engine dying due to electric fan

Discussion in 'Small Block Mopar Engine' started by oldmusclelover, Jan 12, 2018.

  1. oldmusclelover

    oldmusclelover FABO Gold Member FABO Gold Member

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    hello all, hoping to get some help here and couldn't find this in any search. have a 340 engine, electric fan (seems to be hooked up properly, but I'm not good with electrical). engine runs perfect, until the fan kicks in, then it seems to be robbed, and dies. the only thing that makes me wonder is, that it's hooked into the ignition switch (which seems to be proper?). any help is much appreciated. thanks in advance. believe it's a vintage air thermostat with wiring kit. again, thanks.
     
  2. RustyRatRod

    RustyRatRod Just another dumbass. FABO Gold Member Technical Editor

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    You cannot connect anything to the ignition circuit. It's for the ignition. The fan is a high amp draw. Your connection is anything but "proper".

    You should run the fan from a dedicated switch, through a relay, possibly through a thermostatic switch if you want and to the fan.
     
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    • oldmusclelover

      oldmusclelover FABO Gold Member FABO Gold Member

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      that was my first thought, but then checked some wiring videos and found they sourced the power (not the main, my fault for not mentioning this, the main power is from the battery) from the ignition (the switch, if I understand the wiring). I have the original diagram for wiring and it the blue wire (off 85 on relay) to be hooked to a '+12 volt power source'. should I move it? and would it be alright to put it back to the battery? have the 4 prong system.
       
    • oldmusclelover

      oldmusclelover FABO Gold Member FABO Gold Member

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      oh, and thanks for your help RustyRatRod, most appreciated.
       
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      • brian6pac

        brian6pac Well-Known Member

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        I would go right from the battery to the relay to the fan, and make sure you have a big enough wire 12ga 10ga depending on how long a run it is.
         
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        • RustyRatRod

          RustyRatRod Just another dumbass. FABO Gold Member Technical Editor

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          What I am going to do to all my future projects is mount a power and ground buss somewhere under the hood. That way I can easily wire new high amp circuits in if need be.
           
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          • oldmusclelover

            oldmusclelover FABO Gold Member FABO Gold Member

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            that wire is sufficient, I believe. red is to circuit breaker, then to 30 on relay. purple is to fan, off 87. white is to thermostat, then ground, off 86. it's the blue wire that boggles me, off 85, it only states "+12 volt power source", and at this time, it's hooked to the back side of the ignition switch, on the run side, not accessory. again, thanks for the help Brian, does that help?
             
          • oldmusclelover

            oldmusclelover FABO Gold Member FABO Gold Member

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            great idea, but this was in the vehicle, so I'm just trying to get it running with a little help from you folks. thanks for all the help, it really is appreciated.
             
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            • crackedback

              crackedback FABO Gold Member FABO Gold Member

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              86 is usually a trigger
              85 is usually a ground
              Some relays are finicky with which terminals are excite power and ground terminals. Some it doesn't matter.

              30 and 87 are your heavy power carrying blades.

              If you only want the fan to run with key on when engine gets hot using the thermostat to ground circuit you are fine. You don't even need to keep the power switched as it shouldn't turn fan on unless thermostat triggers it by grounding. I still usually put those on a switch just in case. That way when the car is off, you can have the fan running until it cools to thermostat point.
               
              Last edited: Jan 12, 2018
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              • oldmusclelover

                oldmusclelover FABO Gold Member FABO Gold Member

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                maybe I didn't give the right wiring, here's a diagram. I thought (from what I read and saw) that the 87 was just a low wire need? hope this diagram will help. thanks crackedback wiring diagram.jpg
                 
              • oldmusclelover

                oldmusclelover FABO Gold Member FABO Gold Member

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                whoops, I meant 85
                 
              • crackedback

                crackedback FABO Gold Member FABO Gold Member

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                Yeah that's OK.

                Be VERY careful on mopars and where you pull power from.

                I WOULD NOT be running factory charging system wiring with an electric fan. You are asking for a melted bulkhead and potential fire. Problem with fans is that they tend to run when the engine is on or off. If you are running the fan only with the engine on, battery is a bad spot with factory wiring.
                 
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                • oldmusclelover

                  oldmusclelover FABO Gold Member FABO Gold Member

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                  please, I'm open for suggestions. actually, the original post is for help. and yes, with the fan on the ignition switch, it only runs when the key is on. any help is appreciated, more than appreciated. what do you (or anyone else) suggest? can the second power wire be connected to the battery as well? or does it need another power source?
                   
                • crackedback

                  crackedback FABO Gold Member FABO Gold Member

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                  The only real concern is where the wire connected to the 30 terminal is attached.

                  The charging system wiring is marginal at best. What I would do is install something like this to make sure the alternator power is getting to the fan, bypassing most of the bulkhead and dash assembly. There is no perfect place to pull power on mopars in all key states. Have to improve what's there to make it tolerable. :)

                  [FOR SALE] - Charging System Bulkhead Wire Around

                  You are going to tax the bulkhead with the fan draw. That will create heat in a connection that was crappy from the beginning.

                  I've been doing fixes and making items that keep our mopars from burning up for a long time. Glad to help.
                   
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                  • oldmusclelover

                    oldmusclelover FABO Gold Member FABO Gold Member

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                    appreciate your help crackedback, but the problem with the system is....as soon as the fan starts, the engine will bog down and die. something seems to be stealing the power? any ideas?
                     
                  • crackedback

                    crackedback FABO Gold Member FABO Gold Member

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                    It's taxing the wiring, more amps = more heat, more heat = more resistance, more resistance = a BUNCH of voltage drop.

                    Stock period mopar alternators SUCK at idle as well. So if you are idling, fan turns on and saps whatever energy out of the system, there is not much else to keep up. If you have a voltmeter, watch it when the fan turns on. A lot of engine electronics will not function at low voltages. Voltage drops below the point that a igniotn box must see, done- shut off.
                     
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                    • RustyRatRod

                      RustyRatRod Just another dumbass. FABO Gold Member Technical Editor

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                      Just askin here, but do you HAVE to run an electric fan? The Mopar clutch fan is a great piece and requires nothing but a belt to operate. Just a thought.
                       
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                      • BigBlockMopar

                        BigBlockMopar BigBlockMember

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                        Measure voltage over the coil when the fan kicks in.
                        It's also mostlikely the added power-draw of the fan is taxing the alternator so that in turn will bog down the engine. When the rpms drops, so does the alt output and it's all downhill from there.

                        I've got a 360ci with a modern Nippo alternator on an engine teststand. When I flick on the relayed fan's switch it also bogs the engine down noticably in the beginning.
                        A 'slow-start' PWM fan-controller would help greatly as well as it doesn't shock the electric system so much.
                         
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                        • Tooljunkie

                          Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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                          Mentioned vintage air.
                          As in air conditioning?
                          Also,improve your engine to body ground. There may be insufficient grounds.
                           
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                          • WoodenNickle

                            WoodenNickle Just Damn.....

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                            I'm pretty sure the fan is blowing out the fire in the cylinders. Yeah. That's got to be it. Maybe you should have bought a less powerful fan.
                             
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                            • oldmusclelover

                              oldmusclelover FABO Gold Member FABO Gold Member

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                              I'll check later this morning, don't want to wake the neighbors too early on a Saturday morning.
                               
                            • oldmusclelover

                              oldmusclelover FABO Gold Member FABO Gold Member

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                              and a good thought, I like mechanical, and the radiator has been upgraded to a 3 row. but, looking to keep the electric if I can fix the electrical problem at this time. I don't like to rely on electrical components, but since I'm a gauge watcher, I don't think it will be a problem, hopefully (knocks on wood).
                               
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                              • oldmusclelover

                                oldmusclelover FABO Gold Member FABO Gold Member

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                              • oldmusclelover

                                oldmusclelover FABO Gold Member FABO Gold Member

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                                I will do as you suggest, a little later this morning. I really like the idea of the 'slow start', even an illiterate electrical imbecile like me can understand those 'layman' terms. thanks, much appreciated.
                                 
                              • oldmusclelover

                                oldmusclelover FABO Gold Member FABO Gold Member

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                                no, that was the supplier of the wiring. going through paper work to get better info, believe the fan is a LoBoy by flexalite. I'm hoping my engine/body ground is sufficient, it's 2/0 welding cable. thanks, all input helps, and the easiest fixes are usually overlooked. as Carl said