oil temp gauge wiring.

[tvr383 0]

Hi,

On my 1973 18-auto there is an oil temp. and I think I have wired it wrong as it sticks to maximum even when starting the engine.There are two prongs identified as L and 2 plus one unidentified in the center.actually I have one from the sensor on one of the side,one from the switch (+ I guess) on the opposite side one and nothing in the centre.

Any suggestions?

thanks.

[Save Old Iron 1,571]

Any pics of the back of the gauge to show the terminals and the designations on the terminals ??

The gauge will need a ground, +12v connection and sender connection. The "L" may be for the illumination light inside the gauge. Just a guess.

A picture would help.

[pfrederi 18,638]

I have spent a fair amount of time on D series gages as of late....

Having 3 terminals on the back of the gage indicates to me it is not an original gage...the ones i have seen only have two terminals. It sounds like you have it wired correctly (have you tried reversing the wires???)

Does your Oil pressure gage work correctly? It shares a power source with the temp gage.

The sending unit is a variable resistor with resistance dropping as it gets hot. If your gage is pegging then I would suspect you have a faulty sending unit or a short.

Do you have a digital multimeter???

If so check the gage to sending unit for a possible short.

Check for resistance from the terminal lug on the unit to the pump housing. It should not be zero. If Zero sensor is bad. Next pull the sensor unit and establish a base line resistance reading. Then put the unit in some hot water and take another resistance reading it should have declined. (I forgot what the readings were on the original units if you get this far ask again and i will test one of mine.)

If the sending unit checks out OK and the oil pressure gage works OK then we can be pretty sure your gage itself has died.

OR for about $17 you can buy an after market gage and sending unit and replace the whole setup....

If you want original WH stuff bend over and prepare to pay big time....

[Save Old Iron 1,571]

Paul,

on the original D series temp gauge - with 2 terminals - is the ground connection established thru the gauge case / gauge bracket to the chassis ? If so, that would leave the other two terminals for the +12 volt power and sender connection.

Thanks

[pfrederi 18,638]

There is no need to ground the gage body itself (except for illumination purposes).

The sending unit is the ground ... albeit a variable one.

[Save Old Iron 1,571]

True, the sender body is grounded, but that does not supply a ground to the gauge body.

There is much evidence and documentation to support the need for a ground to an electric gauge.

Going back a step or so, we need to clarify what style gauge we are discussing - older bimetal based gauge or newer electromagnetic gauge.

Some very old style gauges (around 1960's and earlier) work off a bimetallic heating element inside the gauge body and do not require a gauge "ground". As you stated above - an increase in temperature at the sensor lowers the sender resistance and allows higher current flow thru the sender wire - increased current flow causes a bi-metal element inside the temp gauge to heat and "flex" and push the gauge pointer to a different temperature readout.

For the current breed of electric gauges (after 1970's) most operate on electromagnetic deflection of the pointer needle versus mechanical movement by heating.

Per instructions from SUN gauges, At least three electrical connections are needed for a "modern day" electromagnetic gauge.

Another caution on the sender grounding issue - DO NOT wrap the sender threads with Teflon tape to help prevent leaks at the sender. The Teflon tape will act as electrical insulation and will cause the gauge to operate improperly.

Here's a guide - hopefully its helps

Again, I do not own a D series - never worked on one - so take it for what its worth.

[pfrederi 18,638]

What you say makes sense for newer gages. The original WH gage only had two terminals and both have fibre insulating washers to keep them from contacting the gage case and nylon inserts in the bracket for insulation.

In looking at the new Sunpro gage I am using it has three terminals. All three have insulators to keep the mounting bracket from touching the terminal studs. I am not using the ground terminal and the gage works...I don't know why.... but i will hook up a ground and see what if anything changes

[Save Old Iron 1,571]

Good suggestions Paul,

you have given 2 additional items to check on the gauge issue - fibre insulation washers on the gauge bracket and the gauge bracket is housed in what appears to be an insulated shroud. (pictures always worth a thousand words !!).

My guess is this is a thermally activated gauge.

Hope this link works - it shows the difference between the two style gauges and explains how they differ in operation.

http://books.google.com/books?id=UiYDAAAAM...page&q=&f=false

Thank goodness for a a copy of Popular Science from 1959. I knew those bi metal gauges where old. I probably would not trust the well being of my tractors to a gauge that old. Like you said - spend the $20 on a new gauge.

tvr383 -

let us know if your making any progress - It would help to know if the gauge normally goes to full scale if you shut the ignition off, Some gauges power off to full scale - others will go to their lowest reading.

Another method to troubleshoot this issue could be to disconnect wire from the sender - place the multimeter in series with the wire and sender to measure the CURRENT flowing thru the sender to the gauge. It appears you have a two terminal THERMALLY ACTIVATED gauge. You should set your meter to read AMPS - you should see the amperage thru the multimeter increase as the engine oil warms up. You should see some current flow even with the engine cold but the ignition on. Current should increase as the engine warms. If you see no current flow at all - check wiring continuity from sender to gauge and from gauge to +12 volts.

If wiring checks good, measure the ohms thru the sender (wire disconnected) as the engine heats - you should see the ohms drop as the oil heats.

This may save you from taking the sender out of the engine block.

Not sure if you have a multimeter or have experience measuring current with one - if you need help with that - let us know.

[Save Old Iron 1,571]

tvr383,

how did your temp gauge issue work out ??

any updates ??

:scratchead:

[tvr383 0]

tvr383,

how did your temp gauge issue work out ??

any updates ??

Hi,

Sorry I got busy salmon fishing the last three days and that's all I did...no tractor time at all.I have some pictures of the guage but can't upload them too large size they are.

Now some corrections are needed here...there are only TWO connectors behind the guage...what I thought was a third connector is simply a kind of small cmetal tag that applies some pressure against the dash backside where the guage mounts onto...why that is there I am not sure but could it be for grounding purpose?

The two terminals are marked as follow: L on the right hand side of guage as seen mounted into the dash,driver sat in place.And the number2 on the left hand side .

The two obviously available wire for this are: a yellow from the switch and a red from the sender...I had these as following until now: yellow from switch at left (that would be the positive) and the red from sender at right.

This combination was giving me an immediate max reading right upon switch on.

Today I have reversed the wires: left to right...did not tried it as I am busy working on the mower deck...another brainbreaking thing!

see what you think,

thanks.

[Duff 206]

Sorry I got busy salmon fishing the last three days and that's all I did...no tractor time at all.

Sorry to go for a moment, but where are you located? Is this a Fall salmon run? Are you a commercial fisherman or just for sport?

Duff :hide:

[tvr383 0]

Sorry to go for a moment, but where are you located? Is this a Fall salmon run? Are you a commercial fisherman or just for sport?

Duff

Hi Duff,

I am in Gasp

[Duff 206]

I've been around the Gaspe peninsula with my family - gorgeous country! Best of luck in your fishing!

(Now back to our tractors.......)

Cheers!

Duff :scratchead:

[tvr383 0]

It works now.Lacked of grounding as the new paint gave no contact to the bracket holding it in place .My gauge is of the 70 era and is a Faria.

thanks to all.

[Save Old Iron 1,571]

Ron ,

glad this worked out for you - good troubleshooting hint for those who are repainting their tractors

Make sure you maintain good ground connections.

:scratchead:

[Save Old Iron 1,571]

Paul,

on the original D series temp gauge - with 2 terminals - is the ground connection established thru the gauge case / gauge bracket to the chassis ? If so, that would leave the other two terminals for the +12 volt power and sender connection.

Thanks

Ron,

this is a link to the Faria webite for the temp gauge - it does show the the connections "S" for signal and "I" for ignition.

http://faria-instruments.com/site_manuals/IS0002F.pdf

If this represents your gauge correctly, you may want to establish a wired ground connection and not depend just on the bracket to establish a ground connection.

Thanks for the update.

[tvr383 0]

[tvr383 0]

Just another pic of it seen frontwards.

Attached Image

[Save Old Iron 1,571]

Ron, how is this gauge secured into the dash ?

Is it just a friction fit or is there a bracket that attaches to the gauge ?

You have identified the problem as a lack of a ground connection but now we need to worry about maintaining that good ground connection.

Great job on troubleshooting this issue and thanks for the update. Its always great to see what finally fixes the issue.

:scratchead:

[tvr383 0]

Ron, how is this gauge secured into the dash ?

Is it just a friction fit or is there a bracket that attaches to the gauge ?

You have identified the problem as a lack of a ground connection but now we need to worry about maintaining that good ground connection.

Great job on troubleshooting this issue and thanks for the update. Its always great to see what finally fixes the issue.

It holds in place by a small bracket,u-shaped,that has two holes a bit larger thant the two threaded bolting behind the guage wich bolting goes through these two holes into the u bracket.The bolting has insulated grommets around them so no grounding possible there. But attached to the u bracket there is a small metal tab that ,when bolting it down, will contact the guage body hence grounding it....eventually I could weld a wire to this tab and ground it better but actually it appears OK.

Thanks for the help,now I can pursue my task of adapting a Vulgar but solid believe me sears mowing deck to it!

[Trouty56 567]

The oil temerature gauge on my D-180 has/had the same problem. It is the same gauge as tvr383's. I was taking it in and out trying toget it to work and the dang needle broke. So being curious I took it apart. It is a magnetic gauge.

It was mentioned that an aftermarket replacement could be bought. I was looking for some but they all look like an interior gauge. Could you point me in the right direction as to where to purchase the replacement please. I was thinking of stopping at the local TSC and checking them out.

Thanks for any help.

Trouty

[Save Old Iron 1,571]

Trouty,

A marine gauge maybe a better bet for your application. Marine gauges are designed to operate in a much harsher environment than auto gauges. Water, vibration, and exposure to temperature extremes can play havoc with a cheap gauge meant for internal mounting on an auto.

A possible challenge will be getting the replacement gauge to read correctly with the D's electrical sender unit. Maybe if you check the current gauge - and it is manufactured by FARIA - check their website listed in this post. They may have a direct drop in replacement.

:scratchead: