Battery Disconnect Switches - what are you using?

M

mustanghammer

New member
Over the last several years I have seen allot of Battery Disconnect switches fail for KC area racers. Everyone of the failed units has been from Longarce - 4 post for battery and alternator. Several of us had them fail while we were on the track - the result is that the battery is drained. The switches were connected correctly and they all functioned properly when tested by tech. It seems like this problem has gotten worse of late....perhaps Longarce has a new supplier.

So what are you guys using? Have any of you used the Moroso Super Heavy Duty 4 pole switch?

Thanks
 
Can you explain the failure a little better? How does a failed disconnect switch end up with a drained battery during a race?
 
I get mine from NAPA. I've had the one on my Daytona for about 8 yrs with no problems. And they are cheaper.
 
Scott, there is a partial thread on the specmiata.com/ site about disconnect switch failure. IIRC Dave Wheeler of Advanced Autosports stated that he has seen many failures with 4 post switches that have plastic included. As one would expect he claims he has never had or heard of a failure with the two post he sells.
 
Whatever you use, have a spare with you at all times. I've seen all of the most common types fail at one point or another.

K
 
I had mine fail this past weekend but when it failed it resulted in NO power to the car at all. If it is failing because it is draining the battery while racing then that seems different. Maybe at some point it was hooked up wrong creating a possible surge to the alternator which has affected the resistor and or polarity of the alternator. I am not an electrical genius but this is kind of how it was explained to me when I did mine wrong years ago. When the car was running the alternator actually drew voltage from the battery instead of charging the battery. This resulted from turning off the kill switch while it was running creating what was explained as a "surge" that affected the resistor. (My alternator has a resistor built into it not separate as some other cars.) Not sure if this helps or not... could be just a bunch of BS that I got so I would purchase a new alternator. FYI that same kill switch with the new alternator and wired correctly has lasted for about 5 years on the outside of the car, through winters in the NE with the car stored outside until about 2 years ago. only issue I have is if I turn off the car and leave the kill switch on for 20 min it kills the battery and will not restart without a jump start. Never figured that out to this day!

Stephen
 
JoshS said:
Can you explain the failure a little better? How does a failed disconnect switch end up with a drained battery during a race?
Click to expand...

The failures that I most familar with have occured on 3 1st gen Mazda RX7's using OE alternators. These are internally regulated alternators

All of the failures that happened on the track had the same symptoms. In my case it was during a qualifying session, First the shift lite stopped working and then the tach stopped working. Performance was okay and all of the issues happened at the end of the session. Since both the tach and the shift light are in the same circuit on my car I assumed it was a wiring issue I created. Later when I went to restart the car it was dead.

We ran a series of tests once a recharged battery was installed. Checking the voltage at the switch our first diagnosis was that the alternator died because we could see only 12V and not the 13.5-14V we expected when the car was running. As we investigated further we determined that the alternator was indeed charging but that the alternator lugs on the disconnect were not working. We replaced the switch with a new one and everything has been fine since.

The battery side of the switches seem to working fine. The alternator circuit are where the failures are occuring. Yes, we now carry a spare but would like a better solution
 
Now we don't get the same heat exposure in hill climbs but this is what we use in our FB's:
SP01335_lg.jpg


I get them from http://www.rallylights.com/detail.aspx?ID=3235
 
We have had two longacre switches fail, they were both purchased during the same time period.

From the looks of both of the switches the failure was on the smaller of the 2 posts. In both cases.

But one car had little to NO electrical strain on the Alt, (no lights not a whole lot of anything running). The second car was a enduro car with tons of stuff running, normal lights with HIDS, plus 4 other PIAAs, Electric power steerings, and all of the factory gauges in the car.

I just stay away from using the smaller posts except for very low loads.
 
jimmyc said:
I just stay away from using the smaller posts except for very low loads.
Click to expand...
The smaller posts are ONLY intended for minimal loads, virtually zero amperage. The purpose of the small lugs is to connect to the alternator's field sense circuit, which is nothing but what is self-describes: a circuit for the alternator to know what the system voltage is so it can adjust output voltage accordingly. The field sense circuit does not draw any significant amperage (if any).

So if you're running loads through this smaller circuit, I suspect you're overloading its capabilities and shorting or breaking the circuit.

GA
 
Greg Amy said:
The smaller posts are ONLY intended for minimal loads, virtually zero amperage. The purpose of the small lugs is to connect to the alternator's field sense circuit, which is nothing but what is self-describes: a circuit for the alternator to know what the system voltage is so it can adjust output voltage accordingly. The field sense circuit does not draw any significant amperage (if any).

So if you're running loads through this smaller circuit, I suspect you're overloading its capabilities and shorting or breaking the circuit.

GA
Click to expand...

You are speaking to about the longacre one right?

Interesting, that is what we figured, but on many other cars we never had a problem, (4 others running for 3 years). But after those two incidences we switched everything over to just avoid using them.

And we never found any info on line to suggest what they were to be used for.
 
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