. They are not spade type connectors. I have not inspected the connections on the resistor itself, since a measurement of resistance at that main plug showed a reasonable value for the resistance, and the fan works at low speed as expected when the low speed relay is shorted (contacts 3 & 5).

 

http://www.focusfanatics.com/forum/...rum/general-technical-chat/272143-car-running-without-coolant-fan-resistor.html

Post #2, the pic and part indicated in yellow. Commonly melts there.

All our connectors there picced are pairs. The others shown there are bigger.

 

Went back and checked, you are running 1.6 motor which we do not have here stateside.

 

Same problem, twice. Once at 100K, again at 180K. Zetec 2L. Well maintained. Blew two resistorsa and one Relay (low speed) during this go at troubleshooting. Fans and harnesses are original, with high voltage pull on start-up. POW!, there goes the resistor.
My buddy showed me how to bypass the resistor and ensure the fans run at 230 F. Jumper from low speed relay to high speed relay. All good. This only cost me $150.00 in parts (the Smoked resistore and LS Fan Relay...gotta hold the repair costs down when the cost more that the value of the ZX!). That's not counting the #10 jumper wire snip from my wire pile. Pics attached. Shooting for 300K on this scooter.