View source for 7 Volt Regulator

===7 Volt Regulator=== 
<span style="color: #000000;">Information courtesy of Reg in Bristol</span>

<span style="color: #0000bf;">1:Set Multimeter to 20v DC range.</span>

<span style="color: #0000bf;">2:Open the green/blue leads connector to the rear of the thermostat under the tank and</span>
<span style="color: #0000bf;">measure the voltage form the gauge when the ignition is on to the frame/ground.</span>

<span style="color: #0000bf;">It should be around 6.75v to 7v DC</span>

<span style="color: #0000bf;">If this is ok suspect the sender unit itself which is housed in the the thermostat housing.</span>

Home-made
Alternative 7V Voltage Regulator

Warning!!!.Only use 5mm Green LEDs. Not any other size.

The 7v regulator is used to give a steady power supply to the
Temp and Fuel gauges.
They can often give a high output when failing and overdrive the gauges.
This can get you pulling the cooling system apart before you realize
you have a fault in the Regulator.
I find the easiest way to check the output is to take a reading on
the bullet connector to the rear of the thermostat with the ignition on.
It can be done with the tank on but its no big deal to remove the tank
on a ZAB type CX.
In the pic below is a failed regulator.
The red arrow points to a split in the casing due to overheating.
The other one has my DIY version fitted into an original case.
I usually try and use the original leads too.
but in this case they had been chopped off.

 http://i42.photobucket.com/albums/e315/sheppola/7vreg.jpg 

I have had a couple of these on extended test for quite a while now
with no problems reported.

Component cost is about £1
Here's the circuit:

 http://i42.photobucket.com/albums/e315/sheppola/7_vr1.jpg 
Crude maybe, but effective and pretty reliable too.
The fuse is optional and so is the 0.1uf cap on the output.


HOW IT WORKS

The chip controls the output voltage with reference to ground.
So, what we do is bump up the ground by putting a green led between
the 0V pin and ground. This usually gives around 6.95V.
That's near enough.
A red LED will give about a 6.5V output, yellow 6.75V
so use green OK?
The heat sink is essential!
The chip has to dissipate heat and a heat sink will allow it to
do that without damage.
The output cap is non-essential, its a crude circuit and
minor fluctuations will go unnoticed.
I've never bothered to fit them.
The 7805 IC is common as muck and cheap too.
It is rated at 1 amp and the 78S05 2 amps.
If I wanted to drive two gauges I'd use the 78S05.


Assembly tips:
The 7805:
When laid on its back the pins are from left to right:
Input (red)- Ground (green) - Output (yellow) The input connects to ignition live which on the CX is a black cable
The Ground has the green led between itself and ground.
Output goes to the temp gauge.
 http://i42.photobucket.com/albums/e315/sheppola/7805-1.jpg ............ http://i42.photobucket.com/albums/e315/sheppola/diode.jpg 
The green LED
The longer leg is the anode or positive leg (red arrow).
This is the leg that must attach to the centre pin of the 7805.
The shorter leg is the cathode (green arrow).
This is usually denoted by a flat on the clear body as well.
This leg connects to ground.

Soldering:
Don't overheat the 7805 or LED as this may damage/ruin them!
Tin (pre apply solder) the cable ends and legs with solder then the briefest touch with
the iron should attach them to the 7805 and LED.

I use heat transfer compound when fixing the 7805 to the alloy heat sink
with a small nut and bolt or pop/blind rivet.
I also test it before potting the circuit in epoxy or hot melt glue.

Here's a pic of one on my bench.
I try to keep them as compact as possible so I can fit them
into the original cases and have as large a heat sink as possible.

 http://i42.photobucket.com/albums/e315/sheppola/chipandled.jpg  http://i42.photobucket.com/albums/e315/sheppola/chipandled2.jpg 

If you use a different method, be warned that if the heat sink shorts to
ground, the output will drop to 5V as this will in effect bypass the LED and it will behave like a normal 7805.

Insulator kits are available for this type of IC and cheap too should you want to use them.

[https://sites.google.com/site/cx500gl500/7volt Source]