 Oil Temp Gauge, Testing question |
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| jim_hoyland |
 Apr 26 2015, 04:51 PM
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#1
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Get that VIN ?  Group: Members Posts: 9,306 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California 
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If the wire from the oil temp gauge is disconnected from the sender and grounded to the chassis, should this cause the gauge to read a maximum temp ? I assume that as oil gets hotter, resistance is reduced activating the needle in the gauge ?
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Replies(1 - 7)
| Dave_Darling |
Apr 26 2015, 09:48 PM
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#2
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914 Idiot Group: Members Posts: 14,990 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
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I believe that is how it works. I know that when I smashed my temp sender wire (between the motor mount bracket and the mount, I think) the gauge pegged full hot. Scared the crap out of me at first.
--DD |
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| era vulgaris |
Apr 27 2015, 07:37 AM
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#3
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J is for Genius Group: Members Posts: 982 Joined: 10-November 13 From: Raleigh, NC Member No.: 16,629 Region Association: South East States |
I'm also trying to troubleshoot my incorrect-reading oil temp gauge. Except mine is on the opposite end in that it's reading too low.
If the sender fails does it typically read too low or does it short to ground and read too high? |
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| jim_hoyland |
Apr 27 2015, 09:19 AM
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#4
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Get that VIN ? Group: Members Posts: 9,306 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California
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QUOTE(era vulgaris @ Apr 27 2015, 06:37 AM)  I'm also trying to troubleshoot my incorrect-reading oil temp gauge. Except mine is on the opposite end in that it's reading too low. If the sender fails does it typically read too low or does it short to ground and read too high? I haven't had a sender fail on me. It's important to match the senders max temp to your gauge. The best way I found to determine what the sender is doing is to remove it from the engine and submerge it in boiling water- a known temperature. IIRC, you will have to ground the sender to chassis while doing this; that is because the sender reduces resistance as it get hotter. Check the sender. There is a temp marked on the hex part |
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| stugray |
Apr 27 2015, 10:02 AM
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#5
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Advanced Member Group: Members Posts: 3,824 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
These temp sensors are Negative Coefficient Thermistors.
The resistance goes down as the temperature goes up. They approach a dead short as the oil temp exceeds 300 degrees (IIRC). So yes, shorting the wire should peg the meter to the Hot side. |
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| timothy_nd28 |
Apr 27 2015, 11:43 AM
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#6
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Advanced Member Group: Members Posts: 2,299 Joined: 25-September 07 From: IN Member No.: 8,154 Region Association: Upper MidWest
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| 76-914 |
Apr 27 2015, 12:37 PM
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#7
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,504 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California
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Be sure your sender matches the gage.
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| malcolm2 |
Apr 27 2015, 01:43 PM
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#8
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Advanced Member Group: Members Posts: 2,745 Joined: 31-May 11 From: Nashville Member No.: 13,139 Region Association: South East States
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If you can take the gauge to the kitchen it is easier. I used a 12v battery from my drill and a few wires and aligator clips. Get a wire to hang the sensor in the pan of water so it is only touching water.
If you look closely at the outside edge of the gauge you will see #s to help you. Stick a meat thermo in the water set on *C and compare. I'll see if I can find my post with pictures. FOUND IT That thread is good for testing only. We did not fix anything by adding a POT, ignore that part. I ended up getting new gauge guts, but have not gotten my taco plate etc... coming from across the pond. I'll re-try to fix at my next oil change. |
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