fuel & temp gauge reading to high.

Technical advice Q&A
User avatar

Topic author
Paul Jorgensen
Posts: 42
Joined: Wed Oct 26, 2016 7:28 am
Location: Southampton
Great Britain

#1 fuel & temp gauge reading to high.

Post by Paul Jorgensen » Tue May 14, 2019 2:35 pm

IMG_5662.jpg
IMG_5662.jpg (135.14 KiB) Viewed 1023 times
IMG_5665.jpg
IMG_5665.jpg (126.28 KiB) Viewed 1023 times



Hi All,

Ever since I have had my car, the temperature gauge every now and again has crept up as shown in the first picture, which to be honest was worrying. I did all the usual checks and could not find anything obvious.
In the end I purchased an infrared laser thermometer which I carried in the car, when the temperature crept up I would pull over and check the temperatures around the engine. All was reading normal.
In time I noticed that when the temperature gauge went up so to did the fuel level in my tank... I wish!!!! but the gauge did. That's when I thought, maybe it was the voltage regulator, I replace the regulator and it is still the same.
Although I know it is not overheating it still is worrying when it happens. Not sure if it would make any difference but it has a dynamator fitted in place of the dynamo.
Could anyone offer any help to overcome this problem or have had similar experiences.

The 2 pictures were taken last night on my way back home from its Mot test. The next 2 pictures were taken a few minutes later, I was sat in traffic and the Ammeter was reading - charge
Thanks
Paul
Paul. 1962 Series 1 roadster 850543
1965 mk 1 Lotus Cortina
1973 Triumph Stag (had it since 1982)

Link:
BBcode:
HTML:
Hide post links
Show post links

User avatar

Topic author
Paul Jorgensen
Posts: 42
Joined: Wed Oct 26, 2016 7:28 am
Location: Southampton
Great Britain

#2 Re: fuel & temp gauge reading to high.

Post by Paul Jorgensen » Tue May 14, 2019 2:39 pm

IMG_5650.jpg
IMG_5650.jpg (123.13 KiB) Viewed 1022 times
IMG_5649.jpg
IMG_5649.jpg (119.88 KiB) Viewed 1022 times
Paul. 1962 Series 1 roadster 850543
1965 mk 1 Lotus Cortina
1973 Triumph Stag (had it since 1982)

Link:
BBcode:
HTML:
Hide post links
Show post links


cactusman
Posts: 1919
Joined: Wed Nov 14, 2012 11:09 pm
Location: Hertfordshire
Great Britain

#3 Re: fuel & temp gauge reading to high.

Post by cactusman » Tue May 14, 2019 5:03 pm

If they both drift up it may be the voltage regulator. The traditional one switches the 12 volts On and off to provide an average 10 volts. To measure it you will need an analogue meter (an AVO meter is the best). Best thing is to replace with a modern electronic version....readily available or build your own....you need a low drop out 10 volt regulator chip....e.g. LM2940-10 plus a couple of capacitors...
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

Link:
BBcode:
HTML:
Hide post links
Show post links

User avatar

Topic author
Paul Jorgensen
Posts: 42
Joined: Wed Oct 26, 2016 7:28 am
Location: Southampton
Great Britain

#4 Re: fuel & temp gauge reading to high.

Post by Paul Jorgensen » Sun May 19, 2019 9:02 pm

Thank you for your reply cactusman, where cam
N I purchase one for a positive earth car
Paul. 1962 Series 1 roadster 850543
1965 mk 1 Lotus Cortina
1973 Triumph Stag (had it since 1982)

Link:
BBcode:
HTML:
Hide post links
Show post links


cactusman
Posts: 1919
Joined: Wed Nov 14, 2012 11:09 pm
Location: Hertfordshire
Great Britain

#5 Re: fuel & temp gauge reading to high.

Post by cactusman » Sun May 19, 2019 9:17 pm

Positive earth car..then the chip I suggested is no good. You will need a -10 volt low drop out regulator. They do exist but are rare...you need this one....
https://uk.rs-online.com/mobile/p/low-d ... s/1025700/

Lm2940T-10.0/NOBP. Both the input and output line need a 100 nF ceramic to ground. The output should also have a 10uF electrolytic capacitor to ground....

Do also be aware that the pin outs of negative regulators (needed in positive earth cars) differ.from positive regulators. The mounting tab is NOT connected to ground and they are more prone to instability if not appropriately bypassed with capacitors....do refer to the data sheet when connecting.
.
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

Link:
BBcode:
HTML:
Hide post links
Show post links

User avatar

Topic author
Paul Jorgensen
Posts: 42
Joined: Wed Oct 26, 2016 7:28 am
Location: Southampton
Great Britain

#6 Re: fuel & temp gauge reading to high.

Post by Paul Jorgensen » Tue May 21, 2019 1:03 pm

Thank you again for your reply, I have looked on the RS site and to be honest I am totally confused, would you be able to provide part numbers and maybe a diagram of how to make the unit.
Sorry to be a pain!!!
Cheers
Paul
Paul. 1962 Series 1 roadster 850543
1965 mk 1 Lotus Cortina
1973 Triumph Stag (had it since 1982)

Link:
BBcode:
HTML:
Hide post links
Show post links


Tony
Posts: 918
Joined: Mon Nov 02, 2009 2:12 pm
Location: UK
Great Britain

#7 Re: fuel & temp gauge reading to high.

Post by Tony » Wed May 22, 2019 6:50 am

I maybe barking up the wrong tree here but I had a similar problem and it was solved by replacing the old voltage stabilise behind the dash for a electronic voltage stabiliser from SNG, for a positive earth car which was quite cheap. May not be the same issue but it is a 5 minute job. Feel free to blow me out of the water if I am getting confused. One of our forum member did the job for me at Bicester a couple of years ago. Never had any problems since.
Tony (E typed)

Tony

Link:
BBcode:
HTML:
Hide post links
Show post links


cactusman
Posts: 1919
Joined: Wed Nov 14, 2012 11:09 pm
Location: Hertfordshire
Great Britain

#8 Re: fuel & temp gauge reading to high.

Post by cactusman » Thu May 23, 2019 3:56 pm

The SNG unit will fit just fine....it probably has the regulator I suggest within.....or it is a fairly easy job to scrape the mechanical innards out of your reg and fit the electronic components within....that's what I did....paul....pm me and I will do my best to send you the circuit diagram!
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

Link:
BBcode:
HTML:
Hide post links
Show post links

User avatar

JerryL770
Posts: 283
Joined: Sat Dec 09, 2017 2:58 pm
Location: Northants
Great Britain

#9 Re: fuel & temp gauge reading to high.

Post by JerryL770 » Mon May 27, 2019 2:51 pm

Do you have the part number for this improved version voltage stabiliser as SNGB parts catalogue for both S1 and S2 cars say part no: 148876J is no longer available and offers no alternative.
Jerome Lunt
1970 S2 FHC - Dark Blue, Red Interior, MX5 Seats

Link:
BBcode:
HTML:
Hide post links
Show post links


cactusman
Posts: 1919
Joined: Wed Nov 14, 2012 11:09 pm
Location: Hertfordshire
Great Britain

#10 Re: fuel & temp gauge reading to high.

Post by cactusman » Wed May 29, 2019 6:22 am

LM2940-10NOBP is the wrong part....bear with me.....Will get the correct one!!!
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

Link:
BBcode:
HTML:
Hide post links
Show post links

Post Reply Previous topicNext topic