Typical S197 overheating problem. But... Need advice on work around.

Discussion in '2005+ Mustang GT 4.6L Tech' started by Chad123, Oct 3, 2019.

  1. Chad123

    Chad123 Junior Member

    Hello, all. New here and really never have started a thread anywhere, so please forgive my ignorance in the format of my issue.
    I have 07 gt mustang 4.6 3v. Last year I had the typical overheating issue where the fan resistor in the fan shroud was getting hot at the pigtail and scorching the inside connectors. I replaced the pigtail and all was good for about a year. This has recently happened again where I am sitting at a light and radiator starts spewing out fluid. the fan isn't coming on and all relays are good. I have tested them. High and low speed. The current draw from my fan when hooked to straight power is good and approx 22amps. The BEC (fuse relay box) has the power and ground side pins are also scorched this time around.
    So the issue isn't the fan drawing too much current as this is a 40amp circuit. My big question is I want a complete work around relay circuit to bypass the wiring and the faulty BEC issue of this design. I have already wired a new 40amp relay and 30 amp circuit breaker. However, my understanding was I wanted to remove the CHT sensor in the head and install a new one and hardwire a sending unit to the new installed relay and all new 10 gauge wiring.
    I want the fan to come on with the new sending unit at 195 and off at 185. I have done tons of research and looked over all the forums and I come to the conclusion that if I remove the CHT sensor this will cause irregular voltage to the PCM and cause issues across the entire system.
    I want to install a new sending unit to engage the fan and need to know the best place to install a new sending unit since there are no other pre tapped places on the 4.6. Keep in mind I have also ordered a new Water temp gauge and will need another place to install a secondary sending unit for my new gauge cluster. PICs are my actual photos of recent issues.

    I am aware of the other options for installing a sending unit in the upper radiator hose and or tap a 1/8 NPT into my water neck. I've heard doing this I will have a intermittent reading as the stat doesn't open and allow coolant threw until temp is at the 180 and opens the stat. However, if my stat opens at 180 when it needs to then my future install of a 185 sending unit on at 195 and off at 185 wouldn't this keep the engine in check due to coolant consistantly circulating and the fan pulling cool air thru when temp goes above the open stat temp?





    Last edited: Oct 3, 2019
  2. 07 Boss

    07 Boss Senior Member

    So what exactly is your question? If the fan comes on at 195 will it keep the engine cool?
  3. Juice

    Juice forum member

    I have a suspicion that making those mods will likely fix your fan issue but will create another one for you. Since your PCM controls the fan, and you plan on bypassing all that, you will end up with a check engine light due to removing the CHT sensor from the head.

    IMO, the reason those connections melted is due to the age of the car. Connections develop corrosion/resistance over time, that is the reason they melt. I found my connection at the relay pretty much in the same condition as your photo shows. This type of failure is pretty common on high current circuits as a vehicle ages. I would repair all that vs modifying.

    If you are dead set on separating the fan controls from the pcm, I would look into a thermostat switch with a probe that you push into the radiator fins or installs into the upper hose or something like that. Leave the sensors in the head so the PCM isn't affected. The PCM uses the CHT sensors for more than just fan control.
  4. DiMora

    DiMora More Is Better

    I agree with that 100%.
  5. RED09GT

    RED09GT Senior Member S197 Team Member

    Yeah, way too complex of a work-around. The system works well until parts reach the end of their service life. Replace it with new parts and call it maintenance.
  6. 01yellerCobra

    01yellerCobra forum member

    Can you use the original power wires to run a couple relays? Or even just one relay and have the fan at one speed. Pull the power directly from the battery. Less chance of future meltdowns I would think.
  7. 08MustangDude

    08MustangDude Resident Fuktard

    AS these fans get older, the motors draw more and more current due
    to resistance. That is caused by dirt, or the motor going bad. To truly
    repair it, replace the fan with a brand new one, then fix the wiring. It did
    not happen till now, much much later right, not when new? Well, there's
    a reason, the AGE of the fan motor.

    Start up of any motor has a higher current cost, as the fan motor ages and
    has drag or resistance, that start-up AMP cost goes up, thus more current to
    keep it running. For example, if the motor stalls, the current draw will
    spike, and stay high, then melt the wires.

    The motor becomes loaded with resistance due to dirt, lack of lubrication,
    rust, whatever. As the motor is loaded, the back emf reduces because of
    the momentary reduction of the speed, and the motor draws more current
    to produce the same amount of the back EMF to produce torque for additional
    load on the motor, and also to maintain the motor speed at increased torque.

    When nice and new and fresh, under no load condition, the motor runs at its rated
    RPM and, because the back EMF induced due to armature current is almost equal to
    the applied voltage and motor draws less armature current.
    Lime1Gt and jewc75 like this.
  8. jewc75

    jewc75 Cant Stop, Wont Stop

    Im with him^. Just because a motor works does not mean its working correctly.
  9. Pentalab

    Pentalab forum member

    It get's worse. Typ dc + ac motor's have a typ starting current of triple the running current.
    You can measure that with the 'peak' function of a fluke 87 DVM. That start up current typ last only 1 sec..... but is enough to compound any issues. I have an oem 190 deg T stat on my 2010 rad. Starts to open at 190F....and fully open at 200-205 F. Low speed fan comes on at 207F...... shuts off at 197 F. I can watch low speed fan cycle over and over while in idle, in driveway. High speed fan (resistor shorted) kicks in at aprx 213 F.

    On my SCT-X3, VMP unlocked all sorts of stuff..and the low speed fan threshold can be set over a wide range. Ditto with high speed threshold. In fact, they overlap.

    I had that resistor, fuse, relay all burn up on my 2010 2 yrs ago. Replaced / repaired it all. Oem fan still used..... current draw was same as a new one....so left it in.
  10. brasil

    brasil Junior Member

    Sorry for my question here ... but wouldn‘t it be better to install a mechanical Fan ?
    I for my self ... I don‘ t thrust those e - fans
  11. Pentalab

    Pentalab forum member

    RPM of mech fan increases / decreases with eng rpm. That's exactly what u don't want. E fans have been in use since aprx early 80's. With the car moving at say 25-30 mph, u don't need a fan.
    Mech fans gobble up a lot of hp.
  12. brasil

    brasil Junior Member

    What you say is correct so far . But I have no problems to give up some horses - when I can stay relaxed . Because the good old mechanical fan does not brake . E - Stuff is always full of gremlins
  13. 1950StangJump$

    1950StangJump$ forum member

    So . . . roll down windows in lieu of AC then? Cable driven speedo, carburetor, and no ABS?

    Just askin'
    RED09GT likes this.
  14. Norm Peterson

    Norm Peterson corner barstool sitter

    OP's problem was very specifically electrical in nature. The fan itself could be overdesigned to the point where it was as reliable as an anvil, and the connector would still be what caused the cooling system to be compromised.

    Technological changes still have to be done up right - physically, mechanically, electrically, thermally, etc. - if you actually want to call them improvements and not simply exercises in technology for its own sake. OP's connector and Pentalab's resistor, fuse, and relay didn't make the cut, at least not long term.

    Listing those other things is a specious argument that has a hint of techno-snobbishness about it.

    Last edited: Nov 8, 2019 at 7:55 AM
  15. 1950StangJump$

    1950StangJump$ forum member

    Come on, now, Norm. The idea that a mechanical fan is the answer is ludicrous. And, my "specious" way of expressing that was meant to be humorous.
  16. RED09GT

    RED09GT Senior Member S197 Team Member

    I think all of us who owned a fox body can attest that a mechanical fan can cause just as many problems as an electric and be equally difficult to diagnose. I went through a few fan clutches and they always seemed to die at the most inopportune time. At least with an electric, you can tell when it is not working-not so much with a failed fan clutch. I
    even tried going to a non-clutch fan at one point and that was a huge mistake, sub 10's for fuel economy and it made my car into a complete slug, not to mention the fan noise was something awful. I later switched to a mark VIII electric and a flex a lite variable speed controller and lived happily ever after.
    I suppose you could try and fit a water pump and clutch fan from a 2002-2010 explorer or truck, build your own shroud and kill off 20 or so hp and a couple MPG as well.
    Last edited: Nov 8, 2019 at 2:14 PM
  17. Norm Peterson

    Norm Peterson corner barstool sitter

    brasil may have had more than his share of electrical problems. Maybe not so silly to him.

    Maybe so. But people trot out the exact same argument - down to some of the exact same examples - to beat down on those who are not as enthusiastic about the newer technologies as they are. Kind of hard to tell the difference between joking and "you're so not with it".