Amp question on a 65... (1 Viewer)

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DomSmith

DomSmith

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Thought I'd try the electro tech's here first.

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 like it's going to cut out then immediately back to normal. EDIT: Only the first draw... so as the turn signal is switched it cuts then stays normal even though the blinker is blinking.

I have a good battery, good grounds and a new OEM fuse block.

Any suggestions?

Thanks.
 
Last edited:
Are you absolutely positive the ground is good...have you tried running a jumper cable directly to the frame from the negative lug of the amp?
 
Hmmm...what are you running the power wire off of, I'm betting it isn't coming straight from the battery. My thinking is that you're running through the fuse block and the block is experiencing a momentary amp draw whenever the brakes/turn signals are applied. It could even be that the fuse block needs better grounding....

My two edumacated guesses are a bad amp ground or interrupted power due to possibly a poorly grounded fuse block or a malfunctioning fuse block. Since your amp ground is good, it must be the latter so try running your power wire straight off the battery and see if that fixes it. If it does, I'd say to run your amp power wire straight off the battery with a fuse as close to the battery as possible, and investigate the fuse block amp draw when you have the time.
 
Thanks 46. Power is run straight from the battery with large gauge wire and a fuse about 12" from the terminal. Then a much smaller wire comes from the switched side of the fuse block to the "REM" spot on the amp. If I move that wire over to the battery side of the fuse block too, there's no change (except it has power all the time).

I just replaced the fuse block with a brand new OEM block but I'll ground that straight to the battery to test the ground there. How do I test amp current from the fuse block? I don't see a setting on my sunpro multimeter...

I'm not so good with electronics but could my points style voltage regulator have something to do with it? What if my alternator is putting out low amps?
 
Well I decided to change out the negative battery cable just to be sure but no real difference there.

I did take a little more time trying to figure out what is going on and found something interesting. 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.

:confused:
 
I'm not totally clear on how you're running your power line, does it go to the fuse block first or right to the amp?

This would be my set up for testing purposes:

Power from battery straight to amp +
Negative from chassis straight to amp -
Power from battery straight to amp REM

In this setup, your amp will be running straight from the battery with no interruptions and no connection to the fuse block. As long as you're running regular door speakers and not 10" subs or bigger, the turn signals/brakes should have no effect at all on the amp since it's completely independent.

Since you said your REM is coming from the fuse block, my current guess is that when you hit the turn signal/brake, there's a momentary dip in power which makes the amp think that you're turning it off via the REM wire. Since it happens so fast, the amp doesn't power all the way down hence just the momentary lowered volume.

Take the fuse block completely out of the equation and your problem should go away. If not,it makes me think your battery is on it's way out (unlikely).
 
DomSmith said:
Well I decided to change out the negative battery cable just to be sure but no real difference there.

I did take a little more time trying to figure out what is going on and found something interesting. 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.

:confused:
Click to expand...

That's kinda weird....
Set your voltmeter to volts, connect it to the amp power input, and see if the power from the battery to the amp stays constant throughout.
 
46/71 Hybrid said:
Since you said your REM is coming from the fuse block, my current guess is that when you hit the turn signal/brake, there's a momentary dip in power which makes the amp think that you're turning it off via the REM wire. Since it happens so fast, the amp doesn't power all the way down hence just the momentary lowered volume.

Take the fuse block completely out of the equation and your problem should go away. If not,it makes me think your battery is on it's way out (unlikely).
Click to expand...

46-

I jumped the REM to battery instead of to BATT through the fuse block and it seems to have isolated the problem. So... I need to figure out why I'm getting a small power drop through the fuse block. Or come up with another solution.

1. Can I use a larger gauge wire to the REM? It's currently small (maybe 12 or 14 gauge). Would that solve the issue? It's currently going out the firewall down to the frame and up in through the bottom of the rig and to the amp.

2. I suppose I should look at my wiring diagram and clean all the wires connected to the battery (ie: ignition switch/alt/starter/coil/fuse block) and clean them up?

Any other suggestions?
 
That's good news, now we see that the fuse block is the issue. I'll list my ideas in point by point format since the kids are running around and I don't want to start rambling.

#1) The REM wire size should be sufficient, this wire usually comes off the head unit whose wires are smaller than 12 gauge. It's just used to trigger the amp and let it know that the radio is on. This wire is more about volts than amps and doesn't need a large size to carry current.

#2) The wires to the battery shouldn't be the problem either although cleaning them and double checking the connections certainly won't hurt.

#3) My guess is that your fuse block doesn't have a good ground and when you flip the turn signal/brake, a tiny arc jumps which causes it to momentarily lose power, then stabilizes itself enough to keep power flowing. I would triple check the grounds to the fuse block and if need be, run an extra wire from the fuse block to the frame. Just to be sure, I'd also double check the ground from the batt to the frame and maybe even run an extra ground wire.

Your other option is to wire up a switch that's connected to the REM line so you can turn your amp on and off as you please. The wiring for this would be Batt-fuse-switch-REM. (you can substitute Batt-fuse for the power line that you're already running from the batt, just tie into it).

Eventually though, you'd still have to find the poor fuse block ground or you run the danger of losing what little ground you have and the brake lights/signals stop working.
 
46/71 Hybrid said:
#3) My guess is that your fuse block doesn't have a good ground and when you flip the turn signal/brake, a tiny arc jumps which causes it to momentarily lose power, then stabilizes itself enough to keep power flowing. I would triple check the grounds to the fuse block and if need be, run an extra wire from the fuse block to the frame. Just to be sure, I'd also double check the ground from the batt to the frame and maybe even run an extra ground wire.
Click to expand...

I don't think I have any grounding wire to the fuse block. It's bolted to the firewall and I ran a jumper from the metal base of the fuse block to the battery without change...
 
That's a bummer, I typed a reply earlier and now that I'm checking to see if you replied, I see that my earlier reply isn't even posted.

Rather than re-type it all, I'll sum it up by saying that the problem either has to be a bad ground or a draw in current when you activate your brakes/signals. My guess is still going back to the ground, is the block mounted on bare metal or is the firewall painted? There's no place for a negative cable to run to the fuse block? Also, do you have fuses or relays for the turn signals? Could be that a relay is going out....

Try this; Insert a stripped wire under the fuse block and run the other end to the neg side of the battery. Tighten down the fuse block so that it squishes that wire between the fuse block and the firewall. That should guarantee a good ground.

Now that we have a supposed good ground, double check it by using your voltmeter and checking your volts with the neg lead on the metal base of the fuse block and the pos lead on a pos point of the fuse block (try swapping the pos lead to the pos battery post also). Are you seeing 12 volts? Now have someone flip a signal or hit the brake pedal...did you see a dip in the 12 volts? If so, try the same thing but this time put the negative lead to the battery. If you're still seeing a dip even with the neg lead on the battery, your problem is the power wire to the fuse block. <<--This is unlikely though unless you're using a frayed old wire or the gauge is too small. What size pos wire are you running and is it new?
 
Not much time to work on this but, the fuse block trick changed nothing so I think it has a good ground. After cleaning up the dash turn signal bulb holders it helped so I'm going to try and get the rear lights off and re-ground them. I did assure good grounds at the front bib lights/turn signals/headlights already.

I also fixed the grounds at the battery/starter/mid-frame/and bed to frame without any improvement. But now I know they are all to fresh metal.

I'll be installing new ALT/VR/Coil Saturday and then those will be out of the equation (I hope).
 
I don't think it's the alt/vr/coil since it presumably does it while the car is off too, right? My guess now is a turn signal socket that's causing the trouble, especially since you said you cleaned some of theme and it helped.

This is interesting....
 
46/71 Hybrid said:
I don't think it's the alt/vr/coil since it presumably does it while the car is off too, right? My guess now is a turn signal socket that's causing the trouble, especially since you said you cleaned some of theme and it helped.

This is interesting....
Click to expand...

Yes. Everything should work without the rig running so these items have no bearing.

The reason I'm replacing the alt/vr/and coil is that the alt was putting out 5 amps, the VR was up to 16+ volts and my points are scorched (no ballast resistor). These don't have much effect on this situation but will help the electronics overall.

I agree. After messing with the turn signal stuff I'm thinking opening up the tail lights and cleaning them up completely may make some progress.

:beer:
 
So you're saying if you run both the Power and REM right off the battery, the amp still trys to turn off when you hit the turn signals? If that's the case, I have to guess that your batt is the problem, although it's HIGHLY unlikely.

Now this is confusing and interesting, I've never come across anything like this before...
 
46-

This has to be an amp problem or bad wiring that is not visible from inspection. When I get a chance I'm going to pull it all and probably get a new amp. If I decide to use this I'll do a quick short leg install before running everything permanently.
 
What I can't figure out is how the amp knows that your turn signals are on? Once you have the amp hooked directly to the battery, you basically have a stand alone system since the speakers and signals have nothing to do with each other.

I wonder if one of your speakers has a bad ground? Even then, the amp still shouldn't know when the turn signals are on, know what I mean?
 
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