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Why does my blower motor kill my sound system


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So I installed a sound system back in the fall and was having issues with the cars alternator trying to keep up with it, especially if the headlights were on along with the heater going. The heater being the main power killer. When I installed the sound system I only used the power and ground from the stock harness to power the head unit, from there the entire sound system is wired independently.

 

so I just put a 90 amp ka24 alternator on my a14. Bolted up fairly easily, really plug and play. I thought not having enough amperage was my issue but no, I play the music at decent listening volume, then I turn on the heater and hear my system drop in volume. 
 

anybody have any idea why this is happening?

 

car for reference is a 1980 210 with an a14

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Does the 'head unit' power any speakers? or is it only to tell the amp what to do?

 

What gauge power wire to amp (I assume you are using an amp?) and what gauge for the ground? You should use the largest you can afford to reduce voltage drops at high listening levels. The ground wire must be at least the same gauge as the power wire. Welding cable is good.

 

 

I had a 240sx KA amp on my 710 sedan. That thing worked so hard that if the battery was low at start up the belt would screech from the load. My 710 wagon has a 100 amp 2002 Altima alternator. The power wire on it was larger than the stock positive battery cable!!!!!

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The head unit currently powers the door speakers, but even the subs in the back which are powered by an amp drop in power just like the door speakers. Both the power and ground wire for the amp are 8 gauge wire

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Is assume the heater is drawing current from the same circuit as the head unit. As a test run power direct from the battery to the head unit and then turn in the heater.

 

issue could be bad connections on that circuit. Easy to test! 

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A fan motor would take up a lot of current, and small gauge wires can’t handle both with the same time even though the alternator it pushing the juice. 

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I run my head unit on the main power to the amp. Has it's own 60 amp fuse.

 

 

 

Perhaps put a meter across the battery. Engine off with a good battery 12.6v. Running about 14.3v. It should be able to keep 14.3v with only headlights and a fan. Going by a 720 fuse box for example (keep in mind this is fuse ratings NOT what they draw) 2 x 50 watt lights are 8 amps, high beams 16 amp and the fuse is 20, dash and tail lights another 10? amp, perhaps another >10 amp for engine controls and heater >15 (going by 720 fuses) that's less than 45 amp and it is an 80 amp output. Keep in mind the alternator does not put out 80 amps at idle and low speeds. 

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1 minute ago, datzenmike said:

I run my head unit on the main power to the amp. Has it's own 60 amp fuse.

 

 

 

Perhaps put a meter across the battery. Engine off with a good battery 12.6v. Running about 14.3v. It should be able to keep 14.3v with only headlights and a fan. Going by a 720 fuse box for example (keep in mins this is fuse ratings NOT what they draw) 2 x 50 watt lights are 8 amps, dash and tail lights another 10? amp, perhaps another >10 amp for engine controls and heater >15 (going by 720 fuses) that's less than 45 amp and it is an 80 amp output. Keep in mind the alternator does not put out 80 amps at idle and low speeds. 

At idle I’m running 14.5 volts, with the car off it’s 13ish. I’ve got a deep cycle optima yellow top since the car tends to sit for long periods of time. The odd part is I don’t experience this issue as bad at idle as I do when I’m driving around. 

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Well what's the reading with blower on at idle and driving around.  If volume drops I'm expecting a voltage drop. Find out under what conditions maybe it can be fixed.

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4 minutes ago, datzenmike said:

Well what's the reading with blower on at idle and driving around.  If volume drops I'm expecting a voltage drop. Find out under what conditions maybe it can be fixed.

with the blower on, headlights running and stereo going im still at 14.5 at idle. I unfortunately don’t have a volt gauge installed so it’s hard to say when it’s driving around. But I kicked the engine up to 2.5k rpms while parked and the voltage barely moved
 

I was just taking a quick look at the wiring diagram and I think I figured out my problem. Off of the stock radio plug im running both the ground and the power for the stereo. Then I’m running the accessory wire straight to the battery. I’m thinking if I swap the power for the stereo to go straight to the battery and then plug the accessory wire into the stock radio plug that should fix the issue right?

Edited by PercyTheAce
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