Amp question on a 65...

[DomSmith]

I hate to cross post but am not getting a lot of views in the electro forum so here goes:

Recently acquired a 1965 FJ45 (bone stock) and decided I need some tunes. So I added an AMP under the seat running to 2 speakers behind the seats. Plug in my IPOD and I have tunes! Problem is, when I hit the turn signal, brake pedal, or any draw it lowers the volume (for 1/2 second) like it's going to cut out then immediately back to normal. But only the first draw... so as the turn signal is switched it cuts then stays normal even though the blinker is blinking. As I switch the lights it cuts then stays normal with the lights on. Running or not with the ignition "ON" it's all the same.

Amp is wired right to the battery with fuse and large gauge wire with a switched power to the fuse block. I believe there's a good ground to the amp as I have jumped to the battery for ground to test that. New OEM fuse block.

EDIT: Oops... forgot to add this too:

When I first turn on the key the music plays fine through the first couple of initial loads (say two to three blinker on and off's) then the volume lowers on the fourth and it gets progressively worse. Same thing with the rig running.


Original thread here:

https://forum.ih8mud.com/electronic-toys/265373-amp-question-65-a.html

Thanks

 

[bsmith123]

ground

Try running the ground straight to the battery as well and see if it stops. I wonder if you might not have a small short in the light circuit somewhere.

 

[bphilips09]

Though this doesn't really solve your root problem, you could buy a car audio capacitor to band-aid the issue.

I'm not a car audio pro, but I believe that would work. How long is the ground wire from the amp to the grounded point? Is it the same gauge as the power wire?

 

[DomSmith]

Try running the ground straight to the battery as well and see if it stops. I wonder if you might not have a small short in the light circuit somewhere.

bsmith-

Already jumped the ground with no change. The light circuit issue is intriguing. I assumed it was with any electrical load but I just tested the wipers and it doesn't happen with them...

Not sure why it would be fine the first few times, then the third time or so it starts. Each time I cycle the key off then on, it's good until the third draw or so...

 

[DomSmith]

Though this doesn't really solve your root problem, you could buy a car audio capacitor to band-aid the issue.

I'm not a car audio pro, but I believe that would work. How long is the ground wire from the amp to the grounded point? Is it the same gauge as the power wire?

My brother suggested the capacitor but I'm not very familiar with them.

The ground wire is BIG and about 18" and the power wire is VERY BIG.

 

[Pin_Head]

That's a pretty bizzare problem. Maybe it is a "feature" on the amp. It may detect a transient on the power line and go into some kind of protective mode. Does it mention anything in the manual? You might try a filter cap on power line and make sure that the preamp lines are shielded cable (they usually are).

 

[DomSmith]

Thanks for taking a look Pin_Head. I'll dig up the manual tomorrow. Filter Cap meaning filter capacitor?

 

[bphilips09]

My brother suggested the capacitor but I'm not very familiar with them.

The ground wire is BIG and about 18" and the power wire is VERY BIG.

I recall when I worked with my local car audio place for my college car that the ground wire should be as short as possible and grounded to bare metal on the frame of the vehicle. I think mine was maybe 5-6".

Capictors:

Info - Understanding Car Audio Capacitors

Purchase - Capacitors at Crutchfield.com

 

[bsmith123]

shorts and electronics

One thing I know for sure is that shorts do some weird things when you mix them with electronics. You can count on weird symptoms and/or unpredicatble behavior

That is of course if that is the prob

Seems like if you ran both power and ground to the batt though that should of solved the prob if it was a short


Maybe it is picking up something from the fields in the operating circuits like the lights ---In that case the shielding would be more of an issue

Do your shields go to a case ground or are they "floating"

Maybe a ground loop issue?---Also have a read here
http://www.epanorama.net/documents/groundloop/basics.html

 

[joeyg1973]

I suspect that the little 30 amp or less depending on it's age alternator you have is getting clobbered when you initially turn on the probably decades old turn signal ticker that is inefficient with very bad contacts and it is sucking down a boat load of amps just to get the initial spark. Once it gets it's initial big jolt of amps to warm up and get going, it is then only drawing very little.

Cheapest fix would be to try a new turn signal ticker.

Best solutions would be to replace the turn signal ticker and also replace the alternator with a GM CS-140 or at least a newer LC alternator.

Joe

Edit: I really need to read more... I think it is your alternator is on it's last legs or the charging wire connecting to battery is crap... I bet the battery is barely charged amp wise. Probably can't continuously run the starter for 10 - 15 seconds before it starts to bog down. The reason you don't notice this is because it is probably starting right up and the battery has just enough initial amps to get it going. Try to hook up a battery charger and charge the batter for a few hours and see if that fixes the issue. If you have an battery charger with a start function, just hook it up with the engine off and see if that fixes the issue. If it does then the cheapest fix would be to try replacing the wire from the alternator to the battery. If that doesn't fix it replace the alternator. If that doesn't fix it have the battery checked out and replaced if needed. Finally if that doesn't fix it you are up the creek without a paddle and you probably need to replace the whole harness which is a heck of a lot easier than hunting down a short.

 

[DomSmith]

Well, at the suggestion of 46/71 Hybrid I removed the fuse block from the equation and it went away. I had been jumping the REM to BATT power through the fuse block rather than straight to the battery. My bad.

So I need to figure out why there's a loss that's affecting the BATT power at the fuse block.

Could a small (12-14 gauge) wire to REM with a long leg (6+ feet) have an affect on it? Maybe just go with a larger gauge wire to solve the drop?

 

[Coolerman]

I think Pin_Head nailed it. A lot of amps have low voltage protection built in. This forces the amp into low power mode or cuts out the sub woofer drive resulting in lower volume when it detects low voltage input. A lot of amps will just shut down when the voltage drops below 11 volts.

Time to start at the battery and work your way to the fuse panel cleaning EVERY connection to bare metal. Pay particular attention to ALL the connections on the fuse panel, including the ones on the back. Especially the fuse clips themselves!

Another possible, though maybe far-fetched idea:

Light bulbs have high inrush currents, especially when the filaments are cold. The voltage will drop as the current goes up, until the filaments warm up. This might explain why it works after the first power up of the lamp(s) The filaments are now a bit warmer and have less inrush current.

 

[DomSmith]

Thanks guys I'll start working my way to the fuse panel. FWIW it's a brand new OEM fuse panel and all the wire terminals were cleaned up to bare metal at the block. I'm going to look at other connections.

 

[DomSmith]

Put a voltmeter to the fuse block and it drops just below 12v (11.93) on switch activation. Doesn't seem like enough to activate a low voltage protection.

Nothing in the amp manual about it either but that's not to say there isn't. So I guess my next question is what will cause the voltage drop through the fuse panel but not from the battery? Bad connections anywhere in the rig?

 

[joeyg1973]

What are the Amps? Almost all 12v equipment is rated to run on between 8v and 16v so a volt reading isn't telling you anything. Find out what the minimum amount of amps the amplifier takes to power. Get an amp reading from the power supply to the amplifier power input and I bet it will peak around this number with a good rocking tune playing at full volume. You don't have a pink noise generator so a rocking tune will have to do. When you turn on the turn signals or the lights I bet you see the amp reading drop at the amplifier.

 

[Pin_Head]

Chances are it is a bad connection or too small wire upstream (toward the battery) from the fuse block. That is the only way you would get a voltage drop when you turn on anything that runs off a different fuse.

 

[cruiserbrett]

I know this is a little late, but there is no way a battery that can start the truck should be drained enough by blinkers to cause the amp(connected to the battery)to start drawing down the battery after 4 or so flashes....

So, I agree with PH. there is some other issue upstream of the ammeter(or the ammeter itself?)that is causing the issues. While the ammeter is nice, try taking a 4 or 5mm screw and nut and bypassing it for a test. not sure if there are loose nuts on the buss bar inside the ammeter gauge itself, but some thing is not right...

 

[shelfboy1]

make sure the gound wire from the engine to the frame is there.goes from starter bolt to frame and make sure its tight and clean.also the voltage regulator has some adjustment to keep the altenator working .try running the truck then pull the neg off the battery .if it stays running put a load on it like lights and see if it dies.if it does you need some adjusment or new parts good luck

 

[DomSmith]

Sorry guys stuck at work for a few days. I did redo the ground wires (battery/starter/mid-frame/bed to frame) and the stereo ground. I also cleaned up the dash turn signal bulb holders and assured a good ground on the front bib/headlights. I think it helped with the turn signals. I'm going to try and remove the rear lights (I need to source the bolts as they are rusted together) and clean them up and I think that will help. I'm hoping that will take care of the drop in the lights and brake pedal.

New alternator, voltage regulator and Toyota coil will be installed Saturday.

 

[46/71 Hybrid]

Just happened across this thread, I didn't realize you posted twice in two different forums. Now that you're seeing the voltage drop at the fuse panel, we're still on track to figure this out.

Questions:
If you put the voltmeter positive on the + wire going to the fuse block and the negative on the battery, do you see a drop in voltage when you turn on an accessory?

If you put the voltmeter positive on the + battery and the negative on the base of the fuse block, do you see a drop in voltage when you turn on an accessory?

Do you have a big enough clamp (welding clamp) to grab both sides of the fuse block? If so, run an actual jumper cable negative from this clamp to the - battery. Now, if you put the voltmeter + to the fuse block + input and the voltmeter - on the fuse block base, do you see a drop in voltage when you turn on an accesory?

As far as the comment on 11.93V triggering low voltage protection, the REM wire only functions to tell the amp that the radio is on. Once that 12V is cut, even partially, the amp thinks the radio is off and turns itself off. Many amps have a 1-2 second delay before turning off but apparently yours is near instantaneous.

What kind of amp do you have and how many watts is it rated for? This question is more out of curiosity.