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| Vacuum Gauge and Battery Indicator Installation Problems https://www.ausmini.com/forums/viewtopic.php?f=2&t=47759 |
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| Author: | Flute [ Thu Nov 20, 2008 6:29 pm ] |
| Post subject: | Vacuum Gauge and Battery Indicator Installation Problems |
Just connected up three new instruments. A Smiths (new old style) clock, an old Smiths Vacuum gauge and an old Smiths Battery Voltage Indicator. The lights are all working, ran them off the tacho lighting that I had done previously. The clock works perfectly. The voltage (battery indicator) gauge has no movement. I have earthed it both sides and tried direct power and via ignition. Is there any trick to these? It doesn't move even connected to the battery direct. This is a resotered gauge so should work. Any thoughts? Also, the vacuum gauge needle is jumping all over the place like it is out of control. If I rev it steadies but that is the only time. The tiny hose is connected to its own outlet off the inlet manifold. I have temporarily disconnected it so I dont wreck the needle. Any ideas on this one? Iknow these gauges aren't really necessary but I had them and they are in a nice looking three gauge chrome holder which I have made sides for to make it all look neat and its sits under the dash on the drivers side right of the steering wheel. They are period accessories so I thought they might as well work. Cheers. |
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| Author: | Wombat [ Thu Nov 20, 2008 6:34 pm ] |
| Post subject: | |
I'd say the voltage gauge is stuffed if it doesn't work straight off the battery |
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| Author: | Morris 1100 [ Thu Nov 20, 2008 6:38 pm ] |
| Post subject: | |
The voltage gauge should work! One wire to pos and one to neg and it should read. There are no tricks. It should work when hooked straight to a battery. Vacuum gauge should pull about 20 (I think!) at idle and zero when you put the foot right down. On overrun it will pull higher maybe up to 30. They flap around as you blip the throttle. A constant throttle should show a constant (low) vacuum. |
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| Author: | Mick [ Thu Nov 20, 2008 6:52 pm ] |
| Post subject: | |
The vibrations in the vacuum gauge are caused by the rapid pressure fluctuations in the manifold as valves open and shut. They often fill these kinds of gauges with liquid to dampen the needle. You might try increasing the length of the supply vacuum pipe dramatically. This will see the fluctuations dampened over the length of the hose which will reduce the jumping somewhat. |
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| Author: | moemoke [ Thu Nov 20, 2008 7:18 pm ] |
| Post subject: | |
Maybe the Vacuum gauge is stuffed or it is not connected in the right place, I have mine connected into the inlet manifold not where the vac advance is, this can make a difference. From memory if the needle fluctuates when the engine is idling then that is a sign of faulty valves 
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| Author: | 64cooper [ Thu Nov 20, 2008 7:57 pm ] |
| Post subject: | |
Just out of curiosity, by restored, do you mean that it has been done by an instrument workshop? If so, take it back. I had a similar problem with one of my restored gauges and it turned out to be the needle stuck to the return post by the paint used in the restoration process. A solid tap on the front of the gauge when powered up shook it loose and no problems since. Just a thought. |
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| Author: | Flute [ Thu Nov 20, 2008 8:28 pm ] |
| Post subject: | |
Thanks all. Pretty sure I had the voltage guage restored at an intrument shop. It will go back for a check up (I'll check the paint on the needle first in case it is stuck!) . Vacuum gauge, not sure about. The hose is about 1/8" OD and about a metre long. It is connected to the inlet manifold with its own port on the left side with the brake booster hose on the drivers side. Running a 45 Weber, don't know if that would effect it though. Hope the gauge isn't so good that its telling me my valves ARE stuffed. If any air was getting in would that cause this? Might have to re think the connections at the gauge end. Cheers. |
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| Author: | 9YaTaH [ Thu Nov 20, 2008 8:54 pm ] |
| Post subject: | Hg |
Flute wrote: Thanks all. Pretty sure I had the voltage guage restored at an intrument shop. It will go back for a check up (I'll check the paint on the needle first in case it is stuck!) . Vacuum gauge, not sure about. The hose is about 1/8" OD and about a metre long. It is connected to the inlet manifold with its own port on the left side with the brake booster hose on the drivers side. Running a 45 Weber, don't know if that would effect it though. Hope the gauge isn't so good that its telling me my valves ARE stuffed. If any air was getting in would that cause this? Might have to re think the connections at the gauge end. Cheers.
As stated above, the vac line should be coming from your inlet manifold. Hard to say about the needle dancing around...but 1/8" OD vacuum hose sounds wrong...it should be the same size as your rubber vac hoses you have under the bonnet (so more like 1cm OD)....and should definately not be sucking air anywhere. I'm thinking about Bernoullis Theorem and higher velocities through the small pipe causing the fluctuations...then again...I could be thinking pure BS  
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| Author: | Flute [ Thu Nov 20, 2008 9:01 pm ] |
| Post subject: | |
It is coming from the inlet manifold. It has to be a small hose because that is how big the inlet is on the back of the gauge. I dont have a vac hose on the dizzy and it couldnt be as big as the brake booster hose. I will check for any leaks. Cheers. |
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| Author: | 9YaTaH [ Thu Nov 20, 2008 9:22 pm ] |
| Post subject: | Vac |
Flute wrote: It is coming from the inlet manifold.
It has to be a small hose because that is how big the inlet is on the back of the gauge. I dont have a vac hose on the dizzy and it couldnt be as big as the brake booster hose. I will check for any leaks. Cheers. Yep..from memory, the fitting at the back of the guage would be about 3/16" OD, but you slide the rubber vacuum hose over that. |
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| Author: | Flute [ Thu Nov 20, 2008 9:44 pm ] |
| Post subject: | |
Thanks, that may be the problem. I didn't have a fitting for the back of the gauge so an old bloke at a good old type of car parts shop helped by getting the brass bits which included two screw on nuts with a small rounded part in between (I asked what it was called but have forgotten but plumbers use them in gas fittings) The hose then went in and the nuts tightened. However I don't know that the seal is tight enough for the vacuum to work. If I pulled on the hose it would probably come out. The other end on the manifold has a proper slide on rubber hose which then goes on top of the smaller hose and is a very tight fit. I dont know if the correct fitting for the back of the gauge is available anywhere, the old bloke looked in the smiths catalogue and the only thing close was for a booster gauge and it was wrong for this gauge. May have to track down a second hand one. The hose I am using is more like plastic not rubber. The bloke new it was for a vacuum gauge so I hope that is right. 3/16 is probably what I have, I was just guessing 1/8th. I appreciate all your help. |
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| Author: | doogie [ Fri Nov 21, 2008 7:09 am ] |
| Post subject: | |
The Smiths volt metres do not read volts insantly, they take a while to come up & read the volts, typical Smiths product. Doogie |
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| Author: | drmini in aust [ Fri Nov 21, 2008 7:36 am ] |
| Post subject: | |
You will NEVER get a steady vac reading with a Weber or Dellorto, unless you put a small balance tube between the ports and attach it to that. When there is vac in one port, there is none in the other. 
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| Author: | Flute [ Fri Nov 21, 2008 9:09 am ] |
| Post subject: | |
Thanks 2 S's, I will hold it on the power for longer and see if it works instead of just touching it. Thanks Drmini, I was wondering about that. Might be easier to not use this gauge. It was only for nostalgia anyway. I had a balance pipe that I was running the brake hose off but it was too cluttered so now I run it off just the closest side. I have a two gauge holder that I could put the other two in. Might be the way to go. The clock has been handy, didn't think I needed one but now its there I use it. If nothing else though I have learnt a little bit about wiring and where things go. Pulling the immobiliser off made me work out where the wires go too. Cheers. |
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| Author: | peterw [ Fri Nov 21, 2008 12:16 pm ] |
| Post subject: | |
For the vacuum, maybe a plug in the line with a pin hole might slow down the reaction of the gauge to the vacuum fluctuations. I know they use that principle on mechanical oil pressure gauges. Pete |
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