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  1. #1
    FEP Power Member Broncojunkie's Avatar
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    Default E-fan relay problem

    I'm having an issue with my e-fan. More specifically, the relay. With the car parked and idling, it will come up to temp and overheat because the fan doesn't kick on. I have it wired the same way I've wired a few others. A fan controller with screw-in sensor/switch (non-adjustable 185 on/175 off, or something like that), then through a standard Bosch-style 4-pin relay.

    As the temp starts to rise past 185, I can reach down and lightly tap the relay and it will immediately kick on. My first, second, and third thoughts were that the relays (cheapo parts store chinesium) were bad. I've replaced it multiple times and even bench tested them. They all seemed to work perfectly. The last one, I noticed was marked as a 14v. I found another labeled as a 12v in my stash. Tested it and then installed and it did the same thing.

    I thought possibly a ground wasn't making good connection, so I ran it straight to the battery (-). Problem persisted. I've back-probed the fan controller wiring, relay socket, etc and everything seems to be working ok. All wiring and connectors are tight.

    Am I overlooking something obvious here? Driving the car, the problem doesn't happen often (usually, a bump in the road will cause it to switch on). I've replaced the controller, multiple relays, and l rewired it a couple times. I did just order some good quality relays, but the pin layout is different, so it won't work with the relay socket connector. I can cut out the connector and just install blade connectors on individual wires. Just haven't been in town for a week. I'll be home in 3 days and plan on getting it figured out.
    79 Pace Car - 331, t5
    79 Pace Car- 302, 4 spd
    79 Cobra - working on 351w, t5
    82 Capri- working on 302, t5
    82gt - working on 408w, c4

  2. #2
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    qikgts's Avatar
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    Default

    Maybe one of the connectors in the relay socket isn't tight enough to make a solid/consistent connection. It sounds like that could be it as the light tap makes it work even though they all work when bench tested and the symptoms are the same with multiple relays.
    '85 GT

  3. #3
    FEP Power Member Broncojunkie's Avatar
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    Quote Originally Posted by qikgts View Post
    Maybe one of the connectors in the relay socket isn't tight enough to make a solid/consistent connection. It sounds like that could be it as the light tap makes it work even though they all work when bench tested and the symptoms are the same with multiple relays.
    You may very well be correct. I will try eliminating the socket connector and wire straight to the relay and see what happens. If that doesn't work, I'll transfer those wires over to one of my better quality relays.
    79 Pace Car - 331, t5
    79 Pace Car- 302, 4 spd
    79 Cobra - working on 351w, t5
    82 Capri- working on 302, t5
    82gt - working on 408w, c4

  4. #4

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    What kind of fan? What capacity relay?

    Sent from my SM-G960U using Tapatalk
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI, T-5
    '17 Ford Focus ST
    '14 Ford Fusion SE Manual

  5. #5
    FEP Power Member Broncojunkie's Avatar
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    It's a chevy hhr oem aftermarket single fan. 12v 40a relay.
    79 Pace Car - 331, t5
    79 Pace Car- 302, 4 spd
    79 Cobra - working on 351w, t5
    82 Capri- working on 302, t5
    82gt - working on 408w, c4

  6. #6
    FEP Power Member Broncojunkie's Avatar
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    Seems to pull good air and it cools everything down very quickly with the 3-row aluminum radiator.
    79 Pace Car - 331, t5
    79 Pace Car- 302, 4 spd
    79 Cobra - working on 351w, t5
    82 Capri- working on 302, t5
    82gt - working on 408w, c4

  7. #7

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    Your relay may just not be up to the task. OEM fans draw a lot of amps. Last relays I used were 75 amp before I switched to a variable speed controller.

    Sent from my SM-G960U using Tapatalk
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI, T-5
    '17 Ford Focus ST
    '14 Ford Fusion SE Manual

  8. #8
    FEP Power Member Broncojunkie's Avatar
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    Quote Originally Posted by ZephyrEFI View Post
    Your relay may just not be up to the task. OEM fans draw a lot of amps. Last relays I used were 75 amp before I switched to a variable speed controller.

    Sent from my SM-G960U using Tapatalk
    Would that keep it from kicking on? I guess I thought that a relay that was rated too low would just cause it to heat up... maybe melt it... like a fuse. The more I think about it, the 12v "trigger" signal must not be getting to the relay (or the ground is interrupted somewhere). But if you say an underrated relay could do it, I'm all ears. Iirc, the fan pulls a little over 30a on startup. I could be way off. It's been a couple yrs since I read up on fans.
    79 Pace Car - 331, t5
    79 Pace Car- 302, 4 spd
    79 Cobra - working on 351w, t5
    82 Capri- working on 302, t5
    82gt - working on 408w, c4

  9. #9

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    Sounds like you've done your homework. Thought it was worth asking since not everyone does. Ask me how I know.

    Also sounds like you've eliminated almost everything as a possibility except the fan itself. Worth considering, anyway. Good luck!
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI, T-5
    '17 Ford Focus ST
    '14 Ford Fusion SE Manual

  10. #10
    FEP Power Member Broncojunkie's Avatar
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    Weird thing is that I can just barely tap the relay and it clicks on every time this happens. I'll be eliminating the relay connector here in a couple days. Hopefully that fixes it. The fan itself is working great. If you put power to it, it runs like a champ.
    79 Pace Car - 331, t5
    79 Pace Car- 302, 4 spd
    79 Cobra - working on 351w, t5
    82 Capri- working on 302, t5
    82gt - working on 408w, c4

  11. #11
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    How do you have the temp switch wired? Does it provide power +12 volts or ground? I always provide ground with any kind of switch. I never run positive power through a switch.

    Run Battery voltage to one side of the relay coils terminal, and the other side of the relay coil to the temp switch. Then run the second wire from the temp switch to a good ground. If the temp switch is only a single pin hook up, then it has to be wired as a ground. If that's the case, make sure the engine block has a good ground or whatever the switch it mounted to is grounded well.

  12. #12
    FEP Power Member Broncojunkie's Avatar
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    I do have the ground wired though the temp switch, which is mounted in a threaded water port on the intake.
    79 Pace Car - 331, t5
    79 Pace Car- 302, 4 spd
    79 Cobra - working on 351w, t5
    82 Capri- working on 302, t5
    82gt - working on 408w, c4

  13. #13
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    Do a resistance check on the temp sensor when it is closed at the temp needed to turn on the fan. Just measure across the sensor when it closes. Sounds like you have a voltage drop that is not high enough to trigger the relay. You can also check the voltage to the relay when the temp sensor closes.

  14. #14
    FEP Power Member Broncojunkie's Avatar
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    Just an update for this. I did figure out the problem. The main battery ground wasn't very good, evidently. I started having other electrical issues and eventually figured it out. Turn signals worked intermittently and my coil started producing a weak spark. Fixed the ground connection and everything is good as new.
    79 Pace Car - 331, t5
    79 Pace Car- 302, 4 spd
    79 Cobra - working on 351w, t5
    82 Capri- working on 302, t5
    82gt - working on 408w, c4

  15. #15

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    Glad to hear it!
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI, T-5
    '17 Ford Focus ST
    '14 Ford Fusion SE Manual

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