Electrical Fan Spins Intermittently

Discussion in '1994 - 1995 Specific Tech' started by JordanB21, Oct 4, 2012.

  1. When my fans did work this is what it would do (a/c was off though), I'm assuming it's not reacting immediately to the a/c but it is to the temperature when it gets hot enough.
    That part was a joke, but I mean, it's a great way to stop screwing with the CCRM, but of course i'll still test the two pins when I get home (at school)
    I understand what you mean, but when people go with an aftermarket trigger or switch what do you mean? Adding relays, a switch?:p

    such as using the current tapped lower intake ECT, and putting in a relay to trigger the fan to come on.
  2. Using the ECT to trigger a relay almost never worked on the A9* processors (Fox III's), and I'm all but sure it would not work on a Fox IV.

    It just implies getting an aftermarket fan switch (which look like the gauge's sending unit, but they ground at a given temp, like 195*F) or using an aftermarket controller (like the 20 dollar adjustables at the parts store). Basically you're using an aftermarket switch to trigger the fan relay (since something in your stock triggering circuit is not energizing the fan relay).

    With either, you still need relay(s) to drive the fan, so one can use the stock relays in the CCRM or supply their own relays.

    The best option is to use a fully PWM controller but that'll be expensive. If you use a full PWM controller, you do not use anything from the stock wiring. On the plus side, since it's stand-alone, it does not mess with any of the stock wiring, so that stuff will remain in its current state (no cuts, splices, etc). Nice if you're desiring the ability to have a 100% OEM look again at some point.
  3. The goal of the car is to stay daily driver, I love the body style much more than my fox, but it's more fuel efficient and I'm on the fence of which car to keep in a few years (I'd pick this one hands down, but it's trouble and has some frame damage, not from me). Course, in the future, I hope to own another or different sn95, one I'm willing to modify for performance, and build that dream car idea I made about a year ago...so many roush parts in mind ;)

    I see what you mean, I'd probably prefer the PWN controller since it would leave the factory harness intact then. But that's why I would like to 'simply' (yeah, right, simply) repair what is there rather than add more.

    In with the results!
    Unplugged the ECT sensor (passenger side one) and nothing, the fan did not move, but the computer recognized it and the check engine light came on.
    I then back probed number 14 for volts at temperature (brought it upto A no the NORMAL scale, typically where it would come on).
    While it was off it read in .50 or so mV. When it clicked on it read a continuous .28 to .29 Volts at pin 14 at temperature.

    I grounded pin 17. Nothing occurred.
    The method was by taking the needle tip of my multimeter (they unplug from the probes) and then connecting a jumper to the back of the probe and sticking it into pin 17 from behind and the other end to the negative terminal on the battery as a ground.

    I would say this points to the CCRM again, but I do not know the proper voltage it should be receiving to click on the relay at pin 14. So that leaves it back to is it getting enough voltage, and again, if the relays are clicking on.

    Side note: I only say stuff that seems obvious like my last little paragraph because they're my interpretations of it since my knowledge is all guess knowledge and I put it up there to be corrected or not. :p
  4. One bonus with a PWM controller would be that you could put it in your fox down the road if you get rid of the SN.

    When you tested pin 14 and 17, the ECT was connected, right? Pin 14 should show 12V. If low functioned properly at 208*F, that wire should have shown near 12V. An SPST relay generally requires 250-500 mA to energize the coil, so a reading of .28V would have been super marginal. Did you ever apply 12V to Pin 14? Did low speed come right on?

    This is weird. Going back to the test pathway, check the inputs and outputs for high speed (HEDF). See the fan testing portion below:


    To recap, the easiest way to get an idea of where the issue lies is to actually ground Pin 17 and (separetely, in another test) supply 12V to Pin 14. If both speeds function fine when you do each test, the CCRM is likely fine and the issue is likely from the EEC. In your case, Pin 17 does not seem to make high speed energize. Testing the in/outs (pins 6, 7, 13, 3, 4).

    If both of the above tests fail, the issue is likely the CCRM or the inputs or outputs at the CCRM (if the fan itself bench-tested fine). Please recap the Pin 14 test (supplying it with 12V). I know it's in there but this is long and a recap is always good (I scan and misread all the time). :)
  5. Yeah the ECT was connected. And I didn't try to apply 12v but I will here in a minute.

    I could go back and try and ground pin 15 (the one related to the low speed fan coming on), as I only tried to ground pin 17.

    So i'll do both tests to pin 17 (with a/c on) and pin 14 by adding volts at temperature.
    along with testing the ins and outs since I seem to be doing better with back probing.

    so back to outside! (running out of daylight, maybe an hour or so left:O)
  6. This is being typed as each is tested.
    Pins 6, 7, 3, 4 all show good voltage.
    Pin 17 grounded shows no change (while max a/c is on).
    Pin 15 grounded does nothing (this first tested when the low speed fan shouldn't be on as a measurement).
    Pin 14 shows .57volts at a high from poking through insulation when fan should be on.
    Pin 15 grounded does nothing while the fan should be on.
    Pin 14 grounded does nothing while the fan should be on.
    Pins 1 and 2 both show 12 volts.

    I basiclly collected all this data, and can't interpret. it -___-
  7. Since 6 and 7 show 12V, there should be power to the fan at that time. Is there 12V at the high speed wire at the fan connector?
  8. The middle prong (unplugged from the fan) reads .45ish (never more than a volt) volts.
  9. Uhm. Well here's the weird thing. I tested it unplugged a second time, when I pressed it inbetween the plastic and metal on one side it got that less than one volt reading. I then tested between the metal and plastic on the lower side (side facing closes to the fan) and it tested for around high 9 volts to low 10 volts.soooo.

    Maybe omit that data, and count it as a random error, but it seemed constant.

    And just tried to supply 12volts to pin 14 to kick on the low speed fan with the high a/c off and nothing happened. I tried both by back probing and poking through the insulation, neither yielded results.
  10. I'm not entirely sure I follow you. You can just unplug the fan connector and see if you have 12V when your leads are biased across both outside terminals (the fan connector is labeled. High and ground are on the outsides). Your voltage reading should be the same as that of 6 or 7.
  11. I'll go check again, the middle prong was the only one to show voltage, the outter right one read OD, I assume to be the ground, and the outter left one (I know the lefts and rights make no difference to you since you're not looking at it:p) read in mV.

    Be back in, like. 4 minutes or so.
  12. Ignore what I said, bad readings, probably my fault.:p

    New, accurate, triple checked, readings are

    the high speed prong with max a/c on reads 11.68 constant volts. the middle prong read .59 volts and the ground read mV*

    *all readings were taken at the same time with the max a/c on.
    what I said about the middle prong stayed true, I just got a bad reading from the highspeed prong the first time I checked.

    and all testing was done by unplugging the fan connector, I guess I just described it weird.
    The fan also doesn't move in a hard to push way, it has some resistance, and to reiterate I did run jumpers to it on two different occasions and it spun both times.
  13. Ensure the fan connector ground shows less than 5 Ohms of resistance to battery ground.
    The fan motor should have little resistance freewheeling, even during breakaway.
  14. It read anywhere from .29 kilo ohms to .9 kilo ohms depending on if I touched the negative battery terminal or just the ground connected to the negative battery terminal.
  15. So the ground is ok and 12V is leaving the CCRM towards the high speed fan, but the high speed fan does not come on. Is there a circuit breaker installed inline on the power wire or are the fan terminals burned?
  16. Yeah, the little "fix" that Ford did with the recall deal. Any SN95's I've bought with those on them I immediately chuck them into the trash! They only serve to overheat your engine.
  17. There's never been any type of circuit breaker to my knowledge or visible in the line thats been installed.
    and the piece that plugs into the fan, the prongs all look fine, minor blackening, but not burns of any kind or melting.

    Where would those breakers be? I could look for it, but I'm pretty sure we never brought it to the dealer for any work. Though we've only had it since 2000 and I was a youngin' for the the majority of the ownership.

    Edit: This morning I looked the lines over for any type of breaker from the fan to the ccrm and from the ccrm to where it splits into the main harness there isn't anything but wires.
    So unless they breaker was put elsewhere, there isn't one.

    ...though. I could always goto the dealership and have one put in and them come back and say it caused the fan to not spin:p oh if only it were that simple.
  18. The breaker is next to the fan motor. If it was there, you'd see it.
  19. Then it isn't there. But, of course, I'll look again in the morning.

    Edit: looked a bit ago. Compared with online images, that thing is big and ugly,but no it is not there for sure.

    Moving on for now (if there's anything left) any other trouble shooting to go through? I feel like we're or I'm running out of possibilities and options.

    And refering to this (where you, as luck would have it, posted) http://www.stangnet.com/mustang-forums/threads/fan-catching-on-fire.787066/
    My fan doesn't spin as described. If I were to flick it with my finger it wouldn't rotate freely for a full rotation or near. It would rotate for probably about 20 degrees give or take. It has resistance but isn't stuck.
  20. Sounds like an issue to me (time to replace or renew the fan motor).

    Are we still not sure why you don't see the same voltage at the HEDF output at the CCRM and the fan's connector? Even if the fan motor was toast, unless there was a CB in between the two, they should show the same voltage.