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Thread: How hard is recapping?

  1. #31

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    I think he means connect the fan directly to 12 volts. You can also wire an intermediary switch and switch it on when the temperature is going up. But unless it's real hot, the fans shouldn't be coming on, at least at highway speeds.

    He also said his a/c fan (blower?) wasn't coming on. First things to check are fuses and relay/s.

  2. #32
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    For any car I have to drive that's new enough to have an electric fan, electric fuel pump, relay driven ignition, or anything else critical for driving that's relay controlled, I keep a shunt relay in the glove box. It's just a spare relay that I've opened up and jammed a toothpick in so that it's always on. This can be a lifesaver.

    Really there's no need to turn off a radiator fan except to save a little energy. In situations where the fan control doesn't work, I prefer to just have it on all the time until I can do a proper repair.

    I couldn't tell you how many times I've had to use that shunt relay to turn on a fuel pump, ignition, fan, transmission, and I don't even remember what all else.

  3. #33
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    Quote Originally Posted by VERAULT View Post
    I just want to point out that even after an extensive overhaul on my cooling system. My 30 year old cars fans (both cooling and AC) arent coming on.... super.
    Use a volt meter or tone/light probe on both of the fan harnesses to make sure you have voltage going to the fans. The easiest to check first would be the A/C fan since it usually kicks on immediately or shortly after you engage the A/C system. The fan for the engine usually only turns on when the engine reaches operating temperature, or just after that.

    If you're getting voltage at the harness, the next thing would be to check the fans themselves. Since they have a habit of randomly kicking on (even if the car is off), disconnect the battery and attempt to spin both fans by hand. If you feel any resistance, grinding or any play in the bearings (either in/out or side to side) then you need new fans.

    If the fans feel OK, try taking a large flat screwdriver and hammer and give the fan motor housings a few good whacks. The reason for this is that most all radiator/condenser fans are brushed motors, even in modern cars. Over time as the carbon brushes wear down, the carbon dust and grime from the engine bay can cause the brushes to get stuck in their guides and the motor will start failing once there is enough of a gap between the commutator and the brushes.

    If none of this works, go up to the fuse box and start looking for blown fuses or bad relays. There should be a good diagram for your vehicle showing which relays and fuses belong to the fans.

    Quote Originally Posted by 2icebitn View Post
    But unless it's real hot, the fans shouldn't be coming on
    The engine cooling fan should always come on around the normal operating temperature of the engine, which is usually between 160-195F (depending on the thermostat used.) The radiator can't passively reject the enormous amount of heat a car engine generates, even when idle.

    Quote Originally Posted by 2icebitn View Post
    He also said his a/c fan (blower?) wasn't coming on. First things to check are fuses and relay/s.
    He was likely referencing the condenser fan. Many cars have a separate fan for the A/C condenser, which is usually smaller and has less blades on it. Most times the condenser fan is on the left side of the vehicle, while the engine fan is on the right side as viewed from the front of the car.

  4. #34
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    Quote Originally Posted by GiGaBiTe View Post
    The engine cooling fan should always come on around the normal operating temperature of the engine, which is usually between 160-195F (depending on the thermostat used.) The radiator can't passively reject the enormous amount of heat a car engine generates, even when idle.
    That is generally, but not universally true. Almost every car/truck I've owned will run just fine without a radiator fan as long as you don't idle at a stop for too long (under normal driving conditions). My wife once complained to me that her temperature gauge would go up when she waited at stop lights, "for about a year". She had a bad computer that would not turn the fan relay on. I installed an aftermarket temperature control. No point in spending $300 to replace the computer only to maybe have the same problem again in a few years.

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