Relay

[Andrew]

I have mounted a relay switch near the center of my firewall to turn on my fuel pump. Can anyone suggest an easy place to wire #85 pin on the relay (bosch type standard 30 amp relay pins #30, 85, 86, 87, & 87a) to activate the relay when the ignition switch is on???

 

[Meep-Meep]

You can use one of the pins on the ballast resistor.

 

[Andrew]

Is either side ok? I was messing around with ti last nite, and the wire from the bulkhead disconnect to the balast res was very hot as was the balast resistor. The balast res was too hot to touch and the wire was close and at the bulkhd discnnct, it showed some melting. This single approx 16 guage wire from the bulkhead disconnect was spliced into and split 3 ways. I'm at work now, but from what I remember it went to the balast reistor, the voltage regulator(chrome box w/ 2 wires plugged into the top center of the face) and the alternator, and it was also jumped to the orange mopar performance ignition box. Then the opposite side of the balast resistor fead the MSD blaster 2 coil and a brown wirefrom the same terminal went back to the bulkhead disconnect. I know I'm dumping a lot on you and if this sounds like a jumbled mess I would not be surprised, but you seem to know your S*&^ so if this makes any sense, Is this normal or is this wire overloaded?

Is it normal for the balast resistor to be that hot?

Is there a better way to wire this? I'm assuming the lite blue and white wire from the bulkhead disconnect is from the ignition lock??? seems like a pain in the *** to change, but I will do whatever needs to be done.

 

[Meep-Meep]

One side of the ballast comes from the IGN and the other side goes to the coil +. Since you are only turning on a relay, which takes very little current and will probably work with slightly less than 12V, you can use either terminal, but to be "correct" look for the terminal that comes from the IGN switch.

The ballast resistor will get hot. That's why it's a big porcelain thing and by design will dissipate some big wattage numbers. Any time you run current through a resistance that device (resistor) will act like a heater. An electric stove is a perfect example. As for the wire getting hot and the resistor being too hot to touch that may indicate too much current flowing through that circuit and I'd suspect the MSD coil is trying to suck the guts out of the primary side, or there is too much resistance in the wire itself due to poor connections, small gauge, etc.. The lower the resistance the less heat built up. You might check the voltage across the coil with the engine running and compare it to a factory system. Since the coil is switched on and off the voltage reading will be a "duty cycle" measurement and end up as something less than 12V - usually around 9V for points. A low resistance coil will pull the 12V primary circuit down to unacceptable voltage levels and eventually cause something to fail.

You can try to swap out to a stock coil and see what happens. Also cleaning up any connections, replacing with larger wire (at least OEM gauge) on the primary circuit will help too.

 

[Andrew]

thanks.