One of my cars has a combo instrument where the water needle has stopped working. The combo instrument was overhauled about 3 yrs ago and the oil needle reads correctly.
As there is a speedo issue as well, I have the instrument board down and the combo instrument hanging loose. I removed the sender, which I have tried tapping many times, but before removing the fasteners along the carb mountings, to extract the long capillary tube,I thought I´d try immensing the probe/sender in a jug of very hot water. Ih had been boiling, but cooled off during pouring from one beaker to another. Hot enough to nearly burn my finger.
I then tapped the combo instrument with the back of a screw driver. The needle is now showing 55 which I think is correct.
The question now is, have I fixed it, and do I dare put it back and insert tge probe in the waterway and hope that it will be fine when I reinstall the speedo after a few weeks away for servicing?
I made a note 2 yrs ago that the water needle can easily read 95 when my dig thermometer says 85.
Advice will probably suggest sending it away, but I am just trying to see if I can keep it as is. The 2 capillary attachments to the 2 large carbs is a bit fiddly.
Any suggestions,
Peder
Since you have it off, take off the glass, hold the bulb in boiling water and see if the needle is tight on the spindle. It may be loose. Move it to 100 and press it down on the hub with your finger. Then remove the bulb from the water and watch the needle go down. That’s really all you care about, that it registers 100 when the coolant is 100. The rest of the range is for you to just watch for sudden climbing.
Thanks Rob,
I am actually in the kitchen, about to pack it for despatch to Richfield Speedograph in England.
I have done your test with boiking water and cold running water in the tap. It needs my finger to get it goingbut then moves to the right temp on its own. Tapping the glass before removal did not help. And when holding the bulb in running cold water, it also needs my index finger to push it lightly in tge right direction and it then settles there.
So something is stoppibg it from moving freely. The finger is tight on the axle. It is the sideways movement that it struggles with.
Peder
Ok something is causing the needle to hang up. Needle not dragging on the face, I presume? Then its the spring mechanism inside. Try dropping a drop of sewing machine oil down the shaft. Andrew the horologist would probably love to see it.
I have now gone from 100 deg boiling to cold tap water, about 10 times. I had to move the needle from 85 to 100 and now it moves freely, almost. I have pulled and pushed the needle to tge extreme ends and let the soring takebit back at full speed. It has probably freed it. Shall I put a drop of sewing machine oil along the axle, or was that a joke?
No, it wasn’t a joke, I was serious, oil inside can’t hurt it, it is a little bit like a clock.
I did drop a bit of oil down along the axle, but can´t really see a difference. I keep going up and down the temp scale from cold running water to boiling. The needle drags a bit. If I touch it, it catches up to true temp. Sometimes it does go all the way on its own.
Perhaps good enough to reinstall, and very different to the dead needle, parked on the pin at 10 degrees.
Interesting day, thanks to you Rob. I am now quite pleased with the functionality, and will reinstall tomorrow. I have done many more tests going up and down in temp with the bulb in a pan on the gas cooker.
Peder
Well, here is the only draw back: The needle won´t go back to the resting pin at 20 deg. It remains at 35-40, but goes to exactly 100 when the bulb is in boiling water. Not a major problem, but still not perfect. I could live with this, I suppose,
Peder:
If it is any consolation I do not think I have ever seen my temp gauge needle return to the pin, even when I look at it in the garage in January /February here in Canada. As Rob pointed out, what you really need to be interested in is the needle accurately going the other way.
Chris.