Radio/Stereo: V70 SC900 intermittent FM signal

[Clan]

Originally Posted by Luxobarge

OK, so I had some time to look at this again today. I've had all the interior trim out at the back of the car, and on the right side (driver's side) I cannot for the life of me see anything that could be a bumper antenna, no wires at all go through the rear of the car at the bottom, or anywhere near it, no antenna amplifier, no co-ax cable, nothing. So while I still stand to be corrected, it very much looks as if my car doesn't have an antenna in the rear bumper. If you still think it does, can you tell me exactly where to find evidence of it, i.e. where the wires are, where the amplifier is? Cheers!

So while in there I spent some more time investigating the antenna in the window on the left side. I tuned to a weak station and it got weaker when I pulled the antenna connectors off, and weaker still when I pulled the co-ax cable out of the amplifier, so that's all as it should be. However at no point could I replicate the problem of suddenly losing all sound. It's very frustrating that the problem is so intermittent, as we all know it's very difficult to diagnose a problem when the symptom isn't present!

I did find that the torx screw holding the antenna amplifier to the car body was loose, so tightened that up of course.

Only thing to note is that the fault is often there when I first turn on the ignition. Today this happened, once the radio has come on and the display is on, sound should come almost immediately, but today it didn't. I thumped the side of the console with the heel of my hand and it started working. This has all the hallmarks of a dodgy connection somewhere in the central console area, so after I'd finished at the rear of the car I slid the radio back out and had a thorough fiddle around with all the cable connectors and harnesses near the radio, and found absolutely nothing - the radio was playing just fine the whole time. If I'd got anywhere near the fault I'd have expected it to lose sound at least for a moment, but it seemed as solid as a rock.

Still perplexed by this one, we'll see how it goes when I next drive the car around, but I'm not confident that the loose antenna mounting screw will have fixed it - we'll see. I'll update again either way.

Cheers!

Odd that you do not have the "diversity" antenna system .. has the SC900 got two aerial connections side by side in the same plug? Maybe that was for the SC901 , i cant remember .

When you hit the side panel and the radio came alive , that is very unlikely to be a connection , Volvo multiplugs of that era have generous pins and robust connector blocks , Much more likely in my experience are cracked solder joints on the main board of the radio ...you have probably noticed how hot these units run and time takes it's toll. which could account for your other problem too .

[Luxobarge]

Originally Posted by Clan

Odd that you do not have the "diversity" antenna system .. has the SC900 got two aerial connections side by side in the same plug? Maybe that was for the SC901 , i cant remember .

When you hit the side panel and the radio came alive , that is very unlikely to be a connection , Volvo multiplugs of that era have generous pins and robust connector blocks , Much more likely in my experience are cracked solder joints on the main board of the radio ...you have probably noticed how hot these units run and time takes it's toll. which could account for your other problem too .

Nope, on the SC900 there's just the one co-ax socket.

Understand what you're saying about the multiplugs, and I'd agree. Also agree that it's more likely to be a dry joint somewhere, but I very much doubt that it's in the main radio unit as I replaced the whole unit for a second hand one I bought, and surely the chances of them both having the same fault are tiny?

So, let's assume it's a dry joint in the vicinity of the centre console, but where could that be?

By way of update, I just went out in the car and after stopping at the shops when I started again I got the fault - Radio display on but silence. I turned the volume right up and there was some crackling and buzzing like radio interference, so definitely an antenna-related fault IMHO. I thumped the centre console again and got sound for a moment, then silence again. Half way back home it came on again all by itself, and stayed on until I got home - also typical of a dry joint type fault I reckon.

This is really driving me mad, however thanks for the help so far, any more bright ideas are very welcome!

[Clan]

Originally Posted by Luxobarge

Nope, on the SC900 there's just the one co-ax socket.

Understand what you're saying about the multiplugs, and I'd agree. Also agree that it's more likely to be a dry joint somewhere, but I very much doubt that it's in the main radio unit as I replaced the whole unit for a second hand one I bought, and surely the chances of them both having the same fault are tiny?

So, let's assume it's a dry joint in the vicinity of the centre console, but where could that be?

By way of update, I just went out in the car and after stopping at the shops when I started again I got the fault - Radio display on but silence. I turned the volume right up and there was some crackling and buzzing like radio interference, so definitely an antenna-related fault IMHO. I thumped the centre console again and got sound for a moment, then silence again. Half way back home it came on again all by itself, and stayed on until I got home - also typical of a dry joint type fault I reckon.

This is really driving me mad, however thanks for the help so far, any more bright ideas are very welcome!

Don't be fooled , these units are getting on now it is 20+ years since they were introduced and most of the cars they were in have done 200,000 miles , that is a heck of a lot of heating and cooling cycles twice a day , which is what causes cracked solder joints , also if they were using unleaded solder that is another cause .

[greenz]

Originally Posted by Luxobarge

Nope, on the SC900 there's just the one co-ax socket.

Understand what you're saying about the multiplugs, and I'd agree. Also agree that it's more likely to be a dry joint somewhere, but I very much doubt that it's in the main radio unit as I replaced the whole unit for a second hand one I bought, and surely the chances of them both having the same fault are tiny?

So, let's assume it's a dry joint in the vicinity of the centre console, but where could that be?

By way of update, I just went out in the car and after stopping at the shops when I started again I got the fault - Radio display on but silence. I turned the volume right up and there was some crackling and buzzing like radio interference, so definitely an antenna-related fault IMHO. I thumped the centre console again and got sound for a moment, then silence again. Half way back home it came on again all by itself, and stayed on until I got home - also typical of a dry joint type fault I reckon.

This is really driving me mad, however thanks for the help so far, any more bright ideas are very welcome!

did you figure out what it was yet? having same problems in 06 xc70. intermittent comes in an out when it wants to.

[Luxobarge]

Yes I did get it permanently sorted. Turns out that it was dry solder joints on part of the circuit board inside the radio where the FM tuner circuitry is. I found an excellent radio repair shop in Brighton who repaired it for me, reasonably cheaply too.

I was initially VERY reluctant to believe that it was anything inside the radio unit, as I had procured a supposedly good working unit from another member on here (who shall remain nameless) but the exact same fault remained, so I thought I had eliminated anything inside the unit. However, it turns out that this is a relatively common fault and the replacement unit was indeed faulty in exactly the same way. So once the shop had repaired my unit, I swapped them over and got them to repair the other one too, so now I have a good working spare unit. The shop confirmed that the second unit had faulty solder joints in exactly the same place!

I'd be surprised if it was exactly the same fault in an 06 XC70 unless it has the same radio unit? It's perfectly possible though, so I hope this helps.

The above fix was a few years ago, and it's been going perfectly ever since, I have the radio on all the time when driving, and very good it is too.