No power to Voltage Sensitive Relay (Rear Heated Window)

[damanic]

I want to use the yellow voltage sensitive relay (VSR) as a trigger for an auxiliary relay, bit I have zero volts coming in on the brown battery wire to the VSR .

I have tested the VSR on the workbench, it works, but the relay plug behind the dash is not feeding it any voltage to detect.

Looking at the wiring diagram the brown battery wire to VSR should be connected to the starter solenoid via a plug. But where is the plug?

I have followed the brown wire as far as I can, it appears to roll into a large loom that goes through the bulkhead. But its hard to tell.

Does anyone know where I can find this plug?  I figure it must have been disconnected.

I have found the three prong plug in the engine bay that is used for split charge (black-slate: vsr trigger / brown: bat+ / green*: ign+). It is not connected to anything , I suspect this is normal.  I do not have 12volts on the brown wire here either.  The brown/black-slate wires have continuity to the VSR.

Below is a diagram of the circuit highlighting the plug I cannot find. Any ideas on how to restore power to the VSR appreciated.

 

 

 

 

 

 

Edited December 28, 2018 by damanic

[damanic]

OK so I found a better diagram. It looks like the feed for the VSR comes in off the three pin plug in the engine bay. I thought this plug was just a take off for the factory split charge set up, but it looks like it needs to be hooked up for the VSR and rear demister to work.  My Landy came from factory with a rear demister, so it looks like I am missing some wiring.

So for those with a rear demister set up but no split charge system, how is the three pin plug hooked up? I'm trying to determine the factory method. Did they push a single bullet plug onto the brown 12v+ pin and run the wire to starter solenoid?  Any one have a photo by any chance?

I have added a pic of the wiring diagram, and my connector in the wind.

 

 

 

 

Edited December 28, 2018 by damanic

[miketomcat]

This may or may not help but I use a lr vsr (re set to a better voltage) to switch a solenoid for which battery charging. It's wired on the neg side of the solenoid. The switching wires go between solenoid neg and body earth. The sense wire is connected to the engine battery side of the solenoid. 

Mike

[Tim2809]

when you test for power do you have the engine running and heated rear window switched on? 

also you will still need dash lights plugged in to energise the alternator

[damanic]

Good to hear its working for you Mike. I am doing something similar, switching an auxiliary circuit between batteries depending on alternator output.

Tim: I'm pretty sure I don't need the heated rear window switched on. The VSR is used as a negative trigger for the rear demister relay, apart from that it simply detects battery voltage and opens a path to ground when volts are over ~13.5.  Regardless of alternator on or off, I have zero volts arriving at the VSR. This is a brown wire feed, which should be unfused direct to battery. So I am missing a connection somewhere.

I guess I will wire the brown pin on the three port plug (pictured above) to the starter solonoid and that will be that.  At least that's what the circuit diagram is pointing me towards. I'm still  curious to know how that three pin plug (pictured above) was hooked up at the factory. The way I am reading it, there must have had a 12v feed plugged into it for the rear demister to work.

[western]

The 3 pin connector is only for the factory fit split charge unit, I have it fitted to my 110, the vsr is to prevent power being drained from batt. when rear screen heater is switched on without engine running, 

[damanic]

That's what I thought western, so the brown wire 12v feed to the VSR comes from somewhere else and not via the three pin plug on bulkhead?  Any idea where I can look for the  loose connection?

Edited December 28, 2018 by damanic

[western]

mine comes out of the dash/main loom near the heater unit, the other end is within the loom behind the dash & goes to the VSR, without pulling the dash out its difficult to say for definite.

 

the connector in your first diagram is just a code for a inline conector. 

[miketomcat]

The lr vsr turns off at about 11.2v unless you adjust it. Mine is set around 11.8 cut off which cuts in at about 12.7 so if you have lights, heater etc on it doesn't cut in (my alternator is getting tired I think) but when there's little load it cuts in and charges but cuts out about 3 mins after I stop the engine.

Mike

[damanic]

If the brown wire to VSR is plugged into the loom somewhere behind the dash, I cant find it.  The only brown wire connector I can find that has continuity to the VSR is the split charge plug on the bulkhead. So I guess its easier to just hook that up to the starter solenoid seeing as its hovering just above it.  If I do that I should get a good reading at the VSR, with barely any voltage drop. 

I have a 120amp alternator with upgraded wiring. My on dash volt meter reads steady at around 14v even when the 40amp electric fans start up. So the VSR should be good for my intended use.

Apart from its usual rear demister duties the VSR will be switching an auxiliary circuit onto the starter battery when the alternator is running, and back onto the aux battery when the engine is off. The aux battery is charged via DCDC+Solar which has a limited amount of charging amps, so to maximise charge speed all loads are switched onto the starter battery / alternator when engine running, so that the aux battery can use all the given amps for charging.  There are pros and cons to this I know. But for my set up and use patterns its ideal.

Thanks all

 

 

Mike: you might have voltage drop due to poor ground or bad wiring. Have you checked the volts output at the alternator?  

Edited December 29, 2018 by damanic

[Bowie69]

The wire in that three pin plug does not look fat enough to run the heated rear window to me, I certainly wouldn't be connecting it up to the starter solenoid - that would end up with an undersized wire running an oversized load from an unused connection!

Unless of course you like marshmallows a lot

[western]

Be just as easy to add a decent size wire to alternator to run a changeover relay to switch the additional supplies you want, or get the split charge connected up properly & let that control the charge feed to batteries. 

[Craigmidlands]

On 12/28/2018 at 10:16 AM, damanic said:

That's what I thought western, so the brown wire 12v feed to the VSR comes from somewhere else and not via the three pin plug on bulkhead?  Any idea where I can look for the  loose connection?

The power to the vsr does come from that 3 pin connector and the cable in turn runs down behind the bell housing then along the chassis straight to the battery +