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  • 1965 - 1973 Classic Mustangs -General/Talk-
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Electrical Modification Opinions?

  • Thread starter Thread starter horseballz
  • Start date Start date Aug 20, 2011

horseballz

10 Year Member
Sep 30, 2009
824
19
49
Las Vegas, NV
Aug 20, 2011
#1
  • Aug 20, 2011
  • #1
Hi Folks,
So here's the deal. Now that I have my A/C, in my 68 Coupe, up and running I find that the plug on the back of the ignition switch gets kinda warm, especially when fan is on high. This tells me that the overall draw through the switch is a bit excessive, this seems natural, especially when considering 40+ year old wires, etc. I have a sort of simple idea to reduce the stress on the old wiring without totally butchering it or replacing it and would like opinions and thoughts on my plan. First off, everything electrical works with no intermittent connections. My thought is to:
1>Cut the main fat wire that comes off the "A" terminal of the ignition switch that provides "key on" power to all accessories and signal lights, etc.
2>Use this feed from the switch to activate/trigger with the key on a relay (60 amp or more) powered direct from the positive battery cable at the solenoid.
3>Run the load side/terminal of the relay to a 4 or 6 circuit fuse block located under my dash
4>Use one circuit of the fuse block to feed the other side of the wire that I cut from the switch, basically putting the relay "in line" to supply the accessory circuit and taking the load off the original switch and wiring.
5>Use another circuit from the fuse block to power the heater/AC system.
6>Still have 2 or 4 fuse circuits for possible future items.

What do you all think? Any pitfalls I'm not seeing?
Thanks All,
Gene
 

JonK

Member
Jun 6, 2007
276
0
16
Nashville (Smyrna), TN
Aug 20, 2011
#2
  • Aug 20, 2011
  • #2
Relays can be a huge help on overloaded circuits, I plan to do something similar with an 'accessory' fuse panel in my trunk for all my stereo, defroster, heated seats, etc. and will use relays to handle the load of the heavier ones. I plan to use individual relays vs. one large 60A one as you mentioned. 30A handle headlights which are the biggest draw and if you run through one relay and it overheats/fails everything will go our vs. separated circuits with a couple of related systems on each relay I figure.

Here's some links I've saved on relays to help me figure out how I want to do it:
Parts Express - Automotive Relays
http://www.parts-express.com/pdf/500-001.pdf

Jon
 

horseballz

10 Year Member
Sep 30, 2009
824
19
49
Las Vegas, NV
Aug 20, 2011
#3
  • Aug 20, 2011
  • #3
JonK,
Thanks for the thoughts. Headlights are already on relays feeding a new harness to the lamps. My intention was to supply the whole accessory system through the main 60A relay but split the A/C & blower motor (pretty high draw) away from getting it's power through the ancient main accessory system and it's associated wiring. I may even use a bigger main relay, with appropriate wiring of course, to possibly facilitate an electric fan setup in the future.
Thanks,
Gene
 
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