Speaking of oil temps

[casaleenie]

Someone explain to me how the oil temps are read and transmitted to the guage. My doesn't work and since I've had the car it never has.
It's a remote oil filter with the wire coming out of the top of the filter.
What should I look for to repair it??

thanks

AL

[clayfoushee]

Al,

Mine's on the oil pan, and it barely registers anything. Haven't gotten a good answer in 6 months of searching, except try replacing the gauge. I'm not an SW fan. My tach. sticks too, but if I tap on it long enough it unsticks.

Clay

'98 Unique #9299, 427FE side oiler, top-loader (close), 3.31 rear

Annapolis, MD

[GeorgiaSnake]

Al it's magic - you just need to move little squares with railroad tracks on them. Once you get them right the little train will take you to the right place [}:)]

Randy


Unique 289 FIA
Southern Automotive 396
Team III 16's
Brilliant Silver

[pgermond]

Mine is mechanical (uses the same type sending unit as the water temp) and comes out of the Canton pan. I have Autometer gauges and, while I don't want to get into a discussion like the one that is going on over on "Overheating", these gauges appear to be dead-on. They all work (none were DOA) and they look reeeal good [^]

Phil

427 Roadster, #4279436
Southern Automotive FE
3:31 and Toploader

Roseville (N.Cal)

[WBofTN]

Clay:
I replaced my oil temp guage b/c it was NOT moving[xx(]. Guess what? new guage does NOT move either:(. My Oil temp sensor is located in the bottom of my pan. So I kinda give up and presume my oil is nice
and cool[8D].
WB

'93 Unique 427/351W/4sp

[gasman]

Mine doesn't work either.

Steve Foushee

[GeorgiaSnake]

Mine works great - depending on the conditions I see 190 to 210 degress while driving. You guys with the defective gauges may have boken lines. The unit will not send a signal to the gauge if the continuity is broken. Try putting the probe on boiling water or put some heat to it with a propane torch. Mine is the optional SW supplied by Unique.

Randy

Unique 289 FIA
Southern Automotive 396
Team III 16's
Brilliant Silver

[Silk]

Mine also taps into the remote oil filter and reads about the same as Randy's - 190-210, and slightly higher on the track and lower in winter. SW guage. Seems to work fine.

Gary
Unique FIA 351W

[jhaynie]

Mine works but I disconnected the wire a few months ago redoing some of harness, and never reran it to the oil filter. Couldn't decide on a good place to hide it.

John

[Brent]

If it is a single wire sending unit the "ground" comes from what the unit is threaded into. If there is thread tape or sealer on the threads that can disrupt the ground. If the remote cooler is not grounded that can also be the problem.

Brent

[clayfoushee]

OK....so we're about 50/50 on the reliability of SW gauges, but that's hardly a resounding testimonial to their quality is it? In my line of work, we like to see numbers like 99.99999999% reliable.

Clay

'98 Unique #9299, 427FE side oiler, top-loader (close), 3.31 rear

Annapolis, MD

[excelguru]

Time for some schoolin'...

In general, temperature sender units are either RTD (resistance), liquid expansion, or bi-metal types.

RTD's usually involve a platinum sensor and two wires coming back to a measuring device. The electrical resistance of platinum (or all metals for that matter) changes as the temperature changes (low temps = less resistance). This change in resistance is measured and converted to a temperature reading. This obviously involves electronics, so if your gauge doesn't have an electrical source running to it (with the exception of the light) then it's not an RTD type.

Liquid expansion types are much more mechanical and are most likely the types that we have on our cars. Basically, the sensor "bulb" will contain a liquid (usually water mixed with something). An armored capillary (filled with the same liquid) will extend from this bulb to a gauge device. As the liquid heats, it expands. This expansion is transferred through the capillary to an armature which in turn actuates the needle on the dial. All mechanical. No electricity. It can be very reliable so long as the armored cable doesn't get damaged. One tiny leak in the cable and it's useless.

The last type would be a bi-metal device similar to the old-style thermostats in your house. Two dissimilar metals are bonded together. The two metals expand and contract at different rates with changes in temperature. This causes the bi-metal strip to bend (or straighten). This movement is then transferred to an indicating device similar to the armature mentioned above. I would be stunned if any of our cars had this type of device.

I agree with Clay. If my employer's reliability numbers were 50%, we would be closing our doors soon.

Keith :)
Unique Motorcars (http://www.uniquecobrareplicas.com)
Southern Automotive (http://www.southernautomotiveengines.com)
Bruce Bunn (the painter) (http://www.jodecoautobody.com)

My Photo Album (http://members5.clubphoto.com/keith355593/owner-429c-1.phtml)

[jhaynie]

See what I said about here come the engineers?? (see overheating thread).;)

[gasman]

John, I think we all have time for a part time job. ;) This website would have it all if we could get meds on line and mortgage our houses.. [:o)]

Steve Foushee

[Jim Harding]

Keith has explained the electrical gauge almost right;)

From my notes on SW electrical oil temp gauge probe:

At 140 degrees, the probe will be approximately 1000 ohms.

At 200 degrees, the probe will measure about 475 ohms.

At 230 degress, the probe will measure about 300 ohms.

In electrical circuits there exists "OHMS LAW", which simply stated says, circuit current is equal to the voltage divided by the resistance. With our electrical gauges, the oil or water temperature changes the resistance of the probe, which changes the circuit current, and this current is measured by the dashboard gauge, which has a scale calibrated in degrees rather than amps (or milliamps).



Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[Jim Harding]

Al,

To check your electrical temp gauge.......

If you have a volt/ohm meter, measure the voltage (with the ignition on) at the terminal on the temperature probe. Make sure the negative lead of the meter is connected to battery negative, or a good frame ground.

The voltage should be something slightly LESS than battery voltage if the circuit is properly hooked up.

If the voltage is zero, you have an open circuit somewhere, i.e. no 12 volt connection at the gauge, bad gauge, or an open circuit (broken wire?) between the gauge and the probe.

If the voltage is exactly the same as battery voltage, the probe is either bad or threaded into a non-grounded object. To check, hook up a temporary jumper wire from the engine block to the threaded part of the probe and recheck the voltage.

To check the gauge and associated wiring, have someone observe the gauge while you QUICKLY short the probe lead to ground and remove it. If all is right, the gauge needle will swing all the way to max temp very quickly..... so don't leave the short on the wire too long or you'll damage the gauge.



Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[casaleenie]

quote:Originally posted by GeorgiaSnake

Al it's magic - you just need to move little squares with railroad tracks on them. Once you get them right the little train will take you to the right place [}:)]

Randy


Randys still upset with the railroad thing...
You guys can have a go at it also...

And thanks for all the info.. I'll have it up and running tonight...


http://www.railroadtycoon3.com/rt3/us/downloads/game.html



Unique 289 FIA
Southern Automotive 396
Team III 16's
Brilliant Silver



AL

[Tony Radford]

When I purchased my car, the oil temp sending unit was installed in the dip stick location of my Canton pan. I never registered. I moved it to the plug hole in the end of the remote oil filter bracket and it works great. I'm running the SW gauges. I did replace the gauge with the lower range unit (same range as the water temp gauge). It runs 190-230 degrees consistently.

427SC, Torch Red / white stripes
427 Windsor Stroker from Southern Automotive
Delicious example of Beauty + Power.

[Mike Geddes]

Maybe I don't drive my car as hard as some of you guys, or maybe it's just that the ambient temp. here in Canada is a bit lower than
some of your locations.
I ran my car for over 5 years before I actually saw a reading on
the oil temp. gauge.....and then it only just moved off the low end
of the range....I believe the SW gauge starts at 140 degree's F.
( I haven't seen my car for 6 months...in winter storge.)
I have the oil temp sensor in the base of the oil pan.
Mike

Mike Geddes

[Jim Harding]

I meant to mention this earlier.....

My oil temp probe is also located low in my cast aluminum oil pan. Very seldom did it ever move unless I was sitting still for a long period. A guy in our local club suggested that I insulate the probe with tin foil. So I loosly wrapped a half dozen wraps around the probe and the capulary (sp) tube. Now it tracks along with the water temp gauge most of the time, and reads something higher if I hammer it while going down the interstate. My guess is that the probe was being cooled by the air flow over it. For you guys with electrical gauges that want to try this trick, first cover the wire terminal with electrical tape so you don't short it out.

- Jim -

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[spd4me]

While were on the topic of gauges, all mine work great except for the Amp gauge. It doesn't move at all. When I first wired the car the instructions said not to hook up blue wire to orange wire at alternator. Gauge didn't work. So I hooked up blue to orange and when I reved engine the gauge needle moved to the negative side. I asked Alan Weaver about it and he said to reverse the wires on the rear terminals which I did and now it doesn't move. Now it any of you have an answer please be advised I'm a simple minded person.

[Mike Geddes]

I had the same conversation with Alan 10 years ago.
The same thing happened....the ammeter went negative.
Changed the wires back and have not bothered with it since.
Mike

Mike Geddes

[Jim Harding]

The below diagram is for an ammeter that reads total circuit current. There is also an ammeter that is refered to as a "shunt" type, where the shunt passes 99 percent of the current and the meter is wired in parallel with the shunt and only passes a fraction of the current. The diagram is generic and should work for most direct reading ammeters.

http://www.uniquecobra.com/uploaded/Jim Harding/AMMETER.JPG

The lead marked "to fuses" should supply 12 volts to every electrical device on the vehicle except the starter motor. If the gauge indicates "backward" movement, reverse the wires from one terminal to the other, keeping the alternator and fuse leads together.

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[spd4me]

Jim
Thanks for the diagram. I'll check it with the wiring manual I got with the car.

[WBofTN]

Jim:
your expertise is once agian needed.
I put a meter on my oil temp probe terminal yesterday (grounded to the frame).
Results: big fat 0 with the key on, but with the key off I get a 11.xxx reading.
So is something wired wrong?? Sorry - I'm electrically challenged.
Wes

'93 Unique 427/351W/4sp

[eliminator]

WB,

Have you got a good ground strap from the motor to your frame?

Rick

[WBofTN]

I don't know Rick. I never noticed a strap. What setup to you have??
Wes

'93 Unique 427/351W/4sp

[Jim Harding]

WB

Were you using a volt meter? If so, the readings are backwards from what you should see!!!

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[WBofTN]

Jim:
I'm using a volt/ohm meter set on continuity to get that reading.
I got no readinga set other settings
Wes

'93 Unique 427/351W/4sp

[Jim Harding]

Wes,

I guess you tried the procedure I described earlier in this post - "To check your electrical temp
gauge" -

Stick with me here, because I'm going to give you some simple steps to locate the problem. If you cannot understand the theory or the results of the tests, that's fine..... just try to give me the answers to each step, and between the two of us we'll get to the bottom of the problem.

I guess it's time to stick your head under the dash.....

But first, disconnect the wire to the temp probe and make sure it is not touching ground (or anything else for that matter)

On the back side of the gauge, there should be two terminals (three if you count ground).

One lead should have 12 volts on it. Voltage supplied from the ignition switch in the "RUN" position.

The other terminal should have a wire on it that runs to the temp probe.

Locate a good ground point under the dash and connect your VOLTMETER negative lead there. Do not use the case ground of the gauges, but try to connect to the frame if possible. To make sure you have a good ground point, touch the positive probe to something with 12 volts on it.... like a terminal of the ignition switch. (one of them WILL have 12 volts on it) If all is good at this point, try the steps below........

Turn the key to RUN (you don't have to start the engine)

Touch the positive lead of the VOLTMETER to each terminal on the gauge. (be careful and not short these terminals to the case of the meter or other ground.) They both should have 12 volts on them.

If neither terminal has 12 volts, you have a problem between the ignition switch and the gauge.

If only one terminal has 12 volts on it, the gauge is bad.

If both terminals have 12 volts on them, place the positive lead of the voltmeter on the gauge case (ground). You should not see any voltage here, but if you do, this means the gauge is not grounded.

If both terminals have 12 volts on them, and the case does not, check the terminal at the temp probe. It should have 12 volts on it. If it doesn't, there is a problem between the gauge terminal and the probe terminal.

If the 12 volts is present on the terminal, re-connect it to the temp probe.

The voltage should still be there, albeit a tad lower than when it was not connected.

If the voltage is still present, move the positive lead of the voltmeter to the threaded part of the temp probe that connects to the engine/filter/cooler/whatever.

There should be no voltage here........ if there is, this means the probe is not grounded to the frame/engine.

Also, get back under the dash again and check the voltage on the gauge case agian..... it should still be zero.

Turn off the ignition switch.

If all the tests up to this point have been normal, disconnect the wire at the temp probe again. Switch your meter to measure ohms, and connect the leads of the meter to the probe terminal and frame ground..... you should measure something, a thousand ohms or more if the probe is good.

If you measure infinity, this means the probe is bad.

Let me know what you find..... I hate to be long winded here, but after this, we WILL know where the problem is.

- Jim -

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[WBofTN]

Thanks Jim: You have gone above the call of duty, and its much welcomed.
I will print out your directions and attempt to pinpoint the problem one
night this week.
Wes

'93 Unique 427/351W/4sp

[Tony Radford]

Wes, I think you'll find out that your sensor is in a bad location. That sensor probe needs to be submerged in oil all the time. When mine was in the pan, it never read anything at all. My remote oil filter bracket is mounted so that the filter is horizontal with the sensor mounted in the hole opposite the filter. It starts reading shortly after the water temp gauge starts working. My oil temp is consistently 30-60 degrees hotter than the water. I replaced my original SW oil temp gauge with a lower temp unit for better resolution (it has the same temp range as the water temp gauge).

427SC, Torch Red / white stripes
427 Windsor Stroker from Southern Automotive
Delicious example of Beauty + Power.

[clayfoushee]

Tony, I tend to think you're right based upon my experience. Mine is on the oil pan drain plug and doesn't read at all, even with the oil cooler blocked off by a panel I made.

Clay

'98 Unique #9299, 427FE side oiler, top-loader (close), 3.31 rear

Annapolis, MD

[Tony Radford]

Clay, every time my oil temps hits 230 (highway cruising) I'm glad I've got an oil cooler. You need to unblock that cooler and move your sensor. I've been told that SBs don't need a cooler, but I'm glad I have mine.

427SC, Torch Red / white stripes
427 Windsor Stroker from Southern Automotive
Delicious example of Beauty + Power.

[clayfoushee]

Tony, you're right. I don't leave it on when it's hot, or when I'm on an extended drive. It's attached with velcro, but one of these days I'll get around to moving the sensor.

Clay

'98 Unique #9299, 427FE side oiler, top-loader (close), 3.31 rear

Annapolis, MD

[WBofTN]

Hey Jim:
I did alot of metering last night. Thanks to your punch list.
I'm getting 12v to all the right places.
The problem seems to be the probe.
I get no continuity from the threaded portion of the probe to any other
ground (even the nut that holds the probe in place.)
So, I assume its been taped (unless you tell me otherwise).
I'll have to wait untill oil-change time to check this out (probe in the bottom of my pan).
Again thanks for your time and efforts.
Wes


'93 Unique 427/351W/4sp

[Jim Harding]

Wes,

Your assumption seems logical. Did you happen to check continuity from the pan to engine block/frame? That would put it problem firmly between the threads of the probe and the pan.

You could run a jumper wire from the block/frame to the threaded part of the probe and maybe hold it in place with a small hose clamp. If it works, then you can pull the probe and stick it back in properly.

- Jim -

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[WBofTN]

Jim:
I did not check continuity from the pan to the block, but did check it from the pan to the frame (no continuity).
I thought a/b that jumper wire ground, but talk self out of it. Maybe I will try that this weekend.
Thanks Wes

'93 Unique 427/351W/4sp

[Jim Harding]

quote:Originally posted by WBofTN

Jim:
I did not check continuity from the pan to the block, but did check it from the pan to the frame (no continuity).
I thought a/b that jumper wire ground, but talk self out of it. Maybe I will try that this weekend.
Thanks Wes

'93 Unique 427/351W/4sp


Unless the pan is plastic, the odds of this condition is rather rare;)

We can be sure the block is grounded to the frame, because the starter motor (which draws gobs of curent) works. So even with a dozen bolts holding the pan to the block, you would think that at least one would make a good electrical connection[?]

Good luck with this Wes, and let me know how it turns out.

- Jim -

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg