New Gauges

[Guest timswait]

I've got a set of gauges given to me by a mate (don't know what make they are, but they look pretty sweet, white on black, chrome bezels). The problem is that the Sierra water temp and fuel level ones I'm replacing have three connections, but the new ones only have two. I'm guessing that the three connections on the Sierra are +12V, earth, and variable level, and I can work out which is which, but should I use the variable and the +12V or the variable and the earth? There's no instructions of any kind with the new clocks.

[Guest Ant]

You need to trace back the wires in the wiring diagrams and on the tracks on the Sierra dashboard circuit board. There are two wires to each gauge. One from the voltage stabiliser (usually 10v (NOT 12v!!!)) and the other goes through the sender unit to a chassis earth. The sender (temp or fuel) is a variable resistor which restricts the current going through the entire circuit. The third wire is a common earth but I don't think it's used by the gauge.

 

The Sierra wiring diagrams vary depending on which model you started with, but there will be one wire going from the fuel sender into the dash cluster, and one from the temp sender into the dash cluster. The voltage regulator is also inside the dash cluster so you either need to pluck it out or get a replacement as a self contained unit. The gauges you have with 2 connections can be connected either way around as it's just a coil and a bi-metalic strip inside them. Just connect one side to the voltage regulator and the other side to the wire from the sender unit.

 

The new gauges will also need their case earthed - not for the gauge reading, but so that the illumination bulb is earthed. The bulb fittings usually have 1 wire going onto the end of the bulb, with the case of the bulb holder earthing through the case of the gauge. Hence the case of the gauge needs to be earther to complete the lighting circuit.

 

The voltage regulator needs a 12v supply which comes on when the ignition is on, an earth to the chassis, and the third wire is the output which goes to the two gauges. Again some voltage regulators are earthed through their case (often screwed to the back of a speedo). Mine is a Smiths type and has two connections labelled "B" for the "battery" (ie the 12 v ignition supply) and "I" for "instrument".

 

Some Sierra fuel senders have 3 wires leaving them not one. One always goes to the dash console and is the wire you want. The other two, if fitted, go the the aux display unit and they are used to put the low fuel warning lights on. I simply removed these extra two from my loom.

 

And now for the real problem ... gauges and sender units need to be matched. If you connect a Sierra temp sender to a Non-sierra temp gauge there a good chance that it will permanently read hot, permanently read cold, or only operate over a very limited area of the display. Same for the fuel gauge. If you talk to an instrument supplier they should be able to supply sender units which are matched to your gauges.

 

Ant

[Guest timswait]

:angry: Pants. More annoying than I thought. Turns out the gauges are meant for a bike so are meant for a 6v volt supply. Still they look pretty, so I'll try and sqeeze the Sierra electrical bits in and use the faces and bezels from the new ones.

[Guest timswait]

I've got the Sierra electrical bits into the pretty cases, and they seem to work, the problem is, I seem to have lost the position of the needle so they need recalibrating (for "recalibrating" read "pull the needle off and put it back on in the right position"!). Does anyone know the range of resistances that the temp and fuel level senders give when going from cold to hot and empty to full? Haynes manuals don't seem to have useful information.

[Guest Battery Bill]

Another Yarn from Ant I see

[Guest Ant]

Another Yarn from Ant I see     

Those of us with road legal Robin Hoods can afford to spend more time writing full and detailed replies!

 

When's your SVA Bill?

 

Ant

[Guest Battery Bill]

Ant

Whats the rush ?

If you go full speed ahead and finish the car in a desperate rush it causes stress (You have said it yourself)

You also end up making silly mistakes like fitting the tunnel panels on the wrong side with the sloping bit to the front instead of the back Meaning you have to make up another panel to fill the Hole

We also noticed your drainage holes where the rear arches fit the body

I thought you should not see them !

Sorry you asked for that...

You might have an SVA but me and my 12 year old son are still having a great time building the car. Why rush?