Carson Kaddatz

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Okay so I’ve searched and searched but no one seems to be having the same exact problems that I am and the best way to go about this is just to explain what happened. I was sitting in a drive through and all the sudden I hear a squealing noise that sounds like some sort of siren, I look behind me and figure it’s the car next in line. Then I hear and feel a pop, so I pull out of line so I’m not in everyone’s way and I kill it and pop the hood and everything looks fine. Then I get back in and continue to go get my food, then I start to see smoke billowing out of my hood and my gauge reads hot, I pull it into a parking spot and kill it as fast as I can. I get out and there’s a River of radiator fluid on the ground and it’s boiling over in the reservoir but there’s no engine light. So I get some friends to bring a trailer and tow me to the shop, so we start it up when we get back, seeing if it will overheat again. When it got to about half way on the temp gauge the fan kicks on and starts squealing incredibly loudly (siren noise I mentioned earlier) . So I turn it off and we take the fan out and inspect it, it’s cracked and you can tell where it was rubbing so we went to town and got a new one and put it in. So we try to turn it on to see if that fan works and it won’t even come on. Next thing we did was checked the fuses, relays, and wires, come to find out, where you plug the relay into the fuse box was burnt. So I went and pulled a fuse box off of an 05 V6, plugged it up and put the fuses in and it started. When it starts it automatically gives me a fuel warning saying there is no fuel in the tank, yet the actual fuel gauge says it’s about half full. Next thing is when I slowly revved it to get the engine hot enough to kick the fan on, once I got to 2k RPM it kinda gave out. Now the engine light as well as the wrench light are on. It’s a long story but I’m just trying to figure out what to do next. I’ll appreciate any help.
 

Iceman62

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Why did you switch the entire fuse box? Re-trace your steps from the point where you installed new fan...then move forward.

Also, nice 1st post (intro)...
 

Joe combs

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You replaced the whole fan assembly, or just the fan motor? There is a resistor on the cooling fan that is known for going bad also... its mounted on the fan shroud ...
 

Forty61

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If there’s lights on have you pulled the codes to see what the car says is happening? May be unrelated or a consequence of other things but it may point you somewhat in the right direction.
 

Terry Murphy

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Possible, Thermostat can actually affect the PCM, regarding high, low engine fan speeds as well as, when to start up, and cut off. When installing thermostats on 05-10 Stangs (most cars .) you must tune in the PCM to adjust these temps. Usually, Stangs are 192-95 therms. can be lowered from 180-160 degrees. I prefer 170 degrees by Reisch, Gates, or Dueschworks. Moshimotto has the 160 degree. The catch is tune in the auto fan. and or upgrade to the Shelby fan as well (has lower temp. adjustments). There is a recommended tune in degrees from SCT and Diablo tuners. Just something to remember when you buy a used stang.
Sometimes they may have the wrong stat or none all together.
 

DieHarder

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BLUF (Bottom line up front) - I'm going to assume you have a wiring problem vice everything below so that's where I would concentrate my efforts by tracing and performing continuity checks on those lines. The remainder below is just in case...

Like OldTexasDog recommend starting with the basics. Ensure thermostat and water pump are working. If you have a tuner (like an SCT) pull codes to see what they say. If not, see if you can borrow a reader to get the codes.

Sounds like the BEC out of the V6 may be introducing new problems. You might want to fix the burned connector in the old BEC and start the troubleshooting process again.

Reinspect the BEC to ensure no other issues with the connectors and chase/perform continuity checks on any suspect lines (burned/corrosion/etc); each of the low/hi speed relays throughout the fan circuit. From your description it sounds like your fan was failing and/or the grounds were creating high resistance (hence, melting the relay connectors). Check/clean Ground connections and perform continuity checks from ground points (see wiring diagrams) to battery negative especially as there was obviously a high current condition previously. If those continuity checks are not less than 1 ohm (should actually be like a tenth of an ohm) I would chase and clean all of the ground points in the circuit and redo them until they are even that means adding ground lines. If the problem however was high resistance in the old fan motor that may be resolved.

Now that you've replaced the fan you need to test what part/s of the circuit is working or not. If you have wiring diagrams manual see pg 33-1. If not, they're online: http://iihs.net/

There's are several ways to test the fans/fan-circuit. A good explanation of the circuit is here:

1) With the motor running activate the A/C and check if the fan is on or not. If it runs that tells you the fan works at least. If that doesn't turn the fan on (turn the motor off) disconnect the main connector to the fan and run a couple of jumpers for Ground and Low/High to the battery to test the fan. Looking into the fan connector (where it connects to the plastic fan shroud) there are 3 pins. A single one on the lower left and 2 on the right. The single one by itself is ground. The two on the right are for low/high. If you jumper it and it runs you know the fan is good at least.

2) If someone/dealer has the proper test equip/monitor they can command the low/hi speed outputs from the PCM to come on. If they do the circuits work.

3) If you don't have that piece of test equipment (usually a dealer only item) another way to test is to get yourself a 4-post relay tester (
) and plug it into the fuse box and plug the relay on top. Apply a ground to the low speed relay ground input (lower right pin); repeat for the hi speed relay; if the fan runs the relays and the majority of the wiring circuits are good. If you're unsure if a relay is working you can substitute the horn relay (as long as the horn works). Now, you need to determine whether the PCM is providing a ground out on pins (6,7 of C175; PCM) to (C11, A12 of C1035B; BEC) (See wiring diagrams manual see pg 33-1) when it reaches temp settings to run the low/hi speed relays.

4) If you have software (like Logworks or similar) you can monitor the PCM signals and determine when/if they activate.

5) If you have someone who writes tunes for you may want to ask them to create a fan-test tune that will turn on both low/hi fans at a ridiculously low temp (say 40 degs). If the fan runs (with the car running) the circuits are good. Test each relay for operation by pulling the other. Then reload the last good tune.

I've asked Lito (Manuel) where the temp information comes from for the PCM output. His response below:
Q1: How does the PCM get it's temperature information? Where does it come from?
Q2: Does the Cylinder Head temp sensor have anything to do with turning the fans on/off?

Lito:
OK, the ECT temp is inferred as there is no actual sensor for that (in a 3V).

The ECT temp (even inferred) is used for FAN activation points.

The only temp sensor is the CHT that is screwed into the passenger's side head.

Folks, if I'm missing anything major someone feel free to speak up.
 

DieHarder

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Correction in above. The ground to apply to the relay is the lower left/(ground output) pin. Sorry, my bad...
 

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