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Mon Sep 28, 2009 9:34 pm

Hi. I posted this over in the Ghia area, and relized I probably should have posted here. two questions:

1) I bought a Ghia that came with three VDO gauges (oil temp, oil pressure, cylinder head temp) that need sending units to make them work. VDO recommends 16-gauge wire to connect the gauges to sending units. Can I use 18 gauge? I'm tempted because I've found cable that contains four strands of 18-gauge, which would make the wiring simpler and cleaner. Haven't found bundled 16-gauge locally.

2) for the CHT gauge, I have the gauge and the sending unit, but not the 15-foot of wire that VDO sells to connect the two. Is there anything special about the connecting wire? Can I just substitute regular 16-gauge (or 18-gauge)? Although VDO seems to sell a 15-foot length of wire designed to connect the sender to the gauge, I'm having trouble tracking one down.

thanks for any advice on either question.

Mon Sep 28, 2009 9:54 pm

Vdo recomends 16 guage, so I would stay with it. There may be resistance difference which would affect the reading on the guage.

Tue Sep 29, 2009 6:16 am

This place has all of the correct, SAE automotive, wire you will need in as little as 20' lenghts

http://www.kayjayco.com/catPWireGXLTXL.htm

Tue Sep 29, 2009 10:23 pm

ghia7t1 wrote: VDO recommends 16-gauge wire to connect the gauges to sending units.
That's laughable! 16AWG is capable of carrying 20+ Amps. The current through the sending units is measured in mA.

I used a bundle of 4 conductor 22 AWG wire for my VDO guages, installed about 15 years ago.

Wed Sep 30, 2009 5:19 am

Go bigger on the minimum wire size recommended but not smaller.

Wed Sep 30, 2009 6:31 am

Maybe VDO calculated the wire resistance for that size/gauge wire so as to give the most accurate reading on the meter, like the general posted earlier

Wed Sep 30, 2009 11:13 am

1) I agree with the earlier statement. Do not use a smaller than recomended wire.

2) I believe the VDO head temp sensor is a thermocouple. If so you would need to use the proper type of thermocouple wire between the guage and the sensor. Regular electrical wire won't work.

Thu Oct 01, 2009 8:26 am

The VDO CHT is not temperature compensated, you have to at the very minimum, run the thermocouple wire inside the car. You can then extend it to the gauge with regular copper wire. What wont work is to terminate it inside the engine compartment.

As for having to use #16 as signal wire is totally unnecessary. Does anyone really believe that VDO ran current tests with different gauges? Someone determined that every mechanic has access to inexpensive #16 hookup wire AND the most common crimp-on connectors that are designed for #14-16 wire. 18-22 requires different terminals, which are available, but not as common. I run #20 aircraft wire to sending units just because I have a large supply.

Fri Oct 02, 2009 12:20 am

runamoc wrote: Maybe VDO calculated the wire resistance for that size/gauge wire so as to give the most accurate reading on the meter, like the general posted earlier The difference in resistance between 16AWG and 22 AWG is two-tenths of F#$K-all. The resistance of the sending unit is thousands of times greater.

I think the real reason they recommend heavy gauge wire is for strength. The 22AWG wire I'm using is quite feeble at the crimp for the connector.