Oil pressure gauge works intermittently. - Vintage Mustang Forums
 
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post #1 of 4 (permalink) Old 03-20-2016, 06:44 PM Thread Starter
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Oil pressure gauge works intermittently.

65 GT style gauges. I accidentally shorted the IVR a few weeks ago. Decided to try my hand at making one. Gauges worked fine at first but the oil pressure gauge started working intermittently and eventually quit working. Went back to a repop Ford style IVR, replaced the gauge and sending unit. The new gauge worked for about 10 minutes and quit. The other gauges seem to be working but the temp gauge seems to be moving around quite a bit and I dont trust it at this point. The ground for the instruments seems fine. I'm out of ideas.


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post #2 of 4 (permalink) Old 03-20-2016, 09:16 PM
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Originally Posted by MedievaL View Post
65 GT style gauges. I accidentally shorted the IVR a few weeks ago. Decided to try my hand at making one. Gauges worked fine at first but the oil pressure gauge started working intermittently and eventually quit working. Went back to a repop Ford style IVR, replaced the gauge and sending unit. The new gauge worked for about 10 minutes and quit. The other gauges seem to be working but the temp gauge seems to be moving around quite a bit and I dont trust it at this point. The ground for the instruments seems fine. I'm out of ideas.
Few yr. back I chased a similar problem with the oil press gauge. All tests said the gauge was fine. Went to a solid state IVR from Ebay and still no better gauge action. As a last ditch effort I bought a new gauge and all has been fine ever since. YMMV.

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post #3 of 4 (permalink) Old 03-21-2016, 01:39 PM Thread Starter
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Few yr. back I chased a similar problem with the oil press gauge. All tests said the gauge was fine. Went to a solid state IVR from Ebay and still no better gauge action. As a last ditch effort I bought a new gauge and all has been fine ever since. YMMV.
I replaced the gauge, sending unit, and IVR.


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post #4 of 4 (permalink) Old 03-21-2016, 08:27 PM
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Originally Posted by MedievaL View Post
I replaced the gauge, sending unit, and IVR.
You still could have a bad component in there. Ans since you had a short you could have damaged a wire which can cause all kinds of intermittent issues.

Ford gauge circuits were not not rocket science. The gauges operate on ~5VDC produced by the stock IVR 'pulsing' between 0 and battery voltage. The oil, temp, and fuel senders basically are all are variable resistors that go from 10 ohms (High OP/Temp/Fuel) to 73 ohms (Low OP/Temp/Fuel). The guages are fed 5V from the IVR on one side and are connected to their variable resistance senders on the other. The gauges are not -and should not be- grounded but the IVR must be well grounded to operate. If the IVR is bad then ALL gauges will have problems. If only one gauge is having issues (or, conversely, only one gauge is operating normally) the problem is NOT the IVR.

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