sender unit ohms - 1978 CF

[aussieneil]

Hello all. I've trolled the forums, but can't find an answer.

My '73 CF has a '78 dash fitted (which looks a little different from the '73 I replaced, but I assume the gauge mechanisms are much the same), but recently the temp guage has started to act erratically, reading occasionally (and suddenly) extremely high before settling down again.

I doubt it's the voltage regulator on the dash, as the fuel gauge stays constant.

If I take out the sender and give it a whack it settles down for a while, but obviously this won't be a long-term fix.

I removed the Holden sender from a head I had lying around, but when I fit it the gauge instantly reads hot (in the red).

Measuring resistance with an ohmmeter I discovered the Holden one reads about 270 ohms at room temp, while the erratic original measures about 1300 ohms (1.3 kilohms) when operating correctly.

At 1.3 kilohms the guage is accurate, coming up to near half before the thermostat opens, then settling down to about 1/3 for normal running. From past experience I also know it goes into the red when things are really hot and bothered under the bonnet.

So, counter to all the advice I've read in the forum so far, the Holden senders won't suit - they're all around 300 ohms or less.

Has anyone experienced the same thing, and know where I can source a sender that is around 1.3 kilohms cold? Maybe Smiths rather than VDO? The only markings on the 'proper' sender indicate it was made in the UK, and has the code AC4751 (possibly 4761) on it.

Any guidance appreciated.

[Hobbit]

Hi Neil,

Is your engine a Holden 173 Red?

I have read that Holden originally used VDO Instruments.
After having my temp gauge measured, I was recommended to use a VDO 320-033 temp sender.
It still read a bit hot, so I added a 5 ohm resistor on the sender to get the gauge to read correctly.

Holdenpaedia says;

VDO temp sender no. 320-002 for HD, HR, HK, HT, HG, HQ and LC, LJ Torana.
The resistance range is 287 - 23 ohm

VDO temp sender no. 320-003 for HJ, HX, HZ and LH, LX Torana
The resistance range is 282 - 40 ohm

You need a thread adapter with these, VDO 320-053                                  Hope this helps.

[aussieneil]

Thanks for the comprehensive response.

Yes, it did have a 173 from 1973 until a few weeks ago, when a specially-built 202 (high compression head with stainless valve seats, special LPG 'towing' Wade cam, and full recondition by H&V Pearce at Long Gully, Bendigo) was fitted.

The sender is from the 173, where the 202 (originally fitted to a Holden car) came with the usual 300-odd-ohm sender which doesn't work with my gauge.

What I've decided to do, to prevent spending endless dollars on senders that don't work properly, is purchase a 1-watt 2.4 kilohm wire-wound potentiometer, and accurately measure the ohms where my gauge reads cold, middle and hot, and then look for a sender that approximates those readings. I take your point that it will probably be necessary to add a resistor to get things where I want them.

Now the camper has full, accurate VDO instrumentation for everything else (oil pressure, vacuum, voltage, tachometer), I may as well get the engine temp showing correctly too!