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Discussion Starter · #1 ·
I’ve been cleaning up some wires and had a quick question about powering the factory radio. Previous owner had a wire on the accessory post and I removed it.

I have the fuse taps and I was thinking it would be better to tap into the radio circuit with the tap. I haven’t yet found the original radio wires etc.

Wirthco 0303.1233 30200 Battery Doctor Roundtapper Kit https://www.amazon.com/dp/B000CQDRSE/ref=cm_sw_r_cp_api_fgSFBb176KK5B

Does that sound like a good plan? Thanks


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Can we assume that the original wire has been cut at some point and the OE plug no longer exists? If so, I would personally prefer to go to the accessory post on the ignition switch. I just went through radio wiring issues and traced them back to poor connections at wire taps installed by PO. I elected to hard wire into the radio wire using solder and shrink wrap. Mine is an aftermarket radio and never had the original plug.
 

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65-67 dealer-installed radios were connected to the threaded spike on the back of the ignition switch. You sure the wire you pulled off wasn't a Ford accessory wire?
 

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Discussion Starter · #5 ·
Sorry for the missing info.

This on a 1970 Mach 1. The factory plug wire is missing so it was likely cut a long time ago.

The wire that was on the accessory terminal was definitely from the PO and was a little ragged.

Wouldn’t tapping it on the radio fuse work correctly? It would still operate by whether the ignition was turned on, correct?


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Discussion Starter · #6 ·
Any chance this is the original radio wires? It has a blue (I think, but not sure because I am colorblind )wire, and the original radio light wire was blue...




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Discussion Starter · #7 ·
Okay so I used the accessory post for the main power and that is working correctly.

For the blue radio wire I tried tapping into the blue/red per the diagram below but I’m only getting half a volt. Where is the correct place or wire for the radio light? Did I tap into the wrong one? Thanks

https://www.fasett.info/70-mustang-...headlight-switch-wiring-diagram-turn-signals/


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The BLU/RED wire only has power when the parking or headlamps are on and the voltage varies with the rheostat on the headlamp switch.
 

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Discussion Starter · #9 ·
That’s the odd part. Even when turning on the parking and headlights, still only.5volts.

You think its a bad connection then? It’s confusing because if it were a bad connection would I see any voltage at all?

I’m not certain on tbe wire color (faded) but its across from the blue/black so I’m pretty sure I got the right one.


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I don't think that's the radio plug.... I'd expect to see a TWO wire plug with one BLU/RED and one BLK/YEL.
 

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Discussion Starter · #11 ·
Thanks Woodchuck. Just to back up a step for clarification:


1. I posted that pic earlier in the thread when I was trying to see if I could find the factory plug. Since that time, I gave up on that and ran a new power wire to the accessory circuit. I tested the voltage to that new wire and it works correctly - shows 12 volts when in accessory mode and nothing with the keys out etc. So I'm good on the main wire.


2. Now I'm trying to run a wire for the radio light. I had Gary Tayman modify my radio (AWESOME job, by the way!), and I need to find the circuit for the radio light. Using that diagram, it seems that the blue/red wire would be the most appropriate, and in the new owner's manual for the radio mod it states to use the dash light circuit. Using that wire should not only work only when the dash lights are on, but it should also dim with the dash lights when desired.
3. I used a T-tap (practiced on a piece of wire first) and I'm pretty sure it is on there securely. Since I'm seeing a half a volt I'm thinking it at least has a connection. There is a possibility that I got the color wrong (color blind) but I can clearly see the blue/black wire across from it which matches the diagram.


So - either my wiring is a bit different in the car, I picked the wrong wire, my t-tap has a bad connection, or there is something else I didn't think of.


The way I'm testing the voltage is touching the red terminal on the volt meter to my new tapped wire, touching the black to ground under the dash, and then turning on the parking lights.


Do you think I should just try a different wire like the one for the parking lights, instead? I'm okay with it not dimming, but I'd at least like to have it controlled along with the parking/headlights if possible.
 

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Palacekeeper

The instrument cluster lighting is usually a light blue with a red stripe. Do you have anyone around who can verify the color for you?

The method you are using to check the voltage is correct assuming you have a good ground. Do the instrument light come on correctly? Do they dim correctly?

I would expect to see anywhere from 0 - 12 volts depending on the dimmer position.

I’d love to see some pics of the radio and how Gary modified it. I am planning to send him mine eventually. What options did you pic?
 

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Discussion Starter · #13 ·
I’m pretty certain on the color at this point. Tried the one for headlights also. Same half volt even with lights off. Tried a new t tap (red) on the blue/red which is for 18-22 gauge, same thing. Just doesn’t make sense but I guess there’s no easy way to tell for sure if it is making a good connection inside. I even gently used pliers to make sure it was clamped all the way.

Here’s a few pics of the radio btw, got Bluetooth and line outs.



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Make sure you're checking with a good ground. Frequently there is a triple tap behind the dash to the right of the instrument cluster area for illumination. Do you have a clock? You could tap into the Blu/Red with a Scotch-Lok.

See the picture below. Any of the wires going to the illumination bulbs can be tapped into...except for the map light bulb as tapping into it will provide it with a ground and cause it to light regardless of the switch position...

 

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Discussion Starter · #15 ·
Make sure you're checking with a good ground. Frequently there is a triple tap behind the dash to the right of the instrument cluster area for illumination. Do you have a clock? You could tap into the Blu/Red with a Scotch-Lok.

See the picture below. Any of the wires going to the illumination bulbs can be tapped into...except for the map light bulb as tapping into it will provide it with a ground and cause it to light regardless of the switch position...



I think my ground is okay because the same ground is working fine when I test for 12v on the main power wire. I’m using another brand of scotch-Lok but when I tested them they seemed fine. I do have a clock, guess I could try that next.


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Not to side track the thread...

"65-67 dealer-installed radios were connected to the threaded spike on the back of the ignition switch."

True, That the threaded rod on the back of the ignition switch is an extra "Accessories" extra Power Terminal....but the Factory installed Radios weren't wired there... would think "Dealer Installed Radios" were installed the same way since they used the same identical instructions..

1965-1966 Factory installed Radios used a Red 3 Hole Female Connector (that was already under the dash), and a single Spade connector plugged into it to get power to the Radios. (See Attached pic.)

1967 and 1968 was a bit different...(Again, See Pics.)

I don't have the 1969 and 1970 Specific Radio Wiring Diagrams, but I have the "General" wiring Diagrams that include everything..

I suggest the you pick up from NPD the Osborn/Ford Factory Electrical Manuals for 1969 and 1970 Mustangs. It will have everything..

:eek:)

Tony K.
 

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Your 70 is a nonidentical twin to a 69 in most respects, but I'm told that in 70 Ford redid the harnesses and first started using fuse links, among other changes- of which I am largely unaware. I have a 69 and know the circuits very well. I suggest you do yourself a favor and go to 69Stang.com, which is a forum just for the 69s and 70s. If you and I can't resolve the harness differences the guy to talk to is Midlife. He is a moderator on Stangfix.com and owns a harness refurbishing business, and I guarantee he can answer any question you have. His website is midlife66.com, but he is often found on 69Stang.
Now if you go to 69Stang in the "How Tos" section, the first post is "A REAL Schematic". This is the only full car schematic for a classic Mustang. Don't confuse a schematic for a wire diagram. A schematic shows you how it works, while a diagram shows you how it is wired.
Page 2 of the schematic shows interior lights. You will notice that terminal "I" from the light switch goes to a 4A fuse in the block and then to the radio light among other things. Since you only have half a volt on terminal "I" can I assume that the ash tray light, heater lights, clock lights and dash lights don't work either? This sounds like the light switch is defective. It sounds like you connected to the correct wire but may have bypassed the fuse- but that isn't the reason it doesn't work- it doesn't work because the light switch rheostat is defective.
 

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@palacekeeper...did you ever get your radio to work? I just got an AM/FM radio off of e-bay and am about to send it into Gary for conversion as well. RIght now I have a retro-sound radio in the car so I think I might get very lucky and just have to do a little rewiring to what I already have. But I am curious as to where you tapped into for the radio light? I am thinking of tapping into the wire that power the light for the heater/ashtray lights. Thanks
 

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Discussion Starter · #19 ·
@palacekeeper...did you ever get your radio to work? I just got an AM/FM radio off of e-bay and am about to send it into Gary for conversion as well. RIght now I have a retro-sound radio in the car so I think I might get very lucky and just have to do a little rewiring to what I already have. But I am curious as to where you tapped into for the radio light? I am thinking of tapping into the wire that power the light for the heater/ashtray lights. Thanks
I never did power up the light, actually. It just got to be too confusing tbh. Electrical wiring is by far my weakest area. Although I did do a good job fixing my ignition wiring recently, so maybe I’ll go back and revisit it in the Spring. If you are successful with it, reply back with what you did, and I’ll do the same if I get mine straightened out.


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