Is there a way to have the stock am/fm radio and an aftermarket am/fm cd/mp3 deck to be able to share the same speaker and power connections?

Here's the situation. My cousin has an automatic 98 Civic DX. My uncle has gout in his leg and can no longer drive stick, so he will also be using my cousin's car. Right now there's just the stock am/fm radio, which happens to have a built in clock. My cousin wants me to put an aftermarket mp3 deck in the DIN slot by the cupholders, so that it will be out of sight from any potential thieves. With the aftermarket deck installed, the stock radio will be rendered useless (no clock) since it will be disconnected from the power. With the aftermarket deck mounted in a much lower position, it would be harder for my uncle to reach down and fiddle with the mp3 deck, and the cupholder area is not an ideal place for a clock. I'm wondering if it is possible at all to have the stock deck and mp3 deck hooked up to the speakers and power simultaneously. I know it sounds gay, but my cousin asked me if I can set it up that way since I will be the one installing the mp3 deck.

 

Yes it is possible, you will need to "switch" the speaker outputs on the two units, they can NOT be hooked up to the speakers at the same time, although I do not know of anyone that still makes a "radio tape deck switch", they where very common 10 years ago, but you could make one, all you need is two 4PDT 12V relays and one SPDT 12V relay http://sonolithics.com/files/bosch.pdf although a switcher is probably the only thing the do not have hear, and everything hear is SPDT relays, it is a good place to learn to understand how relays work, a 4PDT relay is nothing more then 4 SPDT relays in one case, there is also good info on relays at http://www.the12volt.com. feel free to IM me if you need more help 94

 

So in essence, it will be similar to 2 computers using a KVM switch...I'll check out radio shack. Thanks for the info.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by White95SiHB &raquo;</TD></TR><TR><TD CLASS="quote">So in essence, it will be similar to 2 computers using a KVM switch...I'll check out radio shack. Thanks for the info.</TD></TR></TABLE>Ahhhh maybe, as I know diddly squat about computers, but what you will be doing is isolating all 8 speaker wires 4 pos. and 4 neg., that's what the 2 4PDT relays are for, the speaker wires will be wired to the common term., [30] of the relays, and the speaker wires of the oem HU will be connected to the N/C "at rest" term. [87a] of the relays, and the speaker wires of the aftermarket HU will be connected to the N/O term. [87] of the relay, keeping all the same wires on the same poles.
The SPDT relay, [optinal] would be used to switch power on the oem HU, [turn it off] you would cut the acc. wire to the oem HU and connect the power side to 30 of the relay and the HU side to 87a, so when relay is at rest the oem HU would get power, you would ground 85 of the relay and connect the blue/white, [amp control lead] of the aftermarket HU to 86 of the relay and 87 of the relay would go to 86 of the two 4PDT relays, with 85 on them being grounded, that way when you turn on the aftermarket HU it will turn off the oem HU and switch the speakers to the aftermarket HU. 94

 

So if the OEM headunit gets switched off, will it be like you're turning the radio off, or will it be like the radio is being disconnected from the battery? If it's like the latter, that means the clock will have to be set everytime it's turned on.

 

No, it would be like switching off the oem HU, as the SPDT relay is only on the acc. line to the oem HU. 94

 

Let me see if I understand this correctly. The 8 speaker wires from the OEM/HU go to one of the 4pdt relays, and the 8 speaker wires from the aftermarket/HU go to the other 4pdt relays. The SPDT relay is connected the power, a switch, and the other 2 relays.

Please bear with me, this is all new to me.

Thanks in advance.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by White95SiHB &raquo;</TD></TR><TR><TD CLASS="quote">Let me see if I understand this correctly. The 8 speaker wires from the OEM/HU go to one of the 4pdt relays, and the 8 speaker wires from the aftermarket/HU go to the other 4pdt relays. The SPDT relay is connected the power, a switch, and the other 2 relays.

Please bear with me, this is all new to me.

Thanks in advance.</TD></TR></TABLE> No, all the speaker wires from both units and the speakers go to both relays, and you will have to bear with me, as I have not figured out how to draw on "paint" and then transfer it here yet, but let me try and explain, if you understand how a relay works, [a SPDT one] the 4PDT is just 4 SPDT relays in one package, and because you have 8 speaker leads you need 2 4PDT relays, as the speakers are common for both the HUs they would be connected to the common term. of the relay, [30], it makes no diff. on what term. you put what speaker lead, [you can put all the neg. on one relay and all the pos. on the other, or the fronts on one and the rears on the other, lefts on one and rights on the other , or totaly random]
Now you wire the speaker leads from the stock HU to the NC term. [87a] You can no longer be random about which wires go to what term, they have to line up. If you have the RF speaker pos. connected to 30 on the first pole of the first 4PDT relay then you must connect the RF speaker pos. output of the stock HU to 87a of the same pole on the same relay, and so on, with rest of the wires.
Now connect the speaker output wires of the aftermarket HU to the NO term. [87] of the 2 4PDT relays, again lining them up in proper order.
The SPDT relay will be used to switch the acc. power on the stock HU, the constant power is wired directly to both HUs, the grounds are wired directly to both HUs, the illumination is wired directly to both HUs, [if they have an illumination input] The acc. wire from the cars harness gets wired to the common term., [30] of the SPDT relay, and directly to the aftermarket HU, the acc. wire from the stock HU is wired to the NC term., [87a] of the SPDT relay, cap off term. 87 of the SPDT relay so it can't short out, in fact all term. of all 3 relays have to be insulated to keep them from shorting out, [I use shrink tube].
Terminal 85 of all 3 relays, [one side of relay coil] goes to ground.
Terminal 86 of all 3 relays, [ other side of relay coil] are connected to the amp. control lead of the aftermarket HU, [probably blue/white]
When you turn on the aftermarket HU it will trigger the relays, turning off the stock HU and connecting the speakers to the aftermarket HU, when you turn it off the stock HU will come on and the speakers will connect to it, [relays at rest.]
This job will be made a lot easier if you pick up the adpt, harnesses, Metra P/Ns 70-1720 and 71-1720, all connections and soldering can be done on a bench. 94

 

yes it is the same idea as a KVM switch. you dont wanna backfeed power from one to the other.
The easiest solution would be to buy a radio with a remote and ur uncle can use the remote so he doesnt have to lean way down.