Hood Bond?

BWhitmore · 2014-01-05 16:45

In looking at Service Bulletin 342 about radio interference it mentions inserting a "hood bond" between the bottom of the radio chassis and the top of the ashtray. I have never heard the term "hood bond". Could this be the rubber strip on the cowl that seals the back of the hood?

Thanks

hiball3985 · 2014-01-05 18:26

Bill,
The hood bond is a metal V shaped spring type clip the best I can describe it. Some cars had them mounted on the top of the cowl and it contact the hood when closed and help insure the hood was grounded. What the service bulletin is suggesting is using this same clip between the radio and the ash tray to insure the radio chassis is grounded.. Static in the radio is usually caused buy the generator but you have an alternator or buy something in the engine high side voltage ( plug wires etc )

BWhitmore · 2014-01-05 18:42

Jim - thanks. I think I may have just such a clip in my stash. The problem with my radio I get no radio sound at all - just static even when the engine is not running. When I test the radio off the car it works fine. I have installed dedicated ground wires for the radio and the antenna and even installed a 12 volt powered antenna - still only static. I have had this radio in and out of the car 5 times, and as you know I need to drop the under dash a/c unit (Mark IV) every time I work on the radio. I am just glad I allowed for enough flexibility in my a/c hoses so I do not have to remove the a/c hoses from the back of the under dash unit. Thanks. Bill

LAUDY57 · 2014-01-05 18:43

Have you applied an external 12v to the radio while it is in the car?

hiball3985 · 2014-01-05 19:03

Lorne has a good suggestion. If it plays on the bench ok and not in the car is could be the speaker, can you run the speaker wires to an external speaker. I'm thinking a short in the speaker could be grounding the output...

LAUDY57 · 2014-01-05 19:11

I was thinking of an independent 12v source like a power supply or battery hooked directly to the radio wires, both 12v and ground, then individually to see if clean power and/or ground to the radio would make any difference.

BWhitmore · 2014-01-05 19:16

Good suggestion. I will hook up an independent 12v source to the radio and see if this makes a difference. Thanks. Bill

BWhitmore · 2014-01-05 19:24

Is there such a thing as "polarity" in the speaker wire hook up? If the speaker wire is hooked up backwards to the speaker could this be the problem? The speaker wire has the 3 prong hook up at the radio and two slide on terminals at the speaker. When checking the radio on the bench I have used another speaker. The speaker in the car is new and I can clearly hear the static so I always assumed the speaker in the car is OK.

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hiball3985 · 2014-01-05 19:33

There is a polarity on a speaker but with the original radio that is mono it shouldn't make a difference as long as it's the correct two wires. I'm not using my original radio and speaker so I'm not sure what the three wires on the radio side are? Where does the third wire go after coming from the radio if there are only two at the speaker?

BWhitmore · 2014-01-05 19:44

I think the third prong on the radio side of the speaker wire is a positioning prong only.

BWhitmore · 2014-01-05 19:46

Both a positioning prong and also a retention prong. If I remember correctly the third prong has a "barb" on it for retention.

hiball3985 · 2014-01-05 19:53

OK that makes sense. Sorry for all the questions, but have you taken it out and bench tested it since the first time you tried it? The reason I ask is it could have worked fine at the shop but these old radios can blow capacitors at any time, like the first time you turn it on and it gets 12V.
My other thought still goes back to the speaker, even being new it could be defective.

RICH MUISE · 2014-01-05 20:02

A handy 12 v power source...even has a on/off switch, and a polarity switch

BWhitmore · 2014-01-05 20:56

Jim - I have actually bench tested the radio 3 times with the most recent test being 1 week ago. I will borrow a speaker from my neighbor and give it a try (a speaker that I know is good). Rich - good power source. I have an extra 12v car battery and some long jumper leads so that I can sit the battery on the ground (with the battery grounded to the frame) next to the open door. Thanks.

I will let you know the results.

hiball3985 · 2014-01-05 21:06

Good luck Bill, I know how frustrating it can get with something as easy as hooking up a radio goes wrong, it always seems the little things get you

This is really taking a stab in the dark but is there anyway you could have mixed up the light and power wire? Maybe the radio will play if you turn the dash lights on bright. Just kidding

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Hood Bond?