Volvo Guard 1 Keyfobs

[James_EG_940]

Hi guys,

I have racked up a fair bit of experience with these fobs now so thought I would write an article and share it. This is a moderately long article with images, sorry to anyone on poor rural broadband!



These are the fobs used to set the alarm / remote central locking on cars with the flashing triangle on the driver's A pillar - not the later system with the blinking LED inset to the passenger side dash speaker grille.

There were some variants on this system, with some fobs having a second button to start the block heater. Other fobs worked on IR (like your TV remote) rather than radio - I have never seen one like this. To comply with different countries laws on radio emissions some work on different frequencies, this is indicated by the coloured band around the middle of the remote. As far as I know there were red, blue and black banded ones - blue is the correct colour for UK cars.

The VG1 system has issues with range, see how to fix that in another post of mine here: http://www.volvoforums.org.uk/showthread.php?t=200312 but this is largely not down to the key fob. The fob does however have its own slew of problems especially as they all are now 20 years old or older! The fobs are actually quite simple, once you remove the screw the case can easily be split apart with a finger nail - working from the short edge closest to the button around.


This allows access to the PCB for repairs, being very careful with the incredibly flimsy plastic colour ring!


Electronically there is a microcontroller which will repeatedly pulse a pre-programmed code when powered up, this is then broadcast on a 418.050MHz carrier. Due to the code being stored in the microcontroller it wouldn't be possible to reprogram with a new code without having the original computer code used to program the chip.

There seem to be a couple of circuit board variations, an older one and a newer one. I'm not sure how many years they were produced for but I have two "older" boards with a date code of 45th week 1994, another "older" one with 50th week 1995 and then a "newer" board with no date code. I think it's newer judging by the components used. They are functionally identical and both types can be simultaneously used with 1 car.


The main problems with fobs I have come across are: Battery leak corrosion, broken battery cover, failed switch, dead LED and dead batteries

Battery leak corrosion
These get left for decades with dead batteries in them which then leak and start to eat up the tracks of the PCB inside the fob. This can be cleaned up with alcohol and joints reflowed, if a track is completely gone it can usually be repaired with a jumper wire. Most problematic around the negative battery terminal which will already be electrolytically corroded.



Broken battery cover
A bit of terrible design here I'm afraid, the fobs take 4(!) cells, these are fitted into the fob in 2 pairs and arranged electrically as all 4 cells in series. to bridge the 2 pairs together a small spring strip is used which is a press fit onto a screw post on the back of the black plastic strip of the fob. The problem is that this tiny screw post becomes brittle, cracks apart from the tiny self tapper holding it in - this in turn means the battery essentially becomes disconnected! I have yet to get a good fix for this, araldite may be one fix, but there isn't much space to allow for the inevitable epoxy that squeezes out when you fit the parts together. Another option I have been considering is to make a highly accurate 3D model of the part and get a whole bunch of them 3D printed...



Failed switch
The tiny tack (tactile) switch on the fob wears out so that you have to press really hard for it to make contact which then breaks it further. Tactile switches do break quite easily and have a short service life - I've repaired a lot of DJ gear with faulty "attack" switches as we call them (attacked by DJs smashing at them). Repair is to simply replace the faulty switch. This can be one of the main reasons people say their fob doesn't work, it's the most common "I've changed the batteries but it still doesn't work" issue. I use these switches when replacing them: switch link


Dead LED
I have come across two fobs with dead LEDs so now I just replace them as standard. The ones on there are usually all faded and not exactly bright anyway. I couldn't source exact copies of the ones on the board so I use slightly longer ones and clip them down which works well. Would be very easy to change the LED colour too.



Dead Batteries
As I said earlier there is a little screw on the back, that releases the black plastic part on the front which retains the batteries. Polarity is important is not marked anywhere on the unit. The negative terminal is furthest from the switch, positive closest. Due to the two stacks though you will need to place them so that positive faces up out of the negative hole (ie negative side facing down to the PCB) and vice versa for the positive hole. Each fob uses 4x 1.5V watch batteries with the code: 391 or L1121 or any of the other synonyms for that type of cell. Use only genuine quality branded batteries to avoid leaks, I recommend Varta or Renata. Be very careful not to over tighten the screw when you replace it as once the little screw post splits (which it will!) it's game over. Amazon link for batteries



So that's about it. Apart from those things I mention above, they are fairly bullet-proof little units and should last a while. I'm all for trying to keep things stock and keeping some of the stock 90s electrics going is not always easy. Hopefully this is useful to the few of you that still have cars with this alarm system fitted. If it all seems like too much to repair your fob yourself then I would be more than happy to repair it for you, just PM me if you are interested - I will get an alert sent to my email address.

[jpliddy]

hi amazing bit of info on the grey fobs i have still got 2 working and 1 not working
they should last as long as the car hopefully

[Clan]

You forgot the most common fault i found with these over 20 years , a little capacitor falls off and rattles around inside , easily soldered back on it's pads with a fine soldering tip

[TonyS9]

I've been using mine with nut and bolt through it for years, maybe its time to 3d print a new one. You can just go onto Tinkercad and design one up and print directly to a print service for a few pounds(this would be about GBP5 for one off). Took me a hour to learn it, then a few hours design the thing I wanted. The problem is with this is there maybe a 'shelf' for the tab, you can only reliably print off vertically to about 45 degrees, still you can just cut them down after adding supports.

[Forrest]

I have managed to collect five fobs and have one car with the guard 1 alarm so it wasn't a disaster when my glue repair to the battery cover gave up. I just swapped it with a sound one. The repair I contemplated, but never tried, was to glue a deep metal nut in place of the plastic post and use a small machine screw instead of the self-tapper.

It would be worth linking this thread with the ones about repairing the triangular receiver.

Good work. Thanks for taking the time to write this up.

[MWCheshire]

This post is very helpful as I've recently bought a 1995 940 2.3 Estate which is in lovely original condition. My car has 2 Volvo Guard 1 keyfobs - 1 of which works and 1 of which doesn't...

I haven't approached Volvo directly yet, is it still even possible to get a new keyfob for this system?

Failing that, do you still repair them and what does it cost etc?

Many thanks.

(I tried to send a PM but as I've only just joined the forum, it wouldn't let me...)

[TonyS9]

I would expect there aren't any spare parts like that from Volvo.

The main units give up eventually, but you can fit an after market unit with a little wire knitting.

[James_EG_940]

Hello all,

Mark - as Tony says I highly doubt Volvo will have any spares at this point. VG1 was only fitted up to the model changeover in 1994/1995 and after that they moved to the VG2 system which is a fair bit easier to find the fobs for. The fobs are a bit like hens teeth now although some of us on here have hoarded them somewhat! I'd be happy to take a look at yours if you want but do try changing the batteries first and "re-syncing" it to the car with the guide (PDF) that I've posted on here a few times as well - the guide also includes methods to change the light flashes and horn beeps when you lock/unlock etc among other things.

As a general update to this post, I'm in the process of looking into getting the black plastic cover part 3D printed as it's exactly the type of thing that suits 3D printing. If people are interested I could maybe get a few made and sell them on for cost+postage.

Not sure if it's worth moving this thread to the "Articles" section mods?

Cheers,
James.

[Forrest]

Just to add to the advice above to make sure the four batteries are inserted correctly. One stack of two button cells is the opposite way up to the other pair. Check your working unit for the correct orientation.

Also check for corrosion due to old cells leaking. In my experience the easiest way to clean the contacts is to dismantle and remove the pcb then carefully use a dremel on a fairly low speed with a brass brush attachment.

Given all the basics are right the most common fault I’ve encountered is the legs on the Murata ceramic resonator breaking. See picture for help identifying this part. Either resolder or desolder and replace depending on the extent of the damage. The component is a few pounds on eBay.

[jpliddy]

thanks JAMES for this post its very good . i programed a spare fob a few years back all was ok then i had a starting problem which is very rare in the 19 years ive had the car a knowlageable chap who knows a lot about this car/model told me to remove the fuse for the alarm which i did and the car was ok again .after a while i replaced the fuse and alarm all ok but ive not used the spare fob so only 1 original fob programmed in to car .
are you familiar with faulty tempreture gauge my car is a 940 diesel tdi
regards jim