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Voltage sensitive switch [relay]


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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

Cheers for the info,I'll give it a try next week, when back home.

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  • 4 weeks later...

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.

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.

I have a Tomb Raider Defender and yes the STC 16888 is for the roof mounted lights. What is this part, whats its function and how does it work? How can I check if mine is faulty... in simple terms please.... My electrician says its bad so he bypassed it but I'm sure he doesn't know what it is and how to check it. Now all of my lights are weak the top ones as well as the headlights I'm not sure if this happened as a result of removing the VSS or for some other reason since I can't recall the time. Is there a seperate VSS for the headlights too?

Thanks!

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as in GW91ZR's reply a bit up the page, you'll need a 12volt variable output supply, & a mulitmeter set to DC Volts

terminal 2 on the VSS is earth/ground

terminal 3 is 12 v supply in

terminal 4 is output to the load [lights/rear screen heater]

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as in GW91ZR's reply a bit up the page, you'll need a 12volt variable output supply, & a mulitmeter set to DC Volts

terminal 2 on the VSS is earth/ground

terminal 3 is 12 v supply in

terminal 4 is output to the load [lights/rear screen heater]

Got it! So even if this is faulty and I leave every thing the way it is (bypassed)... The down side would only be that the top lights would work with the engine off...right? But why are all the lights weak?? They don't have enough juice in them... the way they used to be?!

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Got it! So even if this is faulty and I leave every thing the way it is (bypassed)... The down side would only be that the top lights would work with the engine off...right? But why are all the lights weak?? They don't have enough juice in them... the way they used to be?!

Assuming its been bypassed correctly that would be the only downside. I'm assuming that whoever bypassed the VSS left all of the original wiring and just bypassed the VSS. If so then it is probably a poor earth as Western has said. However if the bypasser actually rewired the whole lighting theres a chance that poor quality/insufficient guage wire was used but this wouldn't really explain why they were once bright and know not so much. Bad earths are the cause of so many quirks.

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I'd be a little worried here that the person who bypassed the "relay" might have just used the switch supply to feed the lamp, the smaller wire used to control the relay could have large voltage drop and you could damage the switch, time to get the meter out and work out exactly whats been done.

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  • 1 month later...

I'd be a little worried here that the person who bypassed the "relay" might have just used the switch supply to feed the lamp, the smaller wire used to control the relay could have large voltage drop and you could damage the switch, time to get the meter out and work out exactly whats been done.

The person bypassed it by connecting the terminal 3 and terminal 4 for the switch, together... Everything else is original.

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I've been talking to a company who make high current relays. They also sell a VSS rated at 200A - which strikes me as useful for Split Charge applications in this market as well as a host of other demanding stuff that the Land Rover VSS is just not up to.

Even if I buy them in decent quantities, they would have to retail for about £80. Do you think this would represent good value? On one hand it seems a lot, but on the other, most VSS's seem to cost that sort of money - but only switch 10A to 80A. I don't know?

Si

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Hi gents, interesting reading. Slightly off topic but......I've been scratching my head a lot on how to wire up a warning light when I switch off the electric cooling fans ( for deep river crossings.....V8) I have removed original engine driven fan. Then was reading through this post and a very small light came on..........could I use a VSS to switch on the warning light or is the a much better cheaper way? I probably have a couple of them sitting around as It now has a soft top, no rear window heater and a broken disco in my yard. Any advice might stop my scratch. Thanks.

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Hi gents, interesting reading. Slightly off topic but......I've been scratching my head a lot on how to wire up a warning light when I switch off the electric cooling fans ( for deep river crossings.....V8) I have removed original engine driven fan. Then was reading through this post and a very small light came on..........could I use a VSS to switch on the warning light or is the a much better cheaper way? I probably have a couple of them sitting around as It now has a soft top, no rear window heater and a broken disco in my yard. Any advice might stop my scratch. Thanks.

Depends how it's wired, but usually a small warning lamp (like one of the dashboard ones) can be wired just across the switch or relay terminals (whichever switches the high current). When the switch is closed, everything operates normally and the fans run if they need to. When the switch is open, if the fan 'stat switches on, the warning light pulls a small current through the fan motors, and illuminates. (This is just the same trick used to make a blown fuse indicator). The only downside is the light only comes on if the fans try to run, not just when the switch is off.

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Thanks for info, that hadn't even entered my mind. I have a kenlowe fan and its thermo controlling unit ( for lack of a better discription) so was going to wire the pos feed to an on off switch. Would running a wire between the terminals to a warning light still work? And why wouldn't the warning light illuminate when switch is on? Path of least resistance? Maybe even connect this pos power lead to a VSS so it only comes on when the engine is running and not on the key. Cheers

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  • 6 months later...

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