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I've seen plenty of articles about this and they all say you need a double-winding gauge core to make the mod happen, but never pictures to go with it.
I've had the true pressure gauge in place for a while now and am to the point of making the gauge show proper pressure. I pulled what appears to be a double-core gauge core from a 1990 w/o tach. It has two full windings and all that, but also a full four pins on the back. My instrument cluster only has opening for a three-pin gauge. Do I need to get the entire cluster, just the cluster panel and gauge core, or is there more info I'm missing here? I'd like to keep my PCM and the tach, obviously.
I don’t know what you read but you lost me. I converted the oil pressure gauge in my ‘89 by replacing the pressure switch on the engine with a real sending unit from an ‘87. Then bypassed the resistor on the back of the cluster. Done
EDIT: You have “stock ‘94 w/tach” in the picture so is that what year truck you are working on? I found this in a related thread
Yes, mine is the 94 with tachometer. I have also already bypassed the resistor behind the gauge, but my gauge still only went halfway. Like the rest of the posts i've seen, that one mentions just swapping the innards of the gauge. I'm just not seeing how that's possible with my cluster since mine only has three connections for the oil gauge and the dual-coil assembly has four pins.
I'll see if I can find a 92-93 cluster. From what I've read it sounded like you could use a gauge coil from as far back as the late '80's. Maybe that's not true here.
So basically, I learned this mod is completely useless, in my case, as the OE gauge doesn't begin to move until 40 psi.
So if my engine was having pressure issues, related to lower rpm/psi, I would never know it, unless those issues shown up in the higher range/psi, which isn't always the case.
So basically this takes you from a dummy gauge will a below 7psi warning light, to a slightly more intelligent dummy gauge, that retains a below 7 psi warning light.
I guess my two cents would be, go mechanical or nothing at all, this mod is pointless.
Unless aperson is bored watching their tach~speedometer move and wants a new gauge to move around in an erratic pointless way.
I can only attest that a proper pressure sending unit on a 5.0 in a 1994 run through a stock gauge after bypassing the resister only goes to half scale. Other than that, I cannot confirm or deny anything else. There aren't any 92-93 F150/250/etc in the local yards, so it could be a while before I can continue this. Wonder if these gauges might've also been used in cars?
Just read wwhite's comment. I can also say that the gauge is quite erratic in the half-scale that it uses. I thought that might just be the gauge itself trying to cram full-scale info into a half-scale movement.
My current understanding from comments in this thread is that I need to try a dual-winding gauge core from a 92-93. But, now that I think about it, here's where I get confused. If the gauge core has two windings then it also needs four connections, unless a three-pin gauge can use a common ground. My cluster backplane only has room for three pins. Sounds like I might need the entire cluster in order to utilize the four-pin gauge.
Also, as I reread My4Fordtrucks' comment, he has an 89 which, I think, already had the proper gauge installed. This fits with my belief that gauges up to the late 80's early 90's already have the proper gauge installed even if the on/off pressure switch was used. That's why I grabbed the one I have from the 90's model I found.
Anyway, McLeod, if you could share pictures of the rear of the consoles that might help to know if they are 3 or 4 pin gauges. This might help answer if I need a whole cluster backplane, or to seek a different (eg, 3 pin, dual-winding) gauge core, at which point I just might shelve this idea. A year ago there were a dozen of these trucks in nearby yards. This year it's about half.
1995 tach cluster oil gauge pod:
Note: resistors across leads in addition to resistor on circuit board, metal shell is slightly different than my 1993 and 1995 and the white plastic "wings" are part of the inner winding assmbly
1996 tach cluster oil gauge pod:
Looks similar to my 1993 externally
On all of these they are as follows:
top terminal is ground,
left terminal is signal
right terminal is ignition
Is there a way to see if they do what you need while they are sitting on the workbench?
Looking for a full swing vs a 1/2 swing with voltage applied?
What voltage do the gauges operate on?
Thank you for those. Mine didn't have that resister across the pins. Might be a clue in some way.
Unfortunately, I don't know how to check them. I'd assume 12v, but if it comes from the PCU then it might be only 5V. Assumptions have caused a lot of problems so I only use them when "testing" things I don't intent to keep around or if mild explosives are involved.
To my understanding, the reason the gauge only works to halfway is because coil-based gauges need to have 3 coils in order to read right, and ford dropped the extra coil because they had no intentions of returning to an actual-gauge which is a shame.
But I could be wrong. Simply because the gauge is unlabled and unumbered, I would want to use an external or aftermarket gauge anyway. Althoguh Im more inclined to use a sender to an electric gauge, because id be less comfortable with an oil feed line running to a gauge, but they are both options.
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