S1 oil pressure & fuel 'idiot light' switch / sender
Discussion
At long last the end of the 'quick' (the only thing quick being how quickly it snowballed!) recommissioning journey for our '88 S1 is in sight 
It's been a far bigger job than anticipated, but it's looking great now and should be good for many years to come. Having sorted the major jobs I've finally made my way down the list to some of the incidentals that I'd like to sort, like some of the warning lights that have never worked.
I have the crescent of lights under smoked perspex to the left of the steering column on the centre console and amongst them is the oil pressure light. It's never worked to my recollection (there's an oil pressure gauge to monitor anyway) but it would be nice if it did.... Having whipped off the transmission tunnel trim piece, I find there is only one (green) wire going to the light.... I've found another black with white striped wire that's in the same vicinity but disconnected although I don't know if this is related. That set me looking for the oil pressure switch to follow the wire back from the engine.... but I can't find one! I have what looks like the oil pressure gauge sender situated on the side of the block just behind the thermostat housing with one wire coming from it (presumably feeding the gauge), but nothing else.
Is there no oil pressure switch on these? Perhaps the oil pressure lights were never wired in? or perhaps my gauge sender has been replaced and would have originally been a two wire? either way there is no sign of a spare wire to drive the oil light anywhere..... Am I looking in the wrong place? where would the oil pressure switch normally be?
At the same time I was looking at the above, I looked at the low fuel warning light as that doesn't work either..... I found that doesn't have any wires connected to it at all! I presume it would have originally worked or it wouldn't have been fitted.... but, well it's a TVR, so anything is possible! Maybe the black with white stripe wire (as above) is the driver for the low fuel light? How is the low fuel warning light switched?
I can't find a wiring diagram for the S1 that has the warning light circuits and wire colours shown anywhere.
Is anybody able to offer any pointers? Any help greatly appreciated!
It's been a far bigger job than anticipated, but it's looking great now and should be good for many years to come. Having sorted the major jobs I've finally made my way down the list to some of the incidentals that I'd like to sort, like some of the warning lights that have never worked.
I have the crescent of lights under smoked perspex to the left of the steering column on the centre console and amongst them is the oil pressure light. It's never worked to my recollection (there's an oil pressure gauge to monitor anyway) but it would be nice if it did.... Having whipped off the transmission tunnel trim piece, I find there is only one (green) wire going to the light.... I've found another black with white striped wire that's in the same vicinity but disconnected although I don't know if this is related. That set me looking for the oil pressure switch to follow the wire back from the engine.... but I can't find one! I have what looks like the oil pressure gauge sender situated on the side of the block just behind the thermostat housing with one wire coming from it (presumably feeding the gauge), but nothing else.
Is there no oil pressure switch on these? Perhaps the oil pressure lights were never wired in? or perhaps my gauge sender has been replaced and would have originally been a two wire? either way there is no sign of a spare wire to drive the oil light anywhere..... Am I looking in the wrong place? where would the oil pressure switch normally be?
At the same time I was looking at the above, I looked at the low fuel warning light as that doesn't work either..... I found that doesn't have any wires connected to it at all! I presume it would have originally worked or it wouldn't have been fitted.... but, well it's a TVR, so anything is possible! Maybe the black with white stripe wire (as above) is the driver for the low fuel light? How is the low fuel warning light switched?
I can't find a wiring diagram for the S1 that has the warning light circuits and wire colours shown anywhere.
Is anybody able to offer any pointers? Any help greatly appreciated!
The wiring diagram linked to above shows that neither oil warning nor low fuel lights were actually fitted. 
To wire up the low oil pressure you'll need a switch and a T piece something like these.
Find an ignition fed live, take to light and other side of light to the switch. Old PH thread here
To get the low fuel working you'll need a three wire sender unit in the tank, bit like this one, and of course abit more wiring
To wire up the low oil pressure you'll need a switch and a T piece something like these.
Find an ignition fed live, take to light and other side of light to the switch. Old PH thread here
To get the low fuel working you'll need a three wire sender unit in the tank, bit like this one, and of course abit more wiring
Edited by phillpot on Thursday 11th April 13:56
Does that mean that the lights were fitted as standard but not actually wired in? I wouldn't be surprised... but it would be interesting to know.
I'll have a look and see what I have / if there's room for a T-piece and pressure switch for the oil light.
For the low fuel light I'll have a look at the sender and see how many wires it has. If it's only a two wire (earth and potentiometer) I might look at the old Scimitar / Triumph system as an option and use one of their low fuel relays (essentially a gauge in a can that makes a contact to switch on the light when the resistance of the potentiometer reaches a certain value) as these can be piggy-backed off the existing gauge sender wire.
It would be lovely if something was just.... simple!
I came to do the rear brakes to find there was no way of accessing the automatic adjusters so I could slacken them and pull the drums off ..... nothing a mighty puller couldn't sort, but an awful lot of faffing about for something that should be routinely simple! A small hole drilled in the face of the drum before refitting has resolved that issue, but honestly!!
I'll have a look and see what I have / if there's room for a T-piece and pressure switch for the oil light.
For the low fuel light I'll have a look at the sender and see how many wires it has. If it's only a two wire (earth and potentiometer) I might look at the old Scimitar / Triumph system as an option and use one of their low fuel relays (essentially a gauge in a can that makes a contact to switch on the light when the resistance of the potentiometer reaches a certain value) as these can be piggy-backed off the existing gauge sender wire.
It would be lovely if something was just.... simple!
I came to do the rear brakes to find there was no way of accessing the automatic adjusters so I could slacken them and pull the drums off ..... nothing a mighty puller couldn't sort, but an awful lot of faffing about for something that should be routinely simple! A small hole drilled in the face of the drum before refitting has resolved that issue, but honestly!!
Haha! Ok, well that explains why they've never worked! Well I never .... thanks for posting the picture - I assume that's out of the handbook? (which I don't have).
In which case that's another tick off my list of wiring issues to sort.... there was never an issue in the first place! Good news.
Just need to decide if I'd like to upgrade their functionality now. Thank you.
In which case that's another tick off my list of wiring issues to sort.... there was never an issue in the first place! Good news.
Just need to decide if I'd like to upgrade their functionality now. Thank you.
I fitted one like this. Not from this particular supplier: there are loads on eBay.
One terminal grounds the pressure gauge through its internal sensor resistance, connected to the existing wiring. The other terminal needs wiring to a spare (unused) warning light ('MIL' on my S3). It too grounds the circuit (on a low oil pressure) so the bulb needs a supply from a suitable point in the dash wiring.
This works perfectly: the gauge on my knackered engine shows about 32psi at 2000rpm hot (ought to be 36psi minimum), and the warning light just about flickers at tickover when hot; just what I'd expect!
One terminal grounds the pressure gauge through its internal sensor resistance, connected to the existing wiring. The other terminal needs wiring to a spare (unused) warning light ('MIL' on my S3). It too grounds the circuit (on a low oil pressure) so the bulb needs a supply from a suitable point in the dash wiring.
This works perfectly: the gauge on my knackered engine shows about 32psi at 2000rpm hot (ought to be 36psi minimum), and the warning light just about flickers at tickover when hot; just what I'd expect!
Good man John, I have ordered one of those.
It is very difficult to fit a T piece into the engine, I bought one and tried but there wasn't enough space to get the gauge sender and a normal sender in with sufficient clearance to be sure they weren't going to get damaged. I didn't want to risk losing the oil that way! The oil warning light certainly wasn't wired on mine but I have added the wiring so one of those switches should be very good news.
I did have a recent 'oil pressure' issue. One of the few wires I haven't replaced is the one to the sender. All of a sudden the oil gauge dropped, then started jumping up and down. Bit of a panic for a moment. Eventually traced to that short length of wire gradually failing in fatigue inside the plastic outer, a kink in the wire turned out to be where the strands of wire had parted. That was a BIG relief!
One very worthwhile mod I did was to move the indicator tell tale light from the bottom of the set of warning lights. An MOT tester almost failed it years ago because he didnt think any tell tale was working! It was dead easy to position it between the revcounter and speedo, and I can actually see it now!
It is very difficult to fit a T piece into the engine, I bought one and tried but there wasn't enough space to get the gauge sender and a normal sender in with sufficient clearance to be sure they weren't going to get damaged. I didn't want to risk losing the oil that way! The oil warning light certainly wasn't wired on mine but I have added the wiring so one of those switches should be very good news.
I did have a recent 'oil pressure' issue. One of the few wires I haven't replaced is the one to the sender. All of a sudden the oil gauge dropped, then started jumping up and down. Bit of a panic for a moment. Eventually traced to that short length of wire gradually failing in fatigue inside the plastic outer, a kink in the wire turned out to be where the strands of wire had parted. That was a BIG relief!
One very worthwhile mod I did was to move the indicator tell tale light from the bottom of the set of warning lights. An MOT tester almost failed it years ago because he didnt think any tell tale was working! It was dead easy to position it between the revcounter and speedo, and I can actually see it now!
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