"Dart67"
Well-Known Member
I have been intermittent weird problems with my F.A.S.T. XFI/XIM electronic fuel injection and my new Coil Near Plug ignition system.
During the process of trouble shooting the tune by logging a number of parameters, my friend Norbs David noticed that the battery voltage was low.
This prompted me to trouble shoot the charge circuit to the battery in the trunk. Due to having the battery in the trunk, I have installed an NHRA Battery Kill Switch.
The trouble shooting showed that I had 14.7 volts at the alternator but only 11.4 volts at the battery. The battery is a brand new Optima Yellow top.
When I checked the alternator input to the kill switch, I had 14.6 volts. But, the output of kill switch only showed the 11.4 volts.
BAD Kill Switch. But why, what was wrong with it.
So I took it apart. What I found was two sets of double ended contacts for the two circuits. The primary circuit has a heavy steel bar that completes the circuit.
The secondary circuit is insulated from the primary circuit and mounted below it. The double ended contact on this circuit is a thin piece of Spring steel with a pin type contact mounted on each end.
When the switch lever is moved from Off to On both the contacts move as one and are Pushed up to make contact and complete the circuits.
The spring steel of the secondary circuit appears to have gotten hot from too much current load and lost its spring tension therefore not making contact.
I have purchased a Cole Hersee 75912-BX Dual Battery disconnect switch as a replacement.
This switch has Electrical ratings of 125A continuous and 750A intermittent for 15secs On and 5min Off.
This switch has two circuits, A input, A output and B input and B output.
For it to function as needed to kill the battery and alternator feed to the car, I had to connect one set of the A an d B terminals together on the battery side of the switch.
To make this connection, I made a heavy connector link from a piece of 1/4" thick Copper plate.
The alternator input will be on one A post and the supply to the starter and vehicle wiring will be on one of the B post.
This is the cable side of the Old Switch. If you look around the lower pin contact you can see where it got hot from too much current flow.
This is the "Inside" contacts of the old switch. If you look close on the lower brass contact you can see a burned arc spot.
This is the "lift mechanism that pushed the contact bars up to complete the circuits.
This is the cable side of the new switch.
This is my "Home-Brewed" 1/4" thick copper Connector/Jumper.
This shows where the cables will attach.
On and Off
During the process of trouble shooting the tune by logging a number of parameters, my friend Norbs David noticed that the battery voltage was low.
This prompted me to trouble shoot the charge circuit to the battery in the trunk. Due to having the battery in the trunk, I have installed an NHRA Battery Kill Switch.
The trouble shooting showed that I had 14.7 volts at the alternator but only 11.4 volts at the battery. The battery is a brand new Optima Yellow top.
When I checked the alternator input to the kill switch, I had 14.6 volts. But, the output of kill switch only showed the 11.4 volts.
BAD Kill Switch. But why, what was wrong with it.
So I took it apart. What I found was two sets of double ended contacts for the two circuits. The primary circuit has a heavy steel bar that completes the circuit.
The secondary circuit is insulated from the primary circuit and mounted below it. The double ended contact on this circuit is a thin piece of Spring steel with a pin type contact mounted on each end.
When the switch lever is moved from Off to On both the contacts move as one and are Pushed up to make contact and complete the circuits.
The spring steel of the secondary circuit appears to have gotten hot from too much current load and lost its spring tension therefore not making contact.
I have purchased a Cole Hersee 75912-BX Dual Battery disconnect switch as a replacement.
This switch has Electrical ratings of 125A continuous and 750A intermittent for 15secs On and 5min Off.
This switch has two circuits, A input, A output and B input and B output.
For it to function as needed to kill the battery and alternator feed to the car, I had to connect one set of the A an d B terminals together on the battery side of the switch.
To make this connection, I made a heavy connector link from a piece of 1/4" thick Copper plate.
The alternator input will be on one A post and the supply to the starter and vehicle wiring will be on one of the B post.
This is the cable side of the Old Switch. If you look around the lower pin contact you can see where it got hot from too much current flow.
This is the "Inside" contacts of the old switch. If you look close on the lower brass contact you can see a burned arc spot.
This is the "lift mechanism that pushed the contact bars up to complete the circuits.
This is the cable side of the new switch.
This is my "Home-Brewed" 1/4" thick copper Connector/Jumper.
This shows where the cables will attach.
On and Off
