Chevy Astro and GMC Safari Forum banner
1 - 20 of 23 Posts

·
Registered
01 Astro RWD Cargo, 97 AWD Mark III
Joined
·
2,210 Posts
Discussion Starter · #1 ·
My 97 Mark III conversion has 2 radios in it. The normal dash mounted unit and an additional rear mounted unit in the grannies attic of the high top. To me this is redundantly stupid.

I am not electronically savvy enough to figure this out on my own. I can make expensive mistakes!
Would it be possible to wire up the dash radio to run some kind of relay system off the house battery as well as the normal key key hot?

What I am thinking is the normal key hot for driving. Then once parked and in camp/tailgate mode. Flip a rocker switch to power the radio off the house battery.

The head unit is a PYLE PLTS78DUB 7" TOUCH SCREEN CD/DVD/MP3 Car Player w/USB SD AUX Receiver and I will be using the Metra 70-1858 GM4001 GM Wire Harness to install the new head unit. Any connections can be made in this harness. This may include my Kenwood 10 disc changer (not sure on compatibility yet).

Eventually the plan is to include an Xtrons cm195hd 19.5" Flip Down Car Roof Monitor Ceiling Overhead HD TFT 1080P Screen which will be strictly powered off the house battery but will need a toggled relay to break power when not in use.
 

·
Registered
1998 LS AWD Forest Green metallic
Joined
·
1,105 Posts
Yes, It is definitely possible!
You probably have more than one power lead to the radio. One for memories and the clock etc, which will be powered (hot) all the time, even when the radio of OFF .
You are working with a non-stock radio, so this is just a general guide.
A simple SPDT (single-pole double-throw) toggle switch will work. That is one that normally has three terminals.
One will be a 'common' lead, and the other two are the two outputs( or two inputs, depending upon how you are using it), selected by the position of the switch.
All you need to do is find the wire that powers the radio ( turns on and off with the key switch). It needs to be connected to one side ( output) of the switch. The wire from the is to Aux battery needs to be connected to the other (output) side. the two 'outputs' are actually being used backwards, becasue they are actually being used as power inputs, but it will not affect the switch opertion or life. The original wire to the radio will go on the 'commom' terminal ( the one that gets switched from one terminal to the other when the switch is activated)
Purchase a good quality toggle switch, rated at the power you need to run your radio. If it is a high powered radio, get one rated for at least 15 amps. It is still a very inexpensive and very basic switch .
Rod J
 

·
Registered
01 Astro RWD Cargo, 97 AWD Mark III
Joined
·
2,210 Posts
Discussion Starter · #3 ·
An SPDT was just what I was thinking for the toggle. I just never thought of reversing and using it as line in instead of line out. That will greatly simplify the task.
 

·
Registered
Joined
·
92 Posts
Not an electrician by any means, but I recently swapped my aftermarket radio to run off only my house batteries. Originally planned on doing what you want to, but ran into issues with the constant hot still drawing off my starter battery. That was fine when running, but when engine off, power for the radio is still coming from the starter battery. Which was the whole point of not wanting that to be the case when I was sitting.

I was told the constant 12v is what's powering the radio, the memory and possibly other power drawing devices. All the acc 12v wire is doing is turning the radio on and off. Not sure how much of this is actually true, but my installation experience led to issues where power was coming and going. I ended up transferring ALL 12v from the radio directly to my house batteries and an on/off switch. Even then my backup camera power wire, was, I assume, back feeding the radio so that if I turn my vehicle off with the camera "on" , the radio will stay playing with the engine off and house battery 12v acc. switch off.o_O

Now maybe I screwed something up, but I can only suggest that after making any changes, checking the voltage on every radio power circuit so you know where power is going and where it's actually being drawn from under different conditions..
 

·
Registered
1998 LS AWD Forest Green metallic
Joined
·
1,105 Posts
An excellent suggestion,particularly since what you have is not an original radio installation ( It may not have been wired in the way it was supposed to be).
Your radio should be very happy running off the Aux battery all the time, as long as the Aux battery gets recharged regularly ( as in, whenever the motor is running) .
Rod J
 

·
Administrator
Common Sense + Critical Thinking
Joined
·
13,078 Posts
The only downside of having it powered from the house battery all the time is that allows less power for charging. With my temporary house battery setup in BB, I have 20amps available to charge the battery, so if my fridge is running, and my phone is charging, and my... you get the point, there is less power available to actually charge the battery. During the summer I would switch the power from the house battery to the rear aux while I was driving longer distances, which allowed the fridge to run directly from the alternator instead of the house battery, allowing the battery to use the full 20amps to charge.
I have thought about adding an ACR to automatically switch the fridge/etc so it's powered by the vehicle while it's running. Haven't gotten there yet.

Also, have a look here:
 

·
Registered
Joined
·
92 Posts
I'll admit I gave up pretty quick on trying to incorporate having the radio being controlled with both the key and a switch. Given my extensive knowledge of electronics and a "hold my beer" attitude of doing things, I knew was asking for problems trying to solve the issue. Since I've kept all of my other electrical addons separate from any of the OEM wiring as to isolate any problems(or fires)...I figured it was my safest option.:D

I do agree battery charging/capacity needs to be factor with such endeavors..In my case, I have sufficient house power and charging. where I don't have any issues even with my fridge running 24/7 in the background. I'll still be interested in how Ghost ends up accomplishing what he wants to. I used 2 of the lighter plugs for my install 1 for the on/off and one for the USB port. the Carplay jack I just fed through the ashtray for now.
Vehicle audio Personal luxury car Steering part Vehicle Center console
Car Vehicle Automotive design Personal luxury car Fixture
 

·
Registered
01 Astro RWD Cargo, 97 AWD Mark III
Joined
·
2,210 Posts
Discussion Starter · #9 ·

·
Administrator
Common Sense + Critical Thinking
Joined
·
13,078 Posts
That could work on barn door, But dutch door uses that for the release switch.
I'm not sure what years/models had that switch, none of mine do.
 

·
Registered
1998 LS AWD Forest Green metallic
Joined
·
1,105 Posts
IDK about other years, but the 1998 did not have a dutch door rear hatch release up front.

Rod J
 

·
Super Moderator
05 Astro AWD
Joined
·
14,134 Posts
I'm not sure what years/models had that switch, none of mine do.
1997 and down use the hatch release inside. The 1998 and later only releases the latches while the release is pressed, so it can’t be done remotely.
 
  • Like
Reactions: AstroWill

·
Registered
01 Astro RWD Cargo, 97 AWD Mark III
Joined
·
2,210 Posts
Discussion Starter · #13 ·
So, Obviously a common setup in the RV industry. A couple bits from the RV Forum.

Battery selector switch for in-dash stereo?

"the radio is powered from a relay, normally connected to the house batteries but when the ignition is turned on, the relay switches to chassis power. There is a separate wire for the memories"

And

"Our Tradewinds uses a double pole double throw switch to select the stereo while driving powered off the hot side of the ignition bus (Radio stays on when M/H is shut down).

The other throw is marked TV/Stereo and uses power from the coach batteries. The reason for the double pole is that when powered from the coach the output not only goes to power the stereo but also powers the FM Modulator that feeds audio from the TV into the stereo system.

By using separate power when driving the modulator is off and does not interfere with the stereo freqency utilized by the modulator.

The memory power is wired to the chassis hot bus with an inline fuse."
 

·
Registered
1998 LS AWD Forest Green metallic
Joined
·
1,105 Posts
As for accessory power outlets ( the ones that look like cigarette lighter outlets), I would suggest not using them for anything that draws over 8 to 10 amps ( some refrigerators are in the 8 amp range) . Most of the outlets are not designed for prolonged use at near the maximum current rating, even with excellent quality plugs. I see many plugs that get quite warm under long term use at 5-8 amps. Some ham radio operators try to power their radios (10 to 12 amp loads when transmitting) from those outlets. Plugs often work loose, and heat is often generated, even when they stay in place.

The wire to the rear power socket in my 1998 appeared to be quite small. I looked at the wiring schematic, and it is a 1.0mm wire. That is slightly smaller than 18 (#19?) gauge. That size wire is 'protected' by a 25A fuse. IMHO, that is a very marginal design. Most wiring charts call for a minimum of a #14 wire, for a 10% voltage drop in anything less than a 10 foot run, with a 15 amp load.
I found the wires to the sockets in the right side of the console were similarly small for the application ( my opinion)) . All are supplied by the same 25A fuse ( the same fuse also powers the Sub-Woofer amp) , so do not attempt to get much power from all of them at the same time.

The fuse (#13) that supplies power to the actual cigarette lighter outlet is a 20A and that is a 0.8mm wire ( close to #20 wire). It also supplies power to the front door lock switches, the convenience center, and the rear hatch lock switch. Since all of those circuits are either low power or very intermittent, the #20 is probably adequate, if undersized by some standards.
Many of the accessory power plugs are poorly made, and do not provide a solid contact in the sockets. The end result is heat.
Be careful with ad-ons!:cautious:

End of rant!
Rod J
Issaquah, Wa
 

·
Super Moderator
Joined
·
14,360 Posts
Use a relay. It would switch from house battery to start battery when you start it. Relays have normally closed and power activated. Run normally closed to the house battery and the other to the keyed hot. Instantaneously switching it. Keep the memory wire on the start battery so there is no interruption. It is on 24/7 it isnt draining anything.
 

·
Registered
Joined
·
92 Posts
Use a relay. It would switch from house battery to start battery when you start it. Relays have normally closed and power activated. Run normally closed to the house battery and the other to the keyed hot. Instantaneously switching it. Keep the memory wire on the start battery so there is no interruption. It is on 24/7 it isnt draining anything.
I read the link in Ghosts but admit I don't understand much of it. I understand what you're saying about how to switch back and forth between keyed/house on and off and the memory not drawing much of anything when either/both are off. But I'm still not convinced in newer radios at least, that the memory wire isn't actually what is powering the radio itself. It wasn't the case in my in situation.

What you say maybe correct, but I'm still under the impression that even if you switch to your house battery to turn on/off your radio, it will still be the starter battery that the radio is going to draw/drain from because the memory wire is still only connected to the starter battery in either situation. As I say, I may be wrong, a haven't found anything to verify if that is always the case.. But FWIW, I did read that's why in newer units the memory wire is actually a large gauge compared to the 12v acc wire just because of that, which is also the case in mine.. :unsure:.
 

·
Registered
01 Astro RWD Cargo, 97 AWD Mark III
Joined
·
2,210 Posts
Discussion Starter · #17 ·
It is simple to understand that the memory circuit is 12v constant and the power circuit is 12v switched, It is the 12v switched circuit that turns the radio on/off. You are likely confusing the stay on circuit with the memory circuit.
 

·
Registered
Joined
·
92 Posts
It is simple to understand that the memory circuit is 12v constant and the power circuit is 12v switched, It is the 12v switched circuit that turns the radio on/off. You are likely confusing the stay on circuit with the memory circuit.
No I don't think I am. The memory/constant 12 wire is yellow and the 12V acc./keyed switch is red in my case. Again, in my case the red 12v wire is what turns the radio on or off whether it is connect thru the OEM key wiring or the switched house battery. But If the yellow(constant 12v/memory) stays connected to the OEM wiring , once the radio is turned on, it will draw it's "playing" power from the yellow/constant and hence the starter battery regardless of which battery the switched wire (red) is connected. I understand it will still work like that, but doesn't accomplish the radio of only playing off the house batteries when the vehicle is turned off.
 

·
Registered
01 Astro RWD Cargo, 97 AWD Mark III
Joined
·
2,210 Posts
Discussion Starter · #19 ·
Easy enough to prove/disprove. I will leave the 12v constant disconnected when I wire up the head unit. If the radio works then the 12v constant is not the power supply for operation.
 

·
Registered
Joined
·
92 Posts
I'll be interested in your results. I just checked my system again.

With the 12v constant(yellow) disconnected and 12v acc.(red) powered, radio will not work.
With 12v acc.(red) not powered and 12v Constant(yellow) powered, radio will not work.
With power to both 12V constant and 12v acc, killing power to12V constant, the radio shuts down.

Based on other systems, I'm sure there is a work around(probably relays?) that will transfer both 12V wires from ignition power to house power. thru switching the key off if desired.
Since my main reason for messing with my system was to power my radio solely off my house batteries when sitting, I transferred both to bypass the ignition and OEM wiring all together. using a toggle switch to the 12V acc. to turn it on and off and have the 12v constant being fed by a separate power wire coming from the same house batteries.

Downside could be leaving the radio on for a really long time and draining the house batteries. But in my case with plenty of batt. capacity and solar charging, it's unlikely to happen..
 
1 - 20 of 23 Posts
Top