western

Voltage sensitive switch [relay]

44 posts in this topic

Do any of you know if there is a fairly easy way to test the Voltage Sensitive Switch [VSS] relay off the vehicle ?

it's the yellow one that hides in the far right corner of a 90/110 dash [PRC4427 or AMR3325]

I need to check the 2 I have, because I.m not sure if these are working properly, there is 12v feed on the brown wire & continuity on the black & black/slate wires, it's not allowing my split charge relay to operate.

found this schematic of the subject VSS.

post-20-0-71861200-1338498056_thumb.jpg

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Very easy to do if you have a variable output bench power supply, tricky if you don't. I've got one - you can post them to me and I'll test them if you like.

NIck.

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Cheers for the offer Nick, I believe the electricians at work [aircraft engineering] have a suitable variable output bench tester, I'll check tomorrow, but if my workmates can't do it, then I'll be in contact.

as for the split charge it has a different earth path now & it is charging the winch battery,but would prefer to use the VSS to control it as LR intended.

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Oi, Western. If you're going to nick stuff off my website, at least give me the credit ;)

I spent literally minutes reverse engineering that!

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Oi, Western. If you're going to nick stuff off my website, at least give me the credit ;)

I spent literally minutes reverse engineering that!

I found it via another thread on another forum, didn't realise it was yours,

Thanks very much to TSD :i-m_so_happy: for coming up with the diagram in my question above

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Now you know who drew it, you should know better than to trust it too. Get it checked by an adult is my advice :blush:

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took a printed copy to work,my workmates both a/c electricians/avionics said it was OK, we tested the VSS with a bench variable output power supply & it didn't allow any output on terminal 4 until the feed in was around 14.8 to 15 volts, so the first of my VSS is duff.

will be testing the currently fitted VSS on Weds & see what that does.

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right today, we checked the 2nd VSS part AMR3325, the unit operates on a rising voltage to 13 volts, BUT when it's in the vehicle, it's not allowing the split charge relay to operate. 2nd battery is currently at 12.08v so the system should be charging it when engine is running/driving.

I've redone a continuity test on the black/slate wires from split charge connection to the VSS socket which was all good & the brown wire at VSS socket gives me 12v also the green wire [from fusebox ign controlled] at split charge relay has 12v when tested.

next option is to replace the VSS with a new one & see what happens then, system has been working fine up until a few days ago.

don't know where or what else to check.

if split charge relay is given a different earth path it works fine but it's not controlled by the VSS.

would it be worth adding a switch in the earth path & switch it in manually when the 2nd battery needs charging. I would prefer to VSS to do it though.

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Your probably aware but just a thought, you will have continuity through one strand of wire, but it won't have much current carrying capacity. Could it be a wire chaffed partly through or corroded ?

Steve

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it's a new loom from autosparks, fitted it myself very carefully a few years ago, the VSS just won't let the split charge power up, there's one wire I haven't tested, thats a tomorrow or Saturday job when it's not blowing 60mph plus winds & rain.

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solved the fault :i-m_so_happy:

I had the 2nd battery out of the 110 for a long recharge over a weekend, must have missed :wacko: reconnecting the VSS brown 12v feed wire, traced it to battery bay & spotted it lying on the floor, so VSS had no way to determine if it should operate or not, reconnected the brown & VSS & split charge working as it should, thank god that job is finished. :i-m_so_happy:

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Yes, it's not a cheap part. but if anyone wants the system work work as designed, I don't think there's another option.

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There are a few on ebay cheaper

I know, but I would much prefer a new one.

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The circuit is very cheap and simple, and all the parts are easily available. Can't you find someone to fix your duff one?

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possibly if I knew which bit was duff & what to buy, would the 8 leg black chip need reprogramming ?

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a bit of useful info I've learnt today, the later version of the Voltage Senstive Switch is

AMR3325 -- No longer available

but the earlier version PRC4427 is still available form Brit-car.http://www.brit-car....php?xProd=89705

I happened across this one the other day -

STC61888 SWITCH RELAY LIGHTING TOMB RAIDER DEF

£54.04 (+ £10.81 VAT in EU)

http://www.brit-car....hp?xProd=103436

STC61888.jpg

I wonder how this one differs to PRC4427 and AMR3225

.

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never knew that existed till now,
to late for me as I've got the PRC4427 on it's way to me, I know this will fit & work, as it is the original unit in my '89 110.
I don't think Brit-car know it's a similar item either as they weren't aware that PRC4427 is the same as AMR325, until I asked about it.

the parts info http://www.numcat.ru...ver/p/31/53684/ item 12 says it's a switch lighting not a VSS. Very strange, wonder why it's used on the tomb radier vehicles.

Edited by western

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never that existed till now,

to late for me as I've got the PRC4427 on it's way to me, I know this will fit & work, as it is the original unit in my '89 110.

I don't think Brit-car know it's a similar item either as they weren't aware that PRC4427 is the same as AMR325, until I asked about it.

If it'll do the same job as PRC4427, it's almost a third of the price :o

the parts info http://www.numcat.ru...ver/p/31/53684/ item 12 says it's a switch lighting not a VSS. Very strange, wonder why it's used on the tomb radier vehicles.

Microcat doesn't make it too clear, but it looks as though this was fitted in the circuit for the roof lights - perhaps so that they could only be used with the engine running?

.

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Reckon I'll be speaking to Brit-car on Monday, to change my order for this STC61888 version, don't understand LR's pricing policy for some items

sent Brit-car a e.mail & I'll talk to them on monday, great spot Paul, I owe you a few.

as for use on the tomb radier, reckon your right about it being used for the extra roof lights, can't see any other reason for having 2 VSS.

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possibly if I knew which bit was duff & what to buy, would the 8 leg black chip need reprogramming ?

What I meant was if you knew someone locally who understood electronics and faultfinding, it wouldn't take long to work out what the fault is.

Apart from the time it takes to do it, you could replace every component in there for about £5. Nothing needs programming, and there's only one adjustment, which sets the trip voltage.

IIRC the same switch is used in RRC to prevent the rear screen demist from draining the battery, so there's lots of s/hand ones out there.

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mine is for rear screen heater too, but it can also switch the earth path for the split charge relay, I know it's used in various vehicles, but wsn't aware of it's use in the tomb raider, it'll have to wait now as I'm working away hor the next week..

.

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took a printed copy to work,my workmates both a/c electricians/avionics said it was OK, we tested the VSS with a bench variable output power supply & it didn't allow any output on terminal 4 until the feed in was around 14.8 to 15 volts, so the first of my VSS is duff.

will be testing the currently fitted VSS on Weds & see what that does.

If its as you describe the circuit is not "duff" - its working exactly how it should - it does however need adjusting.

Step one -

Get it back on the bench and set the bench PSU voltage to whatever voltage you want it to opperate at, then turn the pot until it switches.

Step two -

Now make sure the relay doesn't hold in if you reduce the bench PSU below 13.0V

you *may* need to adjust the pot step one and two a few times to get this to work as you want but its straight forward to do.

HTH

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