I have my engine on a test stand and getting close to the first start. I temp wired in my tach and temp gauge. Alternator is not connected. According to pics I’ve seen, the switched power goes to the spade marked with an arrow. Is that correct? The other space is my temp sending unit. Also, do I need to hook up a voltage regulator if this stand will hopefully be just temp? Gracias…
Yes you need to use it if you want accurate readings. Might be easier to just use an IR thermometer.
Can I just run a wire from my alternator that is voltage regulated internally?
Hi Steve
The voltage that operates the temperature gauge comes from the alternator and then goes through the little regulator that is bolted to the back of the dashboard before it arrives at the gauge. I forget the exact voltage but it is a saw wave of about 9 volts. If you want an accurate temperature gauge reading, you will need to use the little regulator
Dennis
That is not how my 69 S2 is wired.
The green/black on the right is the switched 10V from the voltage stabilizer.
The green/blue on the left is from the sender.
The deflection is caused by a heater so maybe it makes not difference to polarity?
Dennis
69 OTS
Could very well be. Though when finally wired in the car the wiring loom may dictate the connection.
As you’ll note in my photo above, Jaguar did not use one mm more wire than was absolutely necessary.
Regulated voltage to instruments is 10v I believe
The power required by the temperature gauge (and the fuel gauge) is 10V, supplied by the instrument voltage regulator. You should NEVER put full system voltage through the gauge. Just wire your system voltage to the “B” terminal on the IVR. Wire the “I” terminal to the gauge. Make sure you ground the case of the IVR.
And they aren’t called spades, they’re quarter inch disconnects or terminals.
When did that change?
When I search online for them, ‘spade terminal’ brings them up every time.
I thought they were ‘Lucar’ (if we want to get all pedantic).
Spade terminals are the u-shaped ones–like a ring terminal but not requiring that the screw to which it will be attached to be removed. What changed is that, about 20 yrs ago or so, quick-disconnects (tab, Lucar) terminals started being incorrectly called spades for some reason. Now it’s ubiquitous.
WEll, Ive been wrong for waaaay longer than 20 years!
I think I’ll stay a ubiquity!
Hahaha! I shouldn’t say incorrectly, consumers can change the name whenever they want. It’s incorrect only in that the “true” spade connectors (5 pages of them below from a major vendor) now lack a unique descriptive name.
Just researched it–you’re right. Evidently (from Wiki), what to call these terminals was first considered by the Greek scholar Plutarch in the first century AD. 
I’ll respectfully follow your sage advice, since you were there…
Thanks guys. More wiring to follow.