1991 Spider radio wiring - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 8 (permalink) Old 01-10-2017, 12:07 PM Thread Starter
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1991 Spider radio wiring

I'm replacing the non-working radio in my 91 Spider. There is no voltage in the terminal that feeds the radio itself.

Apparently, the fused relay in the circuit isn't working even though the fuse is intact. I'm guessing the purpose of the fused relay is to protect the power antenna motor since older Spiders don't have the relay. I don't have a motorized antenna nor do I want to install one.

The replacement radio is protected by its own 10amp fuse.

Is it OK to bypass the relay or would it be better to replace it?
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post #2 of 8 (permalink) Old 01-10-2017, 12:43 PM
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So if you're going by the wiring diagram, it's very likely that it's wrong. The diagram shows a fused relay, but in my '91 the relay is there but non-functional (in fact, there are missing terminals for it in the fusebox!) The radio is instead powered by a retrofitted wire with inline fuse that goes to the cigarette lighter wire under the central console.

See this thread, specifically post #14 and on:

http://www.alfabb.com/bb/forums/spid...dio-relay.html

My suspicion on this is that there was an issue with the wiring harness for these cars, and Alfa fixed it by retrofitting the additional power wire. You can pull the relay and see if the fusebox terminals are missing as a quick check.

Tom

1963 Giulia Spider (1750 engine)
1974 GTV
1991 Spider
Former: 1987 Milano Gold
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post #3 of 8 (permalink) Old 01-12-2017, 04:11 PM Thread Starter
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Thanks, Tom. I'll take a look behind the console. My car is an automatic, so it's very easy to do so.
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post #4 of 8 (permalink) Old 01-12-2017, 05:17 PM
But Mad North-Northwest
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You can also just pull the "radio" relay at the fusebox. If it's like mine, at least two of the terminals it's supposed to plug into will be missing.

Tom

1963 Giulia Spider (1750 engine)
1974 GTV
1991 Spider
Former: 1987 Milano Gold
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post #5 of 8 (permalink) Old 01-14-2017, 11:44 AM Thread Starter
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Tom: Thanks again.

I’m confused about the original post and the two different wiring diagrams presented. From my car, here are the findings. First at the relay:

1. There is constant power at the connector of post 87.
2. The connector of post 30 is continuous with ground.
3. The connector of post 85 is continuous with connector 6 at the radio. This is a 1mm red/blue wire.
4. The fuse, which protects the circuit between post 30 and posts 87 and 87a is intact.
5. The circuit between posts 30 and 87 and 87a is continuous when I manually close the points but open when I do not close them.

This conforms to the revised wiring diagram included in the original post.

At the radio, the stock harness conforms to the wiring diagram in the original post:

1. Black wire to ground.
2. Open
3. Blue-yellow wire to antenna (presumably since my continuity tester isn’t long enough to test the circuit).
4. Black-white wire to a junction box (black-white wires are generally associated with dash lighting, right?).
5. Red wire coming from fuse 5 and red-black wire to the antenna (again presumably).
6. Blue-red wire to post 85 of the relay.

Modern car radios generally have constant power to preserve their memory and switched power to allow the radio to play when the ignition is on. I’m sure this applies to my car.

Unfortunately, there is no power at the terminals for 5 or 6. As I understand the diagram, one of these terminals should have constant power and the other switched power. If the relay contributes to the operation the red wire at terminal 5 should be hot and the blue-red wire at terminal 6 should be switched.

I guess the trick is to find the open circuits. It will have to wait until another day.
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post #6 of 8 (permalink) Old 01-14-2017, 12:45 PM
But Mad North-Northwest
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Yeah, see, that's messed up. On a Bosch relay, 30 is supposed to be +12v input and 87 is output to the device. If you have 12v on 87 and ground at 30 it'll cause a dead short if the relay coil is triggered. Like I said, I think Alfa screwed up the wiring.

Did you trace the wires behind the radio? On mine there is a separate wire (outside of the plastic harness plug) that provides switched power to the radio. It has an inline filter holder for a glass fuse. That's where the power comes from: the relay does literallly nothing.

Constant power on the red wire should be working, so not sure what to tell you there.

I'm on the road and don't have my wiring diagrams. See what else you can ding out and report back. You know Alfa: it's possible your car is different from mine!

Tom

1963 Giulia Spider (1750 engine)
1974 GTV
1991 Spider
Former: 1987 Milano Gold
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post #7 of 8 (permalink) Old 01-14-2017, 04:16 PM Thread Starter
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Thanks. Let me go back a step. Several years ago, I had a new Kenwood radio installed professionally. The guy who did the installation did not modify the power harness wiring on the car side, but he cut the wires on the radio side and correctly spliced them to the Kenwood harness. The radio worked for five years then suddenly died in mid December.

I purchased a newer Kenwood that has the same wiring harness as the old one thinking that installation would be straight forward. I popped the Kenwood modified harness into the stock power connector, but nothing happened. I then checked for power at the stock connector and there was none at any of the five terminals whether the ignition was on or off.

My repair manual has the revised wiring diagram, which I believe is correct. The original diagram would make the relay switch off power to the radio whenever the ignition is turned on. This defies even Alfa logic and would probably blow the fuse by pumping current from fuse five to ground.

After a few hours of fiddling around, I'm still without power to the radio harness. The red and red-black wires in the harness is continuous with fuse 5. The black wires in the harness are continuous with ground. Given that, it really doesn't make any sense that there is no power coming trough the harness. This is a mystery waiting for solution.

Ken
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post #8 of 8 (permalink) Old 01-20-2017, 07:32 PM Thread Starter
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Tom: I want to put a wrap on the issues we've been discussing about S4 radios. I'd forgotten about a spare fuse box I removed from my parts car. By inspecting it, I can provide guidance about the radio relay and radio wiring.

First, the relay. It is a standard Bosch-type fused relay as depicted in the modified wiring diagram on page 40-17 of the service manual. With the ignition turned on, the circuit between posts 85 (12v) and 86 (ground) is activated. This closes the points between posts 30 and 87 so that switched 12v current flows to the radio from the blue-red wire on 87.

There is another error in the S4 wiring diagram. It incorrectly shows fuse 5 as the source of continuous 12v current to the radio both in the diagram and description of fuses on page 40-21. However, the red wire from fuse 5 connects only to the hazard light/turn indicator relay.

In fact, the radio gets its standby power from fuse 4, which is also part of the constant power buss. The medium gauge red wire on this fuse is connected to the radio harness.

My problem was that fuse 4 had blown, presumably from a short that developed when the old Kenwood went kaput. I'll install the new one tomorrow so my wife can enjoy her music.
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