# ZAPCO ST-1 in Protect Mode when Hot Outside



## BayouGuy (Jul 15, 2015)

I'm hoping someone can help me diagnose this problem so I don't have to send amp off for repair. Any thoughts would be appreciated.

I have an ST-1 driving an 8" JL sub and two ST-4X's driving the main speakers in my truck.

The ST-1 and the ST-4X's are all powered from a single distribution block (0-gauge/block/4-gauge) and grounded separately(4-gauge). All three get REM 12v power from an Audison BitOne.

I installed all of them in a new truck in February, when temperatures were moderate here in Louisiana. The amps worked fine until June, when temps started climbing above 80F.

The STX-4's continue to work fine. The ST-1, however, goes into protect mode if the temperature inside the truck is 85F or above WHEN I START IT. In the morning, when ambient temperature is ~75F, the amp starts up fine and continues to work as long as the truck is on. Even if I listen to something heavy on bass (i.e., when you would expect the amp to heat up some), it works fine--as long as it was cool when it started up. Any time the temp inside the truck is 85F or above when I start it, the amp goes into protect mode immediately. 

If the truck was hot when I started it (and amp went into protect), if I drive around long enough for the A/C to cool down the cabin, the amp will work if I turn the truck off then on again. Again--seems like as long as the cabin temp is below 85F at startup, the amp works fine. 

I have not noticed any exceptions to these rules, except one: Regardless of how hot the cabin temp is at startup, if I only turn the key part of the way ("ACC"), but don't start the engine, the amp will work. But if I start the engine, it will go into protect. My truck is a 2015 Tundra, and when you turn the key from ACC to ON, it resets all electronics. When I realized this, I tested the REM power with a voltmeter. In ACC mode, the REM power is ~12V. With engine running, REM power is ~13.4. _ [These voltages are from memory. I will re-check them tonight and correct them if wrong.]_ Remember, the REM lead from the BitOne is daisy-chained--all three amps see the same voltage.

One other thing worth mentioning... The REM leads from the Audison BitOne are delayed about 6 seconds (i.e., when key is turned, BitOne powers up, waits a few seconds, then turns on REM leads to amps).

If anyone has any ideas, please let me know. Thanks very much.


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