Mike,
Sounds like you have a positive ground car.
You should disconnect and start over. It is very important
to mount the radio chassis to an insulating material such as thin plywood or
Plexiglas so no part of the metal radio chassis or knob shafts can touch the
metal body work of the car. This is easier done than described in writing.
The non-conductive adapter must be cut out and drilled for the radio to fit
into, and big enough on the outside dimensions to cover the opening of the
radio blanking plate. What I did was make two of these adapters, one for the
outside of the dash, the other for the inside. The two adapters will then
sandwich the dash metal in between. In more than 10-12 years of sporty
driving, the radios stayed put.
If the radio must be mounted directly to a metal dash, a way to prevent the
shafts from touching metal, is to slide a plastic or rubber bush into the
holes drilled to accept the shafts if present.
Another word of caution concerns the antenna. Be sure to prevent the antenna
from
grounding to the body. Some antennas are designed to have their base
touching metal; avoid that type, or make a big rubber washer out of an inner
tube, hold it to the underside of the sheet metal, then put the antenna in
place and snug things up. I have seen some "high tech antennas recently that
require no metal to metal contact. A common example is the antenna tape that
can be applied to the windshield inside surface: especially nice when you
replace a fender and choke at the thought of drilling a big hole in it.
I hope I haven't forgotten something. After installation and before
reconnecting the battery and powering up, check for continuity between the
car body and the radio chassis... there should be NONE! Install fuses in
power leads. All disclaimers apply... Yadda, yadda.
Good luck!
Jim
Tab Julius wrote:
> Don't worry about the antenna - make a point to wire from the ground screw
> (usually in the back of the radio chassis) to the body. A few new DIN
> radios have a dedicated black ground wire, and you can use that, but if
> not, make sure the body of the radio has a good, preferably thick, wire to
> the body of the car.
>
> Also make sure you're not in a positive ground vehicle (I forget just
> exactly when they changed over).
>
> - Tab
>
> At 08:43 PM 1/28/00 -0800, mistebar@juno.com wrote:
> >I was just going to do a simple project on our 1968 MGB-GT and put in a
> >radio. After seeing the comments, I think I need help. I replaced the old
> >radio with a new one using the same wiring. The light on the unit
> >"pulsates", but does not turn on. I don't know if the antenna is grounded
> >or not. When I touch the radio body with a voltmeter and ground it, there
> >is 12 volts. What am I doing wrong?
> >
> >Mike
> >
> >Mistebar@Juno.com
> >
> >http://dl.www.juno.com/get/tagj.
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