VDO TEMP GAUGE READING WRONG

Includes wiring and battery, generating system, starting system,
ignition system, windscreen wipers, lighting system and instruments and gauges.

Moderators: reidy, Blacky

Post Reply
Dave
Posts: 107
Joined: Mon Nov 14, 2005 4:53 pm
State: NOT ENTERED
Location: Perth W.A.

VDO TEMP GAUGE READING WRONG

Post by Dave »

Hi guys.
I've got a vdo temperature gauge in the ute I bought recently.
I took it for a drive just on dark for the first time tonight. I thought the engine was overheating but noticed when I switched the headlights off, the temperature went back to normal. When the lights are on park the gauge goes up & when the headlights are on it goes up more.
Does anyone have any ideas what may be causing this? (Also the VDO oil pressure gauge goes down when the lights are on.)
Dave
My Band.....
www.myspace.com/thesuperdextas
Blacky
Posts: 12171
Joined: Tue Jul 20, 2004 8:58 am
State: WA
Location: up in the Perth hills

Post by Blacky »

Sounds like you could have a regulator problem , if you own a multimeter put it across your battery and switch the lights on and see if the voltage changes , the difference (if there is one) could be causing the problem, are both guages electric type ?
When you're faced with an unpleasant task that you really don't want to do, sometimes you just have to dig deep down inside and somehow find the patience to wait for someone else to do it for you.


Foundation member #61 of FB/EK Holden club of W.A.
Dave
Posts: 107
Joined: Mon Nov 14, 2005 4:53 pm
State: NOT ENTERED
Location: Perth W.A.

Post by Dave »

Blacky
both gauges are the electric type.
I'll do what you suggest, thanks.
There is also a voltmeter gauge that showed around 14v when the motor is running & 12 when it isnt which seemed right. Should the volts not drop when the lights are put on?
Dave
My Band.....
www.myspace.com/thesuperdextas
User avatar
Woodzy
Posts: 90
Joined: Tue Aug 21, 2007 5:34 pm
State: NOT ENTERED
Location: Newcastle
Contact:

Post by Woodzy »

Do you have the VDO illumination lamps connected to the headlamp switch circuit?
If so, you may not be earthing the VDO gauge body properly and the VDO gauge lamps may be finding their earth thru the sender units, causing the readings to alter when the park/headlights are on.
Just a thought.
Dave
Posts: 107
Joined: Mon Nov 14, 2005 4:53 pm
State: NOT ENTERED
Location: Perth W.A.

Post by Dave »

Sounds feasable. I dont know how they are wired as they were in the car already. I havent had a look yet. You would think someone would wire them to the dashboard light circuit (which I assume is separate to the headlights), but you never know do you. Thanks Woodzy.
My Band.....
www.myspace.com/thesuperdextas
rosco
Posts: 2569
Joined: Wed Feb 04, 2004 8:34 pm
State: VIC
Location: Melbourne

VDO temp gauge

Post by rosco »

Hi Dave,
I had a similar issue on the way back from Tenterfield - at Peak Hill my gauge needle went sky high - early morning on a cold day - pulled over and felt the lower hose on the radiator - cool............


pulled and prodded at the temp sending unit and found the wire to be finding an earth - apparently earth sends them up........

As for the lights scenario - assume nothing - if you didn't put it in, check it meticulously........
I am of the opinion, from what you describe, that the earthing of your gauge is suspect.
I am of the opinion it is pointing towards an earth issue as you state both gauges are affected and by the operation of the lighting switch.

The probability is the connections to both guages.....

The temp gauge I have is model number 999 161 019 - I don't know if this is the current or indeed the one you have fitted.

The oil pressure gauge I have is 999 161 011.

If you look at the back of these gauges there are in fact five (5) terminals......

The two at the top are for illumination - one to your instrument lighting wire which is coloured grey (this way you can dim the full set of gauges using your lighting switch dimmer) and,

one to earth (I would suggest to keep this separate from your temp/oil pressure indication earthing point).

At the bottom there are three - one directly to earth, one to the sender unit and one to a positive supply - generally from a "key on" input..

On both my gauges, the centre terminal of the lower indicator terminals is the direct to earth terminal (marked (-).
The other two terminals are marked as (+) for positive supply and
(S) for sender unit............. this is where I would suggest you start your investigation.....

There is a chance that whoever fitted these gauges, or someone who disconnected it and re-connected incorrectly has transposed the two negative indicator terminal connections - ie earth for sender and vice-versa.

This does not draw any conclusion to the "switching lights on" issue -
These connections should work entirely independent from the indicator part of the gauges.......

I would suggest taking a very close look at the way the gauge is connected and check all wiring for "earth leak" (short).

If you want a copy of the wiring diagram for the units I have - 999 161 019 (temp) and 999 161 011 (oil pressure) pm me and I'll email them.......

frats,
Rosco

ps
In answer to your voltage question - if you are running a generator - yes the voltage will drop until the generator output "switches" the voltage regulator on............

If you have modified it to alternator - because the output of an alternator is quite good at low revs, your voltage will probably only drop if at idle (or just above).
In both cases, voltage will of course drop to battery level (minus whatever the "draw") without generator/alternator output.
Around 14 v is good with engine running,
12 v normal for engine off.

Headlamps do draw a lot of current (along with tails & gauges).
karsten
Posts: 613
Joined: Wed Oct 17, 2007 6:31 am
State: NOT ENTERED
Location: bungendore nsw

Post by karsten »

it must be a vdo thing every kenworth i ever drove did the same thing with fuel and all the temps ,water, oil temp ,gear box ,and diff temps as well , my trucks does it with the fuel gauge reads fuller,, temp for water is a mercury switch which is more reliable but the diffs and gear box are electric and go up when lights are on
when they start building them like that again i will buy a new car of them
Dave
Posts: 107
Joined: Mon Nov 14, 2005 4:53 pm
State: NOT ENTERED
Location: Perth W.A.

Post by Dave »

Thanks for the input everyone, much appreciated. I'm sure I'll be able to sort it out with the info you all gave me. Gotta love this forum. :D
My Band.....
www.myspace.com/thesuperdextas
rosco
Posts: 2569
Joined: Wed Feb 04, 2004 8:34 pm
State: VIC
Location: Melbourne

diagrams

Post by rosco »

HGi again Dave,
for yourself and those interested, I had a play with the scanner today - results aren't great, but may give you a reference to follow.

I deleted all the foreign lingo from the diagrams leaving only English - if anyone wants the Deutch, Italiano, French, Espanol - I'm happy to re-submit the entire document.................

please find attached diagrams for 1 & 2 temp

temp gauge 1 - I did some editing and labeling to simplify what should exist.......

Image

temp gauge 2 is just the basic physical fitting

Image

3 & 4 oil pressure

Image

Image

frats,
Rosco
Mephious
Posts: 626
Joined: Thu May 10, 2007 10:01 pm
State: NOT ENTERED
Location: Sydney

Post by Mephious »

Hmmm my guess would also be an earthing issue. Somehow your getting increased voltage running back thru the gauge which could be caused by a high resistant joint.

More then likely you will find that the gauges and illumination share the same earthing point. This isnt a problem if your earthing is good on the body i.e good strap from the neg of batt to the chassis and block, no corrosion at the earthing point under the dash.

Simple solution is to run a temporary extended earth lead (4mm) from your battery and connect it to your bonded earth connection of your gauges un-attached to the car (just make-shift , bonnet up door open to under the dash). If this makes the gauges work normal you have it sorted.

From here if it does fix the problem, run a permanent cable back to the dash and mount it to a bonding terminal coupled to the body - you can pick these up at JR Turks etc ( go for a telecommunications bonding terminal , it will have one entry with 3 exits ).
[b] Member of FB-EK Holden Car Club Of NSW Inc. [/b]
Post Reply