Oil pressure gauge reading low after reassembly

Recently I had my instrument cluster out to tidy up some wiring and whilst I was at it I repainted all the needles on my gauges. Upon reassembly the oil pressure gauge is reading lower than normal under all circumstances, ie ignition on and engine not running, cranking, engine running whilst both cold and warmed up.

When the ignition is on and the engine isn't running the needle is now sitting below the usual no pressure position/off the scale low.

Mechanically nothing has been touched or changed and I have no reason to suspect actual low oil pressure.

Even with the ignition off the needle is sitting in a lower position than it used to.

When I painted the needle on the gauge only the lens was removed and no other internals of the gauge were touched.

The wiring that I tidied up was all unrelated to the oil pressure gauge.

This is the std GMH/VDO GTR oil pressure gauge.

So,has anyone got any ideas on what's going on and how to rectify the problem?

Thanks in advance

James D

You must have accidentally moved the needle slightly on the shaft for the needle to be sitting lower than before when the gauge is powered down.

Thanks Dave,
That sounds feasible. I had wondered along the same lines but nothing stood out from memory.

Could the weight of the paint be holding the needle down, I know it sounds odd but it it is only a very light needle a small weight could make a difference

^ Agree

I reckon weight of the paint effecting the needle has been touched on in another thread somewhere.

Could the weight of the paint be holding the needle down, I know it sounds odd but it it is only a very light needle a small weight could make a difference

That could be true for reading lower when the ignition is on and when the engine is running but not when the ignition is turned off.

 

Quote 'When the ignition is on and the engine isn't running the needle is now sitting below the usual no pressure position/off the scale low.

Mechanically nothing has been touched or changed and I have no reason to suspect actual low oil pressure.

Even with the ignition off the needle is sitting in a lower position than it used to.'

Yep. Too much paint on the needle.

I think that idea of the weight of the paint on the needles once repainted was brought up in Marty's build thread when he was doing the same.

It's definitely a possibility as the needles and their associated springs feel very light, but so far it seems that this is the only gauge affected. Atleast from what I've noticed so far.

Too heavy handed with the paint?

There is a cam type arrangement that allows adjustment of those four needles. I wouldn’t have painted them. Especially the tacho and speedo needle.

Edit: LH/LX

Edited by hanra, 02 December 2018 - 11:54 AM.

From memory there's no cam adjustment on the rear of the gauges on the LC/LJ Torana's. Unless there's an internal one.

If the weight of the paint is a possibility then would rotating the needle on its shaft to effectively recalibrate it it work or would this cause other problems?

Paint on those 4 needles shouldn’t affect them as they are mechanically driven from a bimetallic mechanism, tac and speedo can be affected by paint as Hanra stated as they are not a mechanical mechanism like the other 4 if LH/LX insruments

Edited by ReplicarSLR, 05 December 2018 - 05:22 PM.

I've refurbished many of these clusters, and I can tell you for sure that paint on the pointers of the small gauges will not affect the readings at all, put as much as you want on, it won't make any difference.

 

Also it won't affect the speedo either unless you pile it on like a lunatic.

 

It will DEFINITELY affect the Tacho and the Tacho movement needs to be re-balanced, every time, no matter how little paint has been put on it.

 

There are in fact cam adjustments on the VDO Bi-metal gauges in the pod, but don't touch them unless you know what you're doing.  There is a factory zero adjustment and a span adjustment (for range) and they need to be done in sequence each time (special tool required).  Messing around with these will take your gauge to a place where you won't be able to find your way back to where it started and you'll wish you never touched it.

 

The most likely occurrence here is that the op has moved the pointer while painting it and the pointer just needs to be (delicately) twisted back to where it should be.  Normally that means re-calibration, but since you probably don't have the means, just first put the pointer back to where it used to be (by memory).  That's the best you can hope for under the current situation.

 

Important note:  If you remove the square centre cover of the small gauges, there are two little legs behind it which need to be BEHIND the pointers related to it (to keep the pointers all resting in a similar spot).  Not doing this will result in those two pointers being held back by the little legs and not reading at all and ultimately dislodging the pointer hip from the bi-metal.

 

Good luck, be gentle, and contact me if you need help.

Edited by VDO, 08 December 2018 - 10:51 AM.

Hi Chris,
Thanks for your advice, I was hoping that you might stumble across my question.

I took a photo of the cluster both before and after so I can use that as a guide to help reposition the needle. Would you suggest holding the shaft that the needle is mounted to in position whilst moving the needle to the appropriate position?

If the amp gauge has always been out of calibration by not sitting on zero with the ignition off then obviously this could benefit from being adjusted too.

Good idea to take a photo.

 

Don't need to hold the shaft, I don't think you can without some disassembly, and I don't recommend that... just tweak the pointer around until it stops in whatever direction it needs to go and then tweak a little more until it moves by the amount you need.  A little fiddling back and forth and you'll get there.

 

Same with the Volt gauge, however if it reads correct when the vehicle is running, then I wouldn't change it, or it will end up read low (obviously).  The Volt gauge is a slightly different animal to the other three, in that it runs on full 12v where the others run 5v.  The Volt gauge is notorious for getting a bit burned due to the higher load on the windings and it's often a bit out of whack due to that, which is not uncommon.  Be careful with it.

Edited by VDO, 08 December 2018 - 01:46 PM.

James, if the pointer (needle) of the oil pressure gauge needs to sit higher at the low end of the scale gently move the pointer to High until you feel the pointer stop, then gently twist or push the pointer a whisker further. The pointer's hub should move on the shaft without much effort. I've actually seen/fixed gauges where the pointer assy has fallen off the shaft.

Good idea to take a photo.

 

Don't need to hold the shaft, I don't think you can without some disassembly, and I don't recommend that... just tweak the pointer around until it stops in whatever direction it needs to go and then tweak a little more until it moves by the amount you need.  A little fiddling back and forth and you'll get there.

 

Same with the Volt gauge, however if it reads correct when the vehicle is running, then I wouldn't change it, or it will end up read low (obviously).  The Volt gauge is a slightly different animal to the other three, in that it runs on full 12v where the others run 5v.  The Volt gauge is notorious for getting a bit burned due to the higher load on the windings and it's often a bit out of whack due to that, which is not uncommon.  Be careful with it.

Hi Chris, Just to make you aware the gauge in question is for LC/LJ not LH/LX.

Are you sure..?  If so, that changes everything.

 

So the op dismantled the small individual GTR gauges..?  Removed the bezel and lens etc..?

 

The LC LJ movements are cross-coil magnetic, not bi metal.

 

Can you confirm we're dealing with LC LJ..?

The LC LJ gauges are all 12v.

 

Temp, Fuel and Oil are cross-coil (magnetic) movements.

 

If you've opened them up, then just move the Oil pressure pointer to where you think it should be.

 

As for the Amp gauge, it will need to be completely removed from the can, and carefully adjusted until it points exactly at the vertical (zero) position at rest.

 

To do this, look below the dial and there's the shaft that holds the pointer, at the base of that shaft is a small magnetic disc which is part of the "shunt".

 

You need to gently hold the disc with one finger, while moving the pointer as much as you think it needs.  It will take a couple of attempts back and forth until it sits correctly.

Here's silly me giving a whole tutorial on the wrong model... Duh... 

Are you sure..?  If so, that changes everything.

 

So the op dismantled the small individual GTR gauges..?  Removed the bezel and lens etc..?

 

The LC LJ movements are cross-coil magnetic, not bi metal.

 

Can you confirm we're dealing with LC LJ..?

Correct. James states it is a GTR oil pressure gauge in the original post.

Yep, hopefully the new info will help.

 

Sorry 'bout that James.

Edited by VDO, 08 December 2018 - 04:02 PM.

Yep, hopefully the new info will help.
 
Sorry 'bout that James.

No worries, thanks for both lots of advice. Luckily I hadn't rushed into the adjustments with the wrong model information.

Here's the after photo.

https://www.flickr.c...2478@N02/XK8e9U

Looking at your pic there James, yep definitely the needle has moved on the shaft.

The needles weren’t too bad before I painted them, they were better than most GTR clusters but I had most of the dashboard pulled apart so I did these and the needle on the factory radio whilst they were out. I also ended up respraying the black rings that hold the lenses on the gauges, gave the lenses a polish, fitted LED globes as discussed in another thread and repaired any poorly modified wiring. Next is to modify the windscreen demister ducting so that it can't rattle occasionally. I had also tracked down a pair of the L shaped speed nuts to secure the bottom of the cluster of 73 models, I ended up finding one of the original missing ones inside the dash. As you can see I had all these little jobs to do but I had put them off until I was ready to tackle them all together.