oil temp sender help please...

MaSnaka · #1 (**permalink**) 08-18-2011, 09:37 PM

I have Stewart Warner guages and have been having trouble with a oil temp sender. Originally with a stock pan (390fe) the sender was installed into it's bung and I could read the temps on the gauge. I upgraded to a new pan (larger capacity) and installed a bung for the temp sender and the original sender never worked. I replaced that sender with a universal sender purchased through Summit and was getting readings again but they were all over the place, I could be sitting at a light idling and the reading would creep up to near 300F and then creep back down as I increase rpms and drive away. The readings would get pretty high with just normal driving. Anyway I purchased a new SW sender that is rated for the temps on the gauge (100-320) and I get nothing, put the universal one in while waiting for the replacement and it works, replacement comes and nothing. Anybody have an idea why? Should I keep returning the non functioning senders until one works? Is it normal to get bad senders? I ground the sender wire and the needle goes to the max. Thanks, John

Rick Parker · #2 (**permalink**) 08-19-2011, 12:35 AM

Temperature Senders - Stewart Warner

Be sure you have one for a single gauge??

strictlypersonl · #3 (**permalink**) 08-19-2011, 04:01 AM

Note that you must have good electrical contact between the sender and the pan, and the pan to the block. Sometimes sealer or Teflon tape prevents this.

acmjg · #4 (**permalink**) 08-19-2011, 05:53 AM

I'm having the same exact problem with mine. Replaced the sender with a brand new SW sender matched to the gauge and it will just barely come off of 140 degrees. Let me know what you find!!

jhv48 · #5 (**permalink**) 08-19-2011, 07:23 AM

Are you sure the sender is in constant contact with oil in the pan? Could be above the oil level or too high so that the sender gets uncovered during acceleration or cornering. Also, is the sender extending beyond the bung and in the oil. Some senders are so short that they don't extend beyond the bung in the pan, thus giving you an erroneous reading.

acmjg · #6 (**permalink**) 08-19-2011, 08:33 AM

Jim,

On mine everything you mentioned has been addressed. Unless it is at all possible my oil is only 145* but I doubt it. I'm going to block my oil cooler next time out and see what happens.

MaSnaka · #7 (**permalink**) 08-19-2011, 08:46 AM

Let's see where do I start...trying not to write a novel here. I don't use anything on the threads so there should be metal to metal contact there, I have the bung at the front bottom edge of pan, I have run new wire of greater gauge size to the gauge, scuffed the pan real good at one of the bolt locations, I have a sender that does send a signal just not calibrated for the specific gauge. Like acmjg the reading will just barely creep up to 140f and stop. I do not run an oil cooler. It seems like it could be a grounding (when in doubt check the ground) issue and I'll run a seperate jumper to eliminate that possibility.

lovehamr · #8 (**permalink**) 08-19-2011, 11:35 AM

Before you blow it off you might want to try an IR temp gun on the pan. That's how I found out that I had missmatched sender/gauges.

Steve

cdnus · #9 (**permalink**) 08-19-2011, 12:14 PM

Check the sender housing to ground with a ohm meter, should get a signal if properly grounded.
I took a pea soup can (cleaned up of course) silver soldered a fitting in the side. Fastened a ground wire to it, installed my oil temp sender in the fitting, sat the can on a small single element stove under the car, attached the gauge wire to the sender, checked everything for continuity, filled the can with water & turned on the heat,
When the water began to boil, checked the Gauge & it was 10deg. low. A little over 200.
Close enough, I checked my water temp. sender the same way.
Easy, cheap, accurate & quick, no guessing involved

Hope this is understandable & helpful

Craig

Tony Radford · #10 (**permalink**) 08-19-2011, 12:53 PM

My oil temp sensor never worked when it was installed in the oil pan. I moved it to the oil filter adapter (which is mounted horizontally) and everything works great. I'll bet it's not seeing a constantly solid contact with the oil.

Modena · #11 (**permalink**) 08-19-2011, 03:46 PM

Quote:

Originally Posted by cdnus

Check the sender housing to ground with a ohm meter, should get a signal if properly grounded.
I took a pea soup can (cleaned up of course) silver soldered a fitting in the side. Fastened a ground wire to it, installed my oil temp sender in the fitting, sat the can on a small single element stove under the car, attached the gauge wire to the sender, checked everything for continuity, filled the can with water & turned on the heat,
When the water began to boil, checked the Gauge & it was 10deg. low. A little over 200.
Close enough, I checked my water temp. sender the same way.
Easy, cheap, accurate & quick, no guessing involved

Hope this is understandable & helpful

Craig

top idea Craig!

MaSnaka · #12 (**permalink**) 08-19-2011, 09:06 PM

Thanks for all the help so far. Here is what Ive done. With the sender installed in the pan (cold) I checked with my ohm meter and have a reading (pegs about 3/4 on the ohm meter) between the sender wire and the ground. I took off the sender wire and there is a very low (just a slight bump of the needle) ohm signal between the wire connection and ground. When I use the heat gun to heat the sender the reading goes up so I assume the sender is not dead. I ran a seperate ground wire from one of the oil pan bolts to the engine block and now have zero resistance from the pan to the chassis ground. My oil pan was powder coated and with the gasket maybe there is too much resistance for a good ground. I'll give it a road test tomorrow and let you know what happens. Wish me luck.

Thanks,
John

MaSnaka · #13 (**permalink**) 08-20-2011, 05:36 PM

Well my road test revealed the same bad results as before. Sender is no good, it did get to just over 140f on the gauge. My ifra red gun revealed 195f on the exterior pan/sender location. I know there is a good ground, I know there is a good sender wire, I know there is a good gauge, I know there is no teflon or thread sealer, I know the sender is sitting in the oil at the bottom of the pan. I'll return this sender and try sender number 3. What a pain.

John

Gaz64 · #14 (**permalink**) 08-21-2011, 12:06 AM

John,

I'd say you have a mismatch of parts.

I have a resistance box 0-10000 ohms, of which I can dial up any figure in between.

If testing a gauge, I have the values necessary for the gauge test readings.

Having done that, I know where the fault will be.

Can you list the resistance values of your sender - cold and hot?

SF_SN888KE · #15 (**permalink**) 08-21-2011, 08:21 AM

Don't mean to hijack this thread since this relates to eletrical sender ... but

I have a similar problem using a mechanical 2-5/8" SW gauage and Canton 9qt oil pan on SB 347. Big thread fitting of mechanical sensor fits on left side of pan, probably 2" up from bottom of pan. Zero readings. Sensor will not fit oil plug threads at front of pan. (gauage did move off the bottom once or twice - but usually zero)

Thinking of putting new bung at back of pan or using an oil filter sandwitch to get a more accurate reading. Anyone use a sandwitch and temp sensor without adding an oil cooler or remote oil filter? Seems like a big expense to get the oil temp gauage to work. (did that on my other cobra using Earl remote, temp block, etc)

Not worried about the oil temp as the engine runs at 180-190, even in heavy traffic and I don't track the car. just bugs me.

MaSnaka · #16 (**permalink**) 08-21-2011, 10:53 AM

Gaz64 do you know what the ohm values should be on the sender for a 140f-320f gauge 12v? In the mean time I will get a reading.

thanks,
John

Dwight · #17 (**permalink**) 08-21-2011, 11:06 AM

I , like Tony, did not get a good reading when the sender was in the oil pan. I moved it to the remote adapter and now I get a correct reading when I check it with my IR gun.
I had the same problem with the GT 40. Moved the sender and problem solved.

Dwight

MaSnaka · #18 (**permalink**) 08-21-2011, 03:42 PM

Dwight,
I have my oil pressure hooked up to the remote adaptor. As far as I can see there is only one port that I can get to.

Thanks
John

MaSnaka · #19 (**permalink**) 08-21-2011, 09:26 PM

Gaz64,I took some ohm readings and this is how they turned out. This is with the sender on a bench one probe on the wire stud and the other probe on the part of the sender that would be in the oil pan. BTW I used a heat gun to heat the sensor and then used an infrared gun to measure the temp.

Cold 72F 8.42
hot 212F 107
super hot 300F 70

I would think super hot would have a higher value.
Let me know what you think.

Thanks,
John

Gaz64 · #20 (**permalink**) 08-22-2011, 03:12 AM

Quote:

Originally Posted by MaSnaka

Gaz64,I took some ohm readings and this is how they turned out. This is with the sender on a bench one probe on the wire stud and the other probe on the part of the sender that would be in the oil pan. BTW I used a heat gun to heat the sensor and then used an infrared gun to measure the temp.

Cold 72F 8.42
hot 212F 107
super hot 300F 70

I would think super hot would have a higher value.
Let me know what you think.

Thanks,
John

John,

Can you re-clarify your readings please?

Your reading of 8.42, is this ohms or Kohms?

Typical temp senders are all NTC - negative temperature coefficient, meaning as temp increases, resistance decreases.

PTC is temp increase, resistance increase - just like any normal metal, steel, copper etc.