Home page

C4 Electrical

Erratic FM/AM reception in Bose radio (1/6)
 7/26/18 10:37pm
raymnz
Standard Member
Send Private Message

, - New Zealand

Vette(s):
White 1988


Joined: 2/1/2017
Posts: 11

I have a 1988 C4 with a factory Bose Delco radio that has intermittent problems with the radio reception. The cassette works fine. At some stage an Alpine CD changer (in the luggage tray behind the passenger seat), control unit (dash mounted) and FM modulator (behind the radio) has been installed. When the Corvette gods are smiling everything works just fine - CD OK, cassette OK, both FM and AM radio reception fine. Then something like Schroedinger's Cat kicks in and the radio stops - a both dead and alive situation. This can happen when: the car goes around a corner; the shifter is moved; the car is accelerated hard; the Nile River is in flood...you get the picture. On some occasions, things will work again when the side of the radio housing is given a good bash. Sometimes again, when the trim is gently pushed. Sometimes this has no effect at all and the radio will suddenly burst happily into life for no apparent reason. Oh...BTW, when I say the radio is not going it does give the 'off station' hiss - as loud as the volume is turned up!

Delving in the innards behind the radio I found not one but two FM modulators - one made by Alpine for the CD changer, the other something else. I have checked all the connections - all seems OK.

My question is: can a faulty relay cause these problems? There is always power to the radio, its just the reception. The antenna is OK - besides the CD doesn't route through the antenna though the FM signal from the controller and changer and the antenna both go into the modulator. The symptoms would indicate something loose somewhere or possibly the relay, though I would think that the radio would be totally dead if the relay was sticking (??). Any ideas of how to sort this out would be appreciated ... I have spent a year trying to get to the bottom of it.


______________
Our Sponsors help support C4VR
Sponsor Ad

Re: Erratic FM/AM reception in Bose radio (2/6)
 7/31/18 11:57am
Atchafalaya
Standard Member
Moderator
Send Private Message

Atchafalaya Basin, LA - USA

Vette(s):
Black 1979 L-82 Black 1996 LT1 Black 1999 Coupe


Joined: 3/20/2009
Posts: 518

In a 30 y/o vehicle I always look for proper grounding first.
 
Then I look for pinched wires, internally broken wires, continuity in wires and connections, etc...
 
Those are free to check on any type of electrical problem.
 
Once I can establish the fact that electrical wires and connections are in tact; that's when I look for component failures.
 
GL
Re: Erratic FM/AM reception in Bose radio (3/6)
 8/1/18 3:35am
raymnz
Standard Member
Send Private Message

, - New Zealand

Vette(s):
White 1988


Joined: 2/1/2017
Posts: 11

Strats-N-Vettes said: In a 30 y/o vehicle I always look for proper grounding first.
 
Then I look for pinched wires, internally broken wires, continuity in wires and connections, etc...
 
Those are free to check on any type of electrical problem.
 
Once I can establish the fact that electrical wires and connections are in tact; that's when I look for component failures.
 
GL

Thanks for those suggestions. I pulled the radio out (again!) and had a fiddle around in the back of it. Yep...sure enough there was intermittent cut out, so yes, a dodgy connection. Put the thing together again, very carefully, once I had it going and so far it's kept working.

I think there is a power connection somewhere from a radio connection to the CD controller as that cut out when I jiggled the wires around. As you no doubt know its a nightmare back of the radio - if the problem rearises I'll get onto it with a multimeter.  As you say it could well be an internally broken wire. To further cloud the issue there has been the addition of a) a manual switch for the antenna and b) a manual switch for the cooling fan, both operated by toggle on the dash. I suspect that one or both of these draws power from the radio electrics.








______________
Re: Erratic FM/AM reception in Bose radio (4/6)
 8/2/18 11:18am
Atchafalaya
Standard Member
Moderator
Send Private Message

Atchafalaya Basin, LA - USA

Vette(s):
Black 1979 L-82 Black 1996 LT1 Black 1999 Coupe


Joined: 3/20/2009
Posts: 518

>>["the CD controller as that cut out when I jiggled the wires around."]
 
 
You are on to something.
 
Bad wires, loose clips/connections cause so many problems and are over-looked often.
Some shops rely on this to charge people $$$ for simple fixes.
 
30 y/o clips and connections fail, corrode, or the plastic "snaps" that hold them tight also fails.
 
 
>>[" To further cloud the issue there has been the addition of a) a manual switch for the antenna and b) a manual switch for the cooling fan, both operated by toggle on the dash."]
 
Be sure these components have their own dedicated power source.
 
Re: Erratic FM/AM reception in Bose radio (5/6)
 8/3/18 1:36am
raymnz
Standard Member
Send Private Message

, - New Zealand

Vette(s):
White 1988


Joined: 2/1/2017
Posts: 11

Strats-N-Vettes said: >>["the CD controller as that cut out when I jiggled the wires around."]
 
 
You are on to something.
 
Bad wires, loose clips/connections cause so many problems and are over-looked often.
Some shops rely on this to charge people $$$ for simple fixes.
 
30 y/o clips and connections fail, corrode, or the plastic "snaps" that hold them tight also fails.
 
 
>>[" To further cloud the issue there has been the addition of a) a manual switch for the antenna and b) a manual switch for the cooling fan, both operated by toggle on the dash."]
 
Be sure these components have their own dedicated power source.
 

At least the radio (original!) seems ok. So far, going well ... but intermittent issues crop up apparently randomly so next time the thing plays up I'll get systematic with the multimeter.  I think intermittent problems are harder to diagnose than nothing at all!

The great thing about owning a Corvette is the raft of knowledge available and the helpfulness of members of forums like this.  Thumbs Up



______________
Re: Erratic FM/AM reception in Bose radio (6/6)
 8/6/18 10:41am
Tommy Fa
Standard Member
Send Private Message

Rochester, NY - USA

Vette(s):
1984 Coupe, white w/ lipstick red interior


Joined: 6/5/2018
Posts: 1

Had a similar problem with mine.  Checked connections, pulled it out 3 times etc. Got tired of trying again and again so I purchased a 1 1/2 din radio from retro sound and replaced it. Instead of a cassette player, in its spot is a usb and an Mp3 jack. Also can pair the phone to the radio. Love it!