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  1. #1
    Just a bit of BOOST
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    86 svo colling problems

    installed new factory fan and same problem fan goes on then shuts off after temp goes up
    does anyone know the amp rate of original fan and what after market fan switch will work on it

  2. #2
    OVER-BOOST!! GAboySVO's Avatar
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    SVO's: 2 - 9Ls
    The problem may be in your fan relay that is under the driver side dash just above your left otherwise known as the TRW fan controller. If you turn on the AC, does your fan come on and stay on until you turn off the AC? If so, the controller or the connector is the issue. There are to relays on the PCB of the relay. One for the AC circuit and one for the temp circuit. I just recently troubleshot an issue with the fan not working and it turned out that the connector was damaged due to heat generated when the wire was pushed out of the connector. It takes a 7mm nut drive to remove the controller. Rock Auto has replacements.
    Mike S

    '86 SVO 9L Leather
    '86 SVO 9L Road Warrior
    '96 300ZXTT

  3. #3
    Just a bit of BOOST
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    thanks, but the fan controller is new so are the rest of the cooling sensors on the engine. the fan comes on when you turn key and stays on till it reaches normal temps then stops and the car will over heat so I'm thinking of using an after market relay and controller but I have to know amp rate on the original fan which I,m trying to keep

  4. #4
    OVER-BOOST!! gbeaird's Avatar
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    SVO's: '86 2R
    That sounds the opposite of the way it should work. You sure you have the wiring correct? Perhaps one of the sensors is for a gauge, and not a fan controller, or light?
    Gene Beaird,
    86 2R SVO, G Stock,
    Pearland, Texas

  5. #5
    OVER-BOOST!! GAboySVO's Avatar
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    Quote Originally Posted by RICHMACH1 View Post
    the fan comes on when you turn key and stays on till it reaches normal temps then stops and the car will over heat so
    This is completely opposite of how it should work. So there is something that is reversed. If you temperature sensor resistance works in the opposite direction than the stock unit, that would explain the issue. I know the our fuel sender works completely opposite from the 87 and up models. - 79-86 Mustang Fuel Level Sending Unit Ohm Readings are approximately 73 ohms empty and approximately 10 ohms full. - 1987-97 Mustang Fuel Level Sending Unit Ohm Readings are approximately 22 ohms empty and approximately 145 ohms full. So if your sending unit is similarly reversed, it would explain your situation. Measure the resistance across the sender cold and then hot and report back the values. Maybe Ted can tell us what the values should be.
    Mike S

    '86 SVO 9L Leather
    '86 SVO 9L Road Warrior
    '96 300ZXTT

  6. #6
    OVER-BOOST!! svono50's Avatar
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    SVO's: 86 1C
    Mike, thanx for the shout out!

    As it turns out, our cooling fans are controlled by a temperature activated 'switch' (i.e.- open or closed) and not a sender like what the EEC and our dash gauge are connected to. The EEC temp sensor is in the top side of the lower intake between injectors #2 & #3, the dash gauge temp sensor is in the driver's side of the engine block below the oil pressure sending unit and the cooling fan switch is located on the bottom of the lower intake facing the firewall, below the knock sensor (see pics below).

    Ford decided to just use an on/off switch sensor to activate the cooling fan. From the EVTM, the "cooling fan temperature switch" closes at 226 deg F (yes, that high) and kicks on the cooling fan through the relay under the dash. The Ford shop manual states the switch closes at 221 deg F and opens back up at 201 deg F, FWIW. The cooling fan temp switch simply grounds out the control circuit to pull in the relay. The relay can also be triggered via the A/C pressure switch.

    So with the ignition on, engine temp below 221 deg F and the A/C off, you should not have a running fan. If your fan is running as you described, you are somehow getting a grounding signal through the cooling fan temp switch or power signal from the A/C pressure switch. My first suspicion is the coolant fan temp switch is closed when 'cold' and opens up when 'warm' or 'hot'...completely opposite of what it should be. When the engine is 'cold' and running with the fan running, disconnect the cooling fan switch plug and see if the fan goes off. If it does go off, a quick continuity check across the switch terminals will confirm you have a faulty cooling fan temp switch. When 'cold' it should show an 'open' circuit (i.e.- no continuity or infinite resistance). You may need to pull the switch out of the intake, depending on how good you are getting some probes onto the switch's terminals.

    If the temp switch is working correctly, next step would be to disconnect the A/C pressure switch located on top of the accumulator on the passenger side of the firewall and start it up again. If the fan still runs when both the cooling fan temp switch and pressure switch are unplugged, then you have either a bad relay box or a wiring issue where something is shorting to ground and giving a false signal to the relay. Since your relay is new, that shouldn't...but doesn't guarantee...be the issue.

    My first hunch is a bad cooling fan temp switch, but you will have to let us know what you find. Good luck.

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    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

  7. #7
    Just a bit of BOOST
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    thanks guys I just got back to the car ,I aim in the middle of packing to move ,so I will try a few things suggested from ted and see what happens by the way every switch and sensor has been replaced

  8. #8
    OVER-BOOST!! svono50's Avatar
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    I had a 'bad' ECT sensor one time, so don't rule that possibility out. Also, make sure all your connections are fully seated. Good luck and let us know what you come up with.
    Ted
    86 SVO Mustang
    17 Cooper S Clubman ALL4

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