I'm sure this will have been covered before several times, but I can't fathom the keywords!

Basically I want to wire in an oil pressure gauge.

I have successfully wired in stuff before but everything ends up untidy. So what I'm asking is: Where is the neatest/most elegant place/way to draw current? (it has to be "ignition on" current, ie off when the key is out).

I'm sure this will have been covered before several times, but I can't fathom the keywords!

Basically I want to wire in an oil pressure gauge.

I have successfully wired in stuff before but everything ends up untidy. So what I'm asking is: Where is the neatest/most elegant place/way to draw current? (it has to be "ignition on" current, ie off when the key is out).

Heater blower switch or the radio?

Ok, whats the neatest way in terms of what crimps to use/ in line fuses etc? Can't remember what I did last time but it wasnt pretty nor safe/ reliable.

Best and safest way of making a connection is to strip away some of the insulation and solder the new wire to the old, the. If you can it's best to use shrink wrap to cover and insulate the connection. If it isn't possible then use insullatIng tape.

I'm guessing that the gauge is an electric type and not a mechanical type, meaning that the currant draw would not be much at all I would say around 2-3 amps at max, so pretty drawing off pretty much and power source behind the dash would be fine. As Nigel said heater blower switch or the radio are a good source to use.

HTH

cheers guys thats the info I was looking for!

If I'm wiring in several gauges, does that change things?

If I'm wiring in several gauges, does that change things?

The heater fan supply will be the better supply, as the cable is thicker so capable of carrying the greater current

As said, the heater FEED wire would be OK for the oil pressure gauge, but if you wish it to light up at night, you would also need a connection to the instrument lights.

When you say 'wiring several gauges' what exactly are you fitting? If that includes an ammeter, then that would need to be connected IN SERIES with the battery and the auxiliaries, you would also have to run the alternator output through it, or more correctly, through its shunt, which may be remote from the ammeter.

Regards.

Surely it's a bit bad practice to be splicing into cables to pick up power?

The wire sizes are calculated to run the components connected, meaning if you go putting more load it could overload the cables? Why would manufacturers spend more money and weight on using larger cables than necessary?

Ok picking up an ignition feed for a relay or something is ok ( they take what, 0.1a to switch?) but yeah.

Probably be fine, but I'm just saying.

Manufacturers are looking at running higher voltage systems on cars as thinner cable can be used, thus saving weight and cost, so I don't know how much tolerance there is on the standard cables before you're at the limits of their ratings.

As said, the heater FEED wire would be OK for the oil pressure gauge, but if you wish it to light up at night, you would also need a connection to the instrument lights.

When you say 'wiring several gauges' what exactly are you fitting? If that includes an ammeter, then that would need to be connected IN SERIES with the battery and the auxiliaries, you would also have to run the alternator output through it, or more correctly, through its shunt, which may be remote from the ammeter.

Regards.

Its an LED electric gauge so I presume it will light without the aformentioned extra wiring..

I'm also fitting a tach (hopefully).

As said, the heater FEED wire would be OK for the oil pressure gauge, but if you wish it to light up at night, you would also need a connection to the instrument lights.

When you say 'wiring several gauges' what exactly are you fitting? If that includes an ammeter, then that would need to be connected IN SERIES with the battery and the auxiliaries, you would also have to run the alternator output through it, or more correctly, through its shunt, which may be remote from the ammeter.

Regards.

Its an LED electric gauge so I presume it will light without the aformentioned extra wiring..

I'm also fitting a tach (hopefully).

You should be able to pickup the lighting supply from the heater control panel as well if you need it

Surely it's a bit bad practice to be splicing into cables to pick up power?

The wire sizes are calculated to run the components connected, meaning if you go putting more load it could overload the cables? Why would manufacturers spend more money and weight on using larger cables than necessary?

Ok picking up an ignition feed for a relay or something is ok ( they take what, 0.1a to switch?) but yeah.

Probably be fine, but I'm just saying.

Manufacturers are looking at running higher voltage systems on cars as thinner cable can be used, thus saving weight and cost, so I don't know how much tolerance there is on the standard cables before you're at the limits of their ratings.

As a general rule, you are quite correct, but we are talking milliamps here, so it is doubtful if the heater circuit would even notice the difference. Obviously it would be bad practice to take a heavier current from a cable which was intended to only carry light currents.

I would say that, if there is no other access to a supply, tapping into a cable as suggested above with a soldered joint and shrink-wrapped insulation, runs rings round these so called 'self-piercing' connectors, which either fail to pierce the existing insulation, or cut through some of the strands, talking of which, if you must tap into a cable, it is far better NOT to cut it through, but to carefully remove some of the insulation with a sharp knife, taking care never to break or cut any strands, as that most certainly will reduce the current carrying capacity of the original cable.

Regards.

I just tried to wire up the tachometer.. and failed to a certain extent it seems. Firstly the blowers have to be ON setting 2 or 3 in order for the gauge to turn on. Secondly it doesnt give a constant reading, fluctuating between 2000 and 4000 rpm at idle (the idle is steady).

As for the power source which wire do I go for? I went for the red power wire.

and the tachometer instructions say: 'on standard ignition, connect the green wire to the coil negative). I have done so, I can only assume the gauge is wrong for the ignition? But surely an old VW will have the simplest most common kind?

help appreciated.

i wouldnt run additional power sources directly from anywiring in the car,

use a 4 pin relay (30,85,86,87) and use the black wire from the ignition switch as the switch to turn on your relay, the feed from the relay should come directly from the battery. one relay pole goes to ground, the other to your instrument you wish to power.

if you google vw fuel pump relay wiring, you'll find diagrams of which each of the relay terminals relate to

does the tacho have a switch with 4, 6, 8 somewhere on it?

I just tried to wire up the tachometer.. and failed to a certain extent it seems. Firstly the blowers have to be ON setting 2 or 3 in order for the gauge to turn on. Secondly it doesnt give a constant reading, fluctuating between 2000 and 4000 rpm at idle (the idle is steady).

Is this not because the heater uses a resistor to vary the fan speed - so the voltage over the motor will change dependent on switch position. Clearly, at speed 2 or 3, the voltage across the motor is high enough that the meter turns on..

Sounds like you've tapped into the fan power feed, rather than the ACTUAL power feed..

You need to source a 12v ignition supply. If you can mock up a test lamp (a 12v lamp with two long wires). Hook one to ground and the other to a wire you think is 12v on ignition. It will light if the ignition is on, turn off when it's off. Now you know you've found your feed - tap into this..

Ok yeh I'm the wrong side of the switch! ha.

does the tacho have a switch with 4, 6, 8 somewhere on it?

Yeh, it does and I have positively identified the 4 cyl position.