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Radio fuse keeps blowing (#7)

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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Radio fuse keeps blowing (#7)

Post by elchopperfreak » Fri Dec 16, 2011 10:20 am

Hi guys
First and foremost Happy Holidays to all
Been quite busy, so have not been around much.
My 99s 70 T5 lost all power to radio, I checked fuse 7 (I believe) and alas was blown, replaced the fuse and it blew right away.
I disconnected the radio wiring, amp, power, speakers, etc, in short radio out, placed another fuse and it blew again right away.

Did a quick search but no real answers to the problem. My guess is a short, or maybe some trickery under the fuse box, before I start witch hunting down the culprit, any clues or hints on what to look for?

This happened out of the blue, although my wife tells me a couple times the radio went into code in the past weeks, and last saturday the car had not power which I solved by giving a shimmy to the battery cables althought they seemed tight to me

Thanks in advance for the help

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Re: Radio fuse keeps blowing (#7)

Post by fazool » Fri Dec 16, 2011 10:47 am

I would assume it must be a short. If it were a stuck relay that would simply deliver power when on, etc. If the radio went into CODE previously, it lost power. All things point to a short in the cable feeding power to the radio itself.

The only like locations for such are where they go through metal openings or rub against a metal edge.

Sometimes a wire can pull out of a connector and flop around but that would cause loss of power always.

I just looked over the wiring diagram here in the MVS repair databaase. Fuse 7 feeds a red/black wire to connector pin 10 of the 53-pin instrument panel engine compartment connector #24/13

This then branches out from there to TWO red/black wires which BOTH feed the radio. Dunno why there are two.

Here is a very very simple test for you to do.

Pull the radio out and unplug the connector on back. Run a simple continuity check from the two red/black wires to ground. One of them is likely shorting.

Do this with power off. If it doesn't short then, turn your power on and try it again. This will help determin if it is upstream of the relay and switches.
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2007 S60 2.5T AWD (Daily Driver)
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Re: Radio fuse keeps blowing (#7)

Post by Volvo Manic » Wed Jul 29, 2015 12:08 pm

My problem with fuse 7 just started. My radio pins all test correctly, do not seem to be shorting out.
Even with the radio control head disconnected my fuse blows immediately. There is a strong spark that jumps out as the fuse touches the contacts, instantly blowing the fuse well before being seated.

I need to disconnect my aux CD changer next. Does anyone have other ideas or seen this fuse 7 type problem before that is not in the radio control head?

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Re: Radio fuse keeps blowing (#7)

Post by precopster » Wed Jul 29, 2015 12:31 pm

In my 98 V70R it wasn't the radio blowing the fuse as it still blew without it being plugged in. I have the SC900. The connector going to this radio has 2 green/red wires for power. One is going to the radio and the other is connected directly to it and feeds the amp circuit.

Next on the list is the under seat amp; scarce and expensive.
Current cars:2002 XC70, 2006 Ssangyong Rodius (Stavic), 2006 XC90 2.5T, VW Transporter 2.5TDI


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