Gauge help request

[hashman]

I am trying to finally fix my dials after many years with the temperature gauge not working.
Not sensible I know!
I have already had some help in the form of a colour wiring diagram from Paul Vernon and Roy Mawbey.
Thanks again guys.
My car is a late A '59 but has an SC engine so has been converted to electric rev counter. Although the oil pump cover still has the tach drive
Any way my question is about the back of the temperature gauge.
The wire from the sender seems to be redundantly waving about behind the dial.
The socket I believe it should be in is covered in a black sleeve with a tail...illustrated in picture.
Has anyone seen this black covered socket before?
Surely it should be connected to gauge somehow....
Any help greatly appreciated.
Karl

356wiring by karlhash, on Flickr

356wiring by karlhash, on Flickr

[Winston Teague]

Hi Karl, I think your green with black wire has a terminal on the end, which is still in the remains of it's socket. I think you should check that this is definitely the wire to the sender, by disconnecting the wire from the sender (hopefully also green with black) and doing a continuity check, between the ends, and then earth. There should be continuity end to end but not end to earth....
There seems to be a short, cut black wire in the connector on the gauge....There should, i believe, only be 1 wire in the sender terminal of the temp gauge, so what and why this wire is i don't know....
Also that scotchlock shouldn't be there, they are electrically & aesthetically dreadful........a chock block is less bad.....
Good luck and update please,if unsucessful keep asking, W

[Winston Teague]

I also think you will find fixing it easier if you drop the combi gauge out of the dash, undoing the mounts by braille is easier that connecting wires by braille. Remember that the gauge needs to be earthed to function....W

[hashman]

Winston, I checked the wire down to the sender with the buzzer function on my multi meter by making a circuit and it buzzed. The other end looked more brown and black but I think its just dirt.
Not sure if that is a full proof method or not.
As for taking the gauge out, that was my plan but i'm having trouble releasing the fuel gauge wire and I didn't want to break that one..
I shall give it another go tomorrow.
At the mo, its good exercise for the neck and stomach sticking my head under the dash.....

The scotch block is supplying power to the electric rev counter, but maybe this is the bad connection causing the rev counter to intermittently work!
And that would also mean there is power straight to the temp gauge which would cause it to flick straight to max when I switch the ignition on.
I'll swap them and see what happens.
Thanks Winston.

[Winston Teague]

Ah, if the temp gauge goes full scale when the ignition is turned on that may be because the wire to the sender, or the sender itself is shorting straight to earth. The gauge is simply a voltmeter, the sender a variable resistor (according to temp) with one end earthed. Full scale deflection is a good vital sign in terms of the gauge, but the short to earth could be anywhere in the wire to the sender, it could be in the output side of the gauge itself, or the sender itself. Remove any wires from that side of the gauge. The +6v side of the fuel gauge is a perfectly ok place to get +6v for the rev counter, but scotchlocks are crap. Intermittentness (intermittancy?) is often missing or iffy earths on the body of the gauges, there might be a daisy chain of ring terminals, one on a mounting leg thread of each gauge, these are fiddly to install and often get missed. and if the gauges still have their rubber o rings behind the bezels accidental earthing is a game of chance. I find if i need to get under the dash of mine it's easier to take out a seat, as my eyes now have a focal length that doesn't match my arms! I need to do a wiper motor change, lockdown project no. 467.......W

[hashman]

Thanks Winston that was great help.
I was able to get my head around the workings after reading that.
I managed to get the dials out in the end and was able to inspect the tiny wire in the black socket.
The use of my daughters hand held micro scope helped here as I have no magnifying glass.
It was a wire, so I soldered on the connector that was attached to the wandering wire.

20200501_185149 by karlhash, on Flicker

I connected it all up and the dial still flipped straight to max.
So took it all apart and tested the dial, but when I put negative and positive from the battery to the terminals of the dial it would only flick the gauge momentarily, when I would expect it to go to max.

20200502_184713 by karlhash, on Flickr

20200502_184644 by karlhash, on Flickr

20200502_184731 by karlhash, on Flickr

So I used the buzz tester again and the guage terminals showed a good circuit..........
Unsure what was going on, it seemed to make sense to swap the wires around.
Hey presto.......it worked.
After a quick drive this morning the guage even went up a little.
No vid just screen shot

Screenshot_20200503-205506_Video Player by karlhash, on Flickr

First time thats moved correctly in 17 years.
I even got rid of that connector block Winston
Took the time to wire wheel the knurled knobs, gauge bodies and brackets to get rid of thee surface rust.

20200502_110433 by karlhash, on Flickr

20200502_113322 by karlhash, on Flickr

20200501_172253 by karlhash, on Flickr

20200501_17225o by karlhash, on Flickr

Its a nice feeling having clean knobs after all this time....
I gave the jack a very quick clean also.

20200503_171729 by karlhash, on Flickr

This old radio shack voltage converter wasn't even connected to anything.....I used to think it was for the electric rev counter

20200503_170158 by karlhash, on Flickr

Which leads to the rev counter, it works better now at low revs but at higher speed it was dead so I shall check the grounds/earths.
I've purchased new LEDs for the dials so I'll put those in now I know stuff works.
Will post pics when the LEDs are in

20200501_172138 by karlhash, on Flickr

20200501_183211 by karlhash, on Flickr

Karl

[Kneeslider]

Yay! Its great when some fettling pays off. My temp guage was properly dead when I bought my car, so I ended up robbing the little card and needle out of the combo guage, and replacing the workings with those from a £6 Ebay guage and sender from China. The tough bit was making a brass adaptor up so that the new, smaller sender unit would screw into the housing properly, Because its something that works on resistance, it doesn't matter about the new bits being specified as a 12 volt guage. I calibrated the whole thing by dropping the sender into some boiling water (at sea level) and stuck the needle on so that 100°C read straight upwards.

Having said that, it seems to be very rarely that the needle moves much off the left hand stop, and only a few times on the motorway has it registered much to the right of centre.

[Winston Teague]

That's great, i've never seen the gauge out of the combo unit and so had no idea about the calibration figures at the top of the face. I now fancy calibrating mine which has a resistor as my car has been converted to 12v. W

[neilbardsley]

I believe straight up should be 100c? There is a post from Mike Smith on putting your sensor in boiling water to check. Sometimes you have to swap sensors to get a match?

Sent from my Redmi 7 using Tapatalk

[Mike Smith]

Here is what I probably put into print previously

I am always happy to be corrected, if you see anything that is rubbish

@@@@


The Oil Temperature Gauge is, in my opinion, the most important Gauge in the car


The generator Light is the most important `Idiot Light` - It may be Fan Belt Failure ?

Oil Temp Gauges – Porsche 356 & 912)


1. Gauges may be 6v or 12v depending on the vehicles Wiring
2. The Gauges are Volt Sensitive
3. The Senders cover a voltage Range from 6v to 24v
4. Gauges re-built by Palo Alto MUST be matched with the Sender Unit that they will include with the re-built gauge
5. I have no experience of the gauges re-built by any other company
6. The Faces of the gauges vary.
7. Early gauges are marked with the temperature in either Centigrade or Fahrenheit depending on the country that they were originally destined for
8. Late gauges have no readable numbers BUT they are actually there, extremely small and tucked up under the bezel
9. The Face of the gauge may or may not have a description i.e. Oil Temp – this depends on the year of the vehicle and again its destination
10. NOTE that Porsche measured the oil temperature in different locations through the life of the 4-cylinder motor so this also needs to be given some thought if the oil temperature is not running at around 100 degrees
11. Ignition Off - The Needle is parked on the left hand side up against a stop
12. Ignition On/ Engine Cold – the needle should move off the stop slightly
13. Motor at running temperature – Needle vertical
14. With the needle in a vertical position the oil temperature should be reading 100 degrees C if it is reading correctly

To Check the Gauge & Sender
1. Leave the Existing gauge in the car.
2. Take the sender out of its location (if it is a Carrera, you will need to plug off the hole in the oil Tank (obviously)
3. Leave the Positive Wire attached to the sender or extend it if necessary.
4. Wrap a bare wire around the body of the sender and earth it to the body of the car.
5. Put the end of the sender in a kettle and boil it
6. The needle should (or course) read 100 degrees C (212 degrees F)
7. If it does not – it can, of course, be either the Sender or the gauge BUT usually it is the gauge
8. The Oil Temp Gauge is held into the back of the Main Combination Gauge by 4-Small Screws
9. Remove the Main Gauge from the car (Taking GREAT Care not to break off the connections on the Oil Temp. Gauge or the Fuel Gauge – these are VERY Delicate)
10. Unscrew the 4 x small screws and change over your gauge for the new one or send it away for re-build
11. They are always exchange so all dealers will make a hefty core charge if they are supply one prior to having the old unit in their hands

[roy mawbey]

Well done Karl! Its a super feeling when you succeed! One of Mikes points is also valid as that temp gauge needle has on my car never gone past midway in 51 years of me driving it. In winter time its about 1/4 or a little more on a long run.

Roy