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Thread: Atomic fan control

  1. #1

    Default Atomic fan control

    Howdy,



    Installing an Atomic EFI TBI and running into an issue regarding the fan control. Everything is new and the truck has never been fired yet. It has AC. I have the orange wire to the AC compressor and am only using the tan wire for fan activation. In my understanding the tan wire is just a ground and when wiring the fan relay the tan wire is to the relay activation ground, similar to a horn relay for wiring. Provide the ground and the circuit activates. I've checked and traced the wiring and still have an issue when the battery is hooked up the fans turn on. Even with the key off. I checked the relay wiring and I have power to the battery feed and activation feed. And the fan works so that wire is fine. When I check the tan wire from the atomic wiring it is always grounded, key on or off. I checked the settings in the menu to see if there was a default for fan on but could not find one. Any suggestions? Thanks.

    Chris

  2. #2
    Join Date
    Mar 2016
    Location
    Egg Harbor Township NJ
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    1

    Default Atomic fan control

    shutyoudown wrote:

    Howdy,



    Installing an Atomic EFI TBI and running into an issue regarding the fan control. Everything is new and the truck has never been fired yet. It has AC. I have the orange wire to the AC compressor and am only using the tan wire for fan activation. In my understanding the tan wire is just a ground and when wiring the fan relay the tan wire is to the relay activation ground, similar to a horn relay for wiring. Provide the ground and the circuit activates. I've checked and traced the wiring and still have an issue when the battery is hooked up the fans turn on. Even with the key off. I checked the relay wiring and I have power to the battery feed and activation feed. And the fan works so that wire is fine. When I check the tan wire from the atomic wiring it is always grounded, key on or off. I checked the settings in the menu to see if there was a default for fan on but could not find one. Any suggestions? Thanks.



    Chris

    Hey Chris... I have a De Witts Dual Fan Rad In My 65 502 BB Vette and am only using the Fan #1 wire which I believe is TAN to Fire off both Fans. It is connected to Both Relay Ground wires which are tide together as their are two relays for each Fan.

    I found out that you have to set both fans indicated on the hand held to the on temp you want. If you set one for lets just say 200* and the other which is not in used like I did for 300* the first one at 200* would not come on. After setting both for 200* all worked good . The fans went of at 190*.

    Don't see how the Atomic could be turning the fans on unless you have them set close to ambient temp. The Atomic does as you say provide a ground to fire off your fan relay. But I don't think it should show ground or Zero Ohms when measured to ground.

    Is it possible that the ground wire to the relay is seeing ground some where else? Maybe a check of that wire with the Ohm meter to engine ground will indicate something.

    I see you posted you did a check without the MSD hooked up and it worked ok meaning to me when you grounded the fan relay wire the fans ran...and when the ground was lifted ..the fans stopped.



    That would negate my testing the ground wire from the fan.

    I guess the next step is MSD Tech Line. Maybe something wrong with the ECU.

    Good Luck. Mark

  3. #3

    Default Atomic fan control

    I am using the Atomic to control 2 fans set at 2 different temps and it works just fine. The tan wire is set at 180* and the pink at 185*. When the preset temps are reached each wire will provide a ground to one side of the solenoid for the fan relay, the other connection for the solenoid goes to a 12v pwr source. On the contact side of the relay the + side to the fan is connected to one lead and +12v is tied to the other side of the relay contacts.



    When the engine temp reaches 180* the tan wire will provide a ground to the solenoid and since the other lead is connected to 12V the coil is energized and the contacts close. The contacts closing provides 12 v from the battery to the fan and its energized since the other lead from the fan is grounded to the cars frame somewhere.



    The pink circuit works the same way and is only used if you have 2 fans. If you want them to come on at the same time just set the same temps for both fans in the Atomic dash. I don't recommend using 1 relay to control 2 fans as the fans pulls a lot of amps.



    Here is a diagram that MSD provided in another thread on this subject,



    http://www.msdperformance.com/upload...%20fans(3).jpg


  4. #4

    Default Atomic fan control

    in the settings one fan is 190 and one is 188. Can't remember which is which but it shouldn't matter. When checking with an ohm meter it show conductivity between the tan wire and battery negative post. Something is up with that wire. I am going to trace it and see if something got pinched and it's grounding between the relay and control box. That's all that I can think of besides an issue with the control box. This is the last thing before firing it up this weekend and I'm trying to sort out all this stuff before its up and running. Hmmmmmmm.

  5. #5

    Default Atomic fan control

    The Tan wire should provide ground when Fan 1 reaches the set temperature. It will also provide ground when the AC kick-up wire is activated.

    A test light may be used, one end to 12V the other to the Tan Fan Control wire. Turn on the AC and see if the light turns on.

  6. #6

    Default Atomic fan control

    MSD Atomic EFI Support wrote:

    The Tan wire should provide ground when Fan 1 reaches the set temperature. It will also provide ground when the AC kick-up wire is activated.

    A test light may be used, one end to 12V the other to the Tan Fan Control wire. Turn on the AC and see if the light turns on.

    MSD Tech, So when the AC is turned on one fan will automatically come on if using a dual fan setup even if the engine is cold? Just curious.

  7. #7

    Default Atomic fan control

    bojo wrote:

    MSD Atomic EFI Support wrote:

    The Tan wire should provide ground when Fan 1 reaches the set temperature. It will also provide ground when the AC kick-up wire is activated.

    A test light may be used, one end to 12V the other to the Tan Fan Control wire. Turn on the AC and see if the light turns on.

    MSD Tech, So when the AC is turned on one fan will automatically come on if using a dual fan setup even if the engine is cold? Just curious.




    I'm not the MSD Tech but, that is correct. Whether the engine is hot or cold, the Atomic will start one fan when the A/C circuit is energized in order to provide air flow through the condenser. If your car activates the A/C when the defroster is turned on, it will start the fan then as well.

  8. #8

    Default Atomic fan control

    Yes, Fan 1 will come on when the AC is on (12V applied to the Orange wire), regardless of engine temp.

  9. #9

    Default Atomic fan control

    Thx for the responses guys, I didn't know that. I am getting ready to get the AC going so this is good to know. Thx

  10. #10

    Default Atomic fan control

    Follow-up.....

    Well everything was working. Now it is not. Just got the AC charged and started to use it. The fan would not turn on when the AC was on. I started testing wiring and verified that the Atomic system is receiving a signal that the AC is on. I then went into the Atomic gauges and watched for the fan to cycle between on and off when the AC clutch was engaged and not. This all was ok. I had also noticed the other day that the fans did not seem to come on at all. Then later they did. Never overheated but was a short drive. I then checked the wiring to the fans and relay. I verified that the fan ground wire for fan #1 was fine with an ohmmeter. Next step was to bypass the ground from the Atomic to see if the fans and relay were ok. The fans came on just fine. So with all this checking the only thing I can narrow it down to is the Atomic controller is not grounding the fan wire even though it thinks it is. I am hoping an MSD tech reads this so and maybe have an idea if the internals could be messed up. Anybody else have any other ideas?

    Thanks.

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