TCCoA Forums banner

How to convert your oil pressure gauge (with pics)

126K views 208 replies 68 participants last post by  Grog6 
#1 · (Edited by Moderator)
Been wanting to try this so-called oil pressure gauge mod.
Based on Lonnie's tech article.

Tools needed:
Adjustable wrench
Large Pliers
teflon tape
10mm and 7mm sockets
Phillips screwdriver

There are 2 senders you can choose from:
Standard Motor Products: PS-60 Echlin: OP6091
Motorcraft: SW-1547-B, E4ZZ-9278-A *I used this one

I took off the old oil pressure sender with a pair of pliers.


Wrap teflon tape, about three turns, around the thread of the new sender. The Motorcraft one came with teflon tape already on the threads. I used an adjustable wrench to snug it down.

Reattach the sender lead. Shown in red.

Now you need to locate and bypass the 20ohm resistor.

According to the original tech article, Lonnie says "A small number of Thunderbirds have the 20 ohm resistor located on the oil sender wire approximately 5 inches from the sender itself. If this is the case, bypass or remove this resistor". You're done. Skip to the end.

Incase you don't have this resistor near your sender, it will be located behind your oil gauge in the cluster.

Here's how to take the cluster off without breaking the plastic tabs:
Applies to a 94 dash. Yours may vary

Remove these three bolts - 10mm


The bottom trim panel will pull right off. There are three spring clips holding the top on


This reveals 3 more 10mm bolts: (two I had already removed)


2 phillips screws


The surround can then be pulled straight back. It's also being held on by spring clips. Bring it back enough to unhook the rear defroster plug.


Tilt the steering wheel all the way down. Carefully work the surround out. It gives a little but too much and you could crack it.

The cluster is held on by four 7mm bolts in the four corners. If you needed to take the clear plastic cover off, you would use a T15 torx bit. You don't need to take the clear cover off for this though.


The cluster has 2 wiring harness connectors. You need to move the right-hand side out first to get at the one on the right side. This will give you access to get at the one on the left side. You press the tabs on the sides in and pull.


Reverse the above to put it back together again. Just remember you are dealing with plastic here. No need to crank down on the bolts.


This is the 20ohm resistor you're looking for. You need to work quickly so you don't melt the blue plastic. Take a piece of insulated wire and wrap the legs of the resistor.

Not the greatest of soldering jobs but my butane iron was a little too hot for this job.

Start it up and check for leaks.

From the original article:
When cold: between M and top line.
When hot at speed: M
When hot in gear idle: between N and O
When hot in park: O

This article demonstrates what I have done to modify my oil pressure gauge in my car. Neither I nor TCCoA assume any responsibility if you use this article to try to modify your own car. You do so at your own risk.
 
See less See more
10
#189 ·
Thanks for the update. One year bump. :bangwall:
 
#190 ·
LOL damn I'm lazy I still haven't done this, bought the parts 2+ years ago.
 
#193 ·
PS line bracket *$@$*

[sorry about the late bump, but it seemed like good information to add for any late/new thunderbird owners]

well i just did this on my 94 thunderbird LX - V8 4.6

I think if i would have read through all the threads, i would have probably considered the elbow. I couldn't really get the oil sender socket in because of a protector/bracket over the power steering line. I used the box end of the 1 1/16 wrench (mentioned in like the first part of the post) to get it lose.

Then I couldn't get the new bigger sender in, because of the bracket. i had to use a 8mm socket to get the bolt off, and a straight screw driver to pry it lose.

I was then able to get the sender in finger tight. And i did get a little oil around. Not a lot. But i did have the driver side front on a jackstand so i could fit under the car.

I tried to get that bracket back on, but it has this little grove on the end, just when I thought i was going to get it back in, i got it caught on the sender screw. And after a little bit, i decided to just leave it off. I didn't want to mess up the sender, or risk cracking the oil filter assembly.
 
#194 ·
[sorry about the late bump, but it seemed like good information to add for any late/new thunderbird owners]

well i just did this on my 94 thunderbird LX - V8 4.6

I think if i would have read through all the threads, i would have probably considered the elbow. I couldn't really get the oil sender socket in because of a protector/bracket over the power steering line. I used the box end of the 1 1/16 wrench (mentioned in like the first part of the post) to get it lose.

Then I couldn't get the new bigger sender in, because of the bracket. i had to use a 8mm socket to get the bolt off, and a straight screw driver to pry it lose.

I was then able to get the sender in finger tight. And i did get a little oil around. Not a lot. But i did have the driver side front on a jackstand so i could fit under the car.

I tried to get that bracket back on, but it has this little grove on the end, just when I thought i was going to get it back in, i got it caught on the sender screw. And after a little bit, i decided to just leave it off. I didn't want to mess up the sender, or risk cracking the oil filter assembly.
Is the '94-'95 V-8 set up differently than the' 97 V-8 is? I just did the conversion to my '97 T-Bird to install the' 94-'96 style instrument cluster in it, and I modified my oil pressure gauge per the instructions in this thread. I really had no difficulty such as you've described replacing my oil pressure switch with the bigger oil pressure sending unit. I wouldn't say it was super easy getting a wrench on the oil pressure sending unit to tighten it, but I had no such bracket you spoke of in the way, nor anything else I had to remove. So, I'm just wondering if the '94-'95 T-Birds/Cougars (and, maybe the 1996's, too) are different in some way from my' 97.

Or, if my '97 is MISSING something it's supposed to have, LOL!

Dennis
 
#195 · (Edited)
I hate to bump an old thread, but I'll be doing this conversion soon as part of a cluster swap (3 gauge base to 6 gauge sport) and I have a question. I'm pretty clear on everything but the fitting size needed to allow the new sender to clear other accessories. I have the Echlin unit from NAPA which has a 1/2" threaded connector, but the posts that mention the plumbing fittings all say to get 1/4". Is this a mistake or are there differences in sizes among the various brands of senders?

I've seen pics like this one, where the sender's threaded fitting matches mine as well as the old switch, so I'm a bit confused. Is the threaded part of the old switch 1/4" or 1/2"? My car is a 3.8 N/A.

ETA another question. How does the VMM get it's input? Will removing the stock switch affect it?
 

Attachments

#199 ·
... I'm pretty clear on everything but the fitting size needed to allow the new sender to clear other accessories. I have the Echlin unit from NAPA which has a 1/2" threaded connector, but the posts that mention the plumbing fittings all say to get 1/4". Is this a mistake or are there differences in sizes among the various brands of senders?
...
If the connections are the same size, you probably only need a 90 degree elbow in that size; that's what I needed for my 4.6l.

The analog sender is huge, and there's not much room there; it also needs to have room to move slightly with the engine, or it will hit something and loosen up, leaking oil.

If they're different sizes, take both to Home Depot or Lowes, and find a brass fitting that will adapt the two sizes together.

They've never had problems with me walking in with a handful of hardware to fit up. :)
If it's new hardware of the non-car variety, walk up to the customer service counter, and explain what you're doing; it will save shoplifting accusations later.

IIRC, the fittings are 1/4" NPT, which measures about 3/8"OD; pipe stuff goes by ID, not OD.

Make sure there are no trapped air bubbles, as it will make the readings iffy.
 
#196 ·
Would it be possible to re-link or provide new pics for this swap? I read all the way through the thread and most of the pics from 10+ years ago are gone.
 
#198 ·
I can’t specifically answer your question about the fittings, but the 89-93 VMM just uses a separate level sensor on the oil pan for its info, not the pressure switch input for the dummy light/gauge.


Frustratingly I intended to update the dead pics or make a new tech thread with my own during my engine swap but that obviously didn’t happen. Only pic I snapped during the conversion was the resistor jumper on the back of the cluster
 

Attachments

#200 ·
I can’t specifically answer your question about the fittings, but the 89-93 VMM just uses a separate level sensor on the oil pan for its info, not the pressure switch input for the dummy light/gauge.
Thanks! Good to know I won't lose the VMM when I do this.


If the connections are the same size, you probably only need a 90 degree elbow in that size; that's what I needed for my 4.6l.

The analog sender is huge, and there's not much room there; it also needs to have room to move slightly with the engine, or it will hit something and loosen up, leaking oil.

If they're different sizes, take both to Home Depot or Lowes, and find a brass fitting that will adapt the two sizes together.
Thanks. I intend to take them in for a good fit, I do that all the time also. So you're saying the stock switch is 1/4"? So I'll need to go from 1/4 to 1/2 to fit my sender.

As for the pictures, I don't know why they aren't showing up but a save pictures extension for Chrome was able to get most of them. Here are the ones I managed to save.

Original post:




















and Aaron K.'s pic from post 118:
 
#203 ·
Are there sending units with different ranges? I ask because this mod uses a 60psi max sensor, yes? When my mechanic was going through my motor (new water pump, headers) I was thinking of replacing the oil pump at the same time and he said I didn't want to do that unless I was prepared to basically rebuild the whole motor due to what an ordeal it would be to get to the pump and swap it out (disassembled so much, might as well finish the job). He checked the oil pressure and said it was strong and it was 80psi. So wouldn't it be better to get a sending unit that could read above 60psi? Or maybe it doesn't matter since the gauge face doesn't have numbers, just L and H?
 
#205 ·
Oh, ok, I just remember somewhere in the thread someone talking about a 90psi sending unit that he thought was the reason that the gauge was reading too low at certain points and maybe setting off a warning light or whatever. When I do this I'll probably go with the Motorcraft unit that doesn't need an adapter but I was curious if having one that reads up to 90psi was possible or recommended.
 
#206 ·
Oh, ok, I just remember somewhere in the thread someone talking about a 90psi sending unit that he thought was the reason that the gauge was reading too low at certain points and maybe setting off a warning light or whatever. When I do this I'll probably go with the Motorcraft unit that doesn't need an adapter but I was curious if having one that reads up to 90psi was possible or recommended.
I don't know if it matters. I figure 30psi is 30psi, it shouldn't matter if a sensor reads to 60, 90 or 300. And the Motorcraft is physically the same size and proportion as any of the others, if they need an adapter it will also.

I'm still confused about the thread sizes though. I saw a post on a truck forum where the guy has the same NAPA sender I have, and yet he also says he used a 1/4" threaded adapter.
 
#207 · (Edited)
Measure it with a tape; the sizes aren't that close:

Note that a 1/4" male NPT is over 1/2" in outside diameter.

They're tapered, so the nominal size is halfway up the threads, iirc.

Pipe stuff is INSIDE diameter size. (these gages have tiny holes, but if you look at a fitting, you'll see what I mean.)

The temperature sender on the intake is 1/2" npt; it's over 3/4" diameter. :)


 
#208 ·
I think I get it now (I can be slow sometimes :xpshame: ). The passage through the fitting is 1/4", not the threads. Got it now.

I took a look at the oil switch from under the hood today, just to see how much space there is around it, and the damn wire isn't connected! Might explain why I've never seen the oil light come on, fortunately I've never had an oil related issue. I assume the wire is hanging loose under there somewhere.
 
#209 · (Edited)
Pipe threads fucked me up too; I never really had to think about it until I had to tap the intake for another sensor.

I was really having a problem buying the tap and drill bit online, until I stopped at an old hardware store in Maryville, where dude told me about the ID vs OD thing.

Then it makes perfect sense, lol.

$20 bux worth of **** later, I had a PI intake working.

There's at least three types of pipe threads on our cars, the fittings on the tranny do not have a taper, and are British straight threads (BST), for some ******* reason. :)

There's another spot that's Straight threads, but american, so wtf. I can't remember at the moment where.


EDIT:

I finally found the numbers I measured from the sender I bought, a Performance products one.

NO Pressure to 10 psi = Open No Continuity

20psi = 26.8 ohms

40psi = 23.5 ohms

60psi = 17.4 ohms

80psi = 14.6 ohms

This was a 80psi sender; this has been the standard for ~50 years, apparently.

The Mark cars and 97's use a different sender with the resistance drop the other way; low to high. I THINK.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top