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I know service trucks use the frame for a ground and there is always something malfunctioning and it is 90% of the time ground related. So I am not going to criticize anyone for running grounds on a race car. Just their reasoning. LOL

Leon

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Big trucks the frame is rivided together which under
stress/load and time come loose creating a bad ground
joint so yes thats not good

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Don't forget all the fiberglass/aluminum cab, fenders, bunks, etc. I imagine that is more of the problem than the riVited frame.

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I know service trucks use the frame for a ground and there is always something malfunctioning and it is 90% of the time ground related. So I am not going to criticize anyone for running grounds on a race car. Just their reasoning. LOL

Leon

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Big trucks the frame is rivided together which under
stress/load and time come loose creating a bad ground
joint so yes thats not good

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Don't forget all the fiberglass/aluminum cab, fenders, bunks, etc. I imagine that is more of the problem than the riVited frame.

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Well you know damn well they dont ground to the fiberglass
and they dont like the alum either... specially that
the body is basically floating on the chassis...
they do have jumper grounds going to the chassis

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I thought the secondary contacts were used to brake the field circuit?

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I know service trucks use the frame for a ground and there is always something malfunctioning and it is 90% of the time ground related. So I am not going to criticize anyone for running grounds on a race car. Just their reasoning. LOL

Leon

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Big trucks the frame is rivided together which under
stress/load and time come loose creating a bad ground
joint so yes thats not good

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My Ford F550 bucket truck has a lot of electrical gremlins with the lights in the utility body. The guy who designs and wires at the upfitter is really up on his game. Old communications guy for GE. But, he uses the same junk relays these high dollar wiring systems do. AND WHEN THEY FAIL WE ARE STUCK 40 FT IN THE AIR. When are people going to understand most of these bosch style relays are junk. The best ones are in junk yard on factory fuse panels. I saw one wiring setup that I thought was the bomb until I noticed the 10 AMP relays. We have want a bee electrical engineers making these systems and selling them. They look cool and neat but, are full of gremlins. TIME WILL SHOW THIS. ARC stuff is pretty cheap and nothing trick about it and all the 14 gauge wire but it has lasted about 15 years in my car. Everybody was on the Painless bandwagon, just watch a mud truck shake all the fuses out in the floor and quit in the middle of a hole. I am despirately looking for something nice to replace this outdated ugly stuff. But, until I find something that I feel will last I will keep what I have.

When you build a car and it is still 400 lbs over weight for the class you limit weight by running grounds to the chassis. I later ran a bus system from the battery to the block and electronics. It has made no difference whatsoever. But, I know how to properly bond something. OH lets use easy terms ground something.

Leon

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You might consider the Longacre 45782. Secondary contacts rated at 125A.

Scott

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You might consider the Longacre 45782. Secondary contacts rated at 125A.

Scott

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I did look at that. I'm going to run a solenoid at the alternator output and use my 2.0 feed from the battery to charge. If that has voltage drop I'm in trouble.
Doug

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I know it has been done this way and some people get away with it but there is a potential drawback. The alternator is a HIGHLY inductive circuit and if you just disconnect the output with a solenoid or any other means you can get potentially VERY high voltage spikes. This is also a potential problem with just about any other method that doesn't connect the alternator output to the battery side of the master kill switch. Even the field circuit can generate spikes if there isn't enough electrical load on the same circuit. In the OE configuration the alternator output is always connected to the battery and the field circuit shares a power feed with the ignition and some other loads. Also, the electronic regulators may provide a 'soft-landing' for the field current when the power is turned off.

On my track car I have a field circuit switch in reach of the drivers seat and I turn it off if a tech inspector wants to test my kill switch. The kill switch will work either way but this way the alternator doesn't need to find an alternate circuit for all that stored energy in the magnetic field.

Way back when I killed my memory tach with voltage spikes. The only items on the circuit were the alternator field power, voltage regulator, tachometer and some tiny gauge lights. The gauge lights would flash brightly if I killed the engine with the second master switch I have near the drivers seat. I've since redesigned the power feeds so there's more devices on the alternator field opwer and regulator circuit and I never kill the engine with either master switch, always using the ignition switch that shuts off the MSD box.

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You might consider the Longacre 45782. Secondary contacts rated at 125A.

Scott

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I did look at that. I'm going to run a solenoid at the alternator output and use my 2.0 feed from the battery to charge. If that has voltage drop I'm in trouble.
Doug

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I know it has been done this way and some people get away with it but there is a potential drawback. The alternator is a HIGHLY inductive circuit and if you just disconnect the output with a solenoid or any other means you can get potentially VERY high voltage spikes. This is also a potential problem with just about any other method that doesn't connect the alternator output to the battery side of the master kill switch. Even the field circuit can generate spikes if there isn't enough electrical load on the same circuit. In the OE configuration the alternator output is always connected to the battery and the field circuit shares a power feed with the ignition and some other loads. Also, the electronic regulators may provide a 'soft-landing' for the field current when the power is turned off.

On my track car I have a field circuit switch in reach of the drivers seat and I turn it off if a tech inspector wants to test my kill switch. The kill switch will work either way but this way the alternator doesn't need to find an alternate circuit for all that stored energy in the magnetic field.

Way back when I killed my memory tach with voltage spikes. The only items on the circuit were the alternator field power, voltage regulator, tachometer and some tiny gauge lights. The gauge lights would flash brightly if I killed the engine with the second master switch I have near the drivers seat. I've since redesigned the power feeds so there's more devices on the alternator field opwer and regulator circuit and I never kill the engine with either master switch, always using the ignition switch that shuts off the MSD box.

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It's too easy not to run a cable from the - side of the battery to a ground block and branch off of that...When a electical problem pops up I know it's not a bad/loose ground, I can see everyone of them and they are all labeled.

IMO electical gremlins are the hardest to chase down so I like to keep it easy.
Here's my finished panel. Fan and fuel pump relays are close to the source but still ground back to the battery.

http://i1180.photobucket.com/albums/x404/Adobedude43/Shifter1.jpg

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Beautiful work!