Solved: Volvo Guard 1 remote C/L range.

[Forrest]

Mine only required a very minor adjustment but I have found I have had to go back in a couple of times and tweak the blue component. On the last occasion I gave it a good turn in both directions before fine-tuning it and it seems to have been more stable. I wonder whether it has degraded over time. I'm guessing the tuning circuit is a simple LC circuit comprising the variable capacitor and coiled inductor.

I own four fobs with two in daily use. I have three of one circuit design and one which looks quite different, like xad001x0w describes in his second post. The different one seems a bit reluctant to work from a long distance but has the advantage that it lacks the flat, black two-pin component that has a tendency to break away from the circuit board. This has happened at least once to all three similar fobs.

If anyone has a broken fob that won't work/light the red LED when the button is pressed despite new batteries (correctly inserted) then check for this component inside the fob. It can be repaired using a carefully applied blob of solder.

[Forrest]

The instability I described above continued so I have today tried something more drastic. Variable capacitors of this vintage are aparently notorious for becoming unstable with age. These (Murata TZB4Z060AB10R00 2 to 6 pF) are an exact replacement for the blue component.

http://www.ebay.co.uk/itm/MURATA-TZB...-/171138420639

It is worth getting more than one. They are very small and hard to find when dropped. This link is for a pack of five.

Ideally, one should remove the trianguar receiver from the car before attempting this repair, but I did just about manage it in situ. You need a soldering iron with a fine tip to avoid damage to surrounding components. It is important to get the replacement the same way around as the original. I marked the top of the original with a felt pen before removing it then using distinctive markings on the underside to ensure the replacement was fitted the same way around.

Miraculaously, the remote is now working again. I'll report again if it lasts or not.

[James_EG_940]

Glad people are finding that this works, I apologise for never coming back and adding photos - it's been at the back of my mind for ages!

I can confirm that my fob has seen no degradation in performance since I've applied this fix - this is probably why I've never bothered to pry the little cover off and take more photos for this thread.

I agree with Forrest that if you have no luck or a stable setting cannot be found then your best bet is to replace the variable capacitor and that if you have a good soldering iron with a fine tip it should be easy enough to replace in situ. Although if you are a bit more novice with soldering then ripping all the A pillar trim off and getting access to the PCB is your only hope.

As I think I mentioned before, I also ran in an antenna extension round the entire cabin of the car, this allows me to play my favourite game: making people think they've unlocked the wrong car at Tesco. I can lock/unlock the car a good 5 or 6 times before I get to it from the front door of the shop, made someone jump once!

Cheers
-James.

[loic t5r]

I unearth the topic, because I am in France, and I have the same problem with my Volvo Guard 1 so I will do the manipulation after buying batteries for the remote control which works more for 10 years !!
I hope it will work on mine.

[TonyS9]

I also tried this and it works temporarily. I think what is happening is some temperature compensation is not working correctly and you need to keep adjusting it. Eventually the alarm died due to a low battery voltage and failed start attempt and I had to bypass it.

[Forrest]

I am pleased to report that nearly six years on my repair by replacing the Murata capacitor (post 12) is still working very nicely. The fob works from a considerable distance away and the unit has not required any subsequent adjustment.

[James_EG_940]

It will definitely be the failing adjustable capacitor as per Forrest's post earlier. I have noticed too that it varies due to temperature but with all the components being heading for 30 years old now it's not surprising. If every component in that little triangle drifts even 1% in value it will really upset the sensitivity of the receiver especially when it works at such a high frequency.

I'll try and look more closely at what's going on on that circuit board and reverse engineer it at some point but replacing the little variable cap and retuning should solve most issues for the time being!