Oil Pressure Sending Unit

[John4337]

28,000 on my Mk4 and it seems that the sending unit is going south, couple of incidents of pressure going to 0, them back up, some erratic readings, etc. I have the Speedhut Gauges and my car dates from 2010. Does anyone know the part number?

https://thefactoryfiveforum.com/attachment.php?attachmentid=171156&d=1660600536

Thanks

John

[i.e.427]

Here you go.

https://speedhut.com/accessories/sensors/pressure-sensors/resistive-pressure-sensor-100-psi-240-33-ohms-line/?_ga=2.134631986.2132658306.1660610414-612345481.1657127445

Although, if you are the original owner of the gauges, they do have a lifetime warranty............. Just say'n

[cobrajj]

I had fluctuating oil pressure readings this weekend. I tapped the gauge and it immediately stablized at 60 psi. This has happened once before, so I think it's a loose connection at the gauge.

[Jeff Kleiner]

I’ve had several Speedhut oil pressure senders fail on multiple cars. They’ll replace it (because they know ;)).

Jeff

[John4337]

Thanks everyone, I had looked on the site, guess I didn't go deep enough. I've sent an email to Speedhut, I'll update when I hear back.

J

[John4337]

Well, got a response from Speedhut, they declined to cover the sender.

[egchewy79]

Well, got a response from Speedhut, they declined to cover the sender.

did they say why? was it too far out of warranty? I had one fail, but my build started in 2019, and they replaced it, no questions asked.

[John4337]

did they say why? was it too far out of warranty? I had one fail, but my build started in 2019, and they replaced it, no questions asked.

Here is the email reply. Sounds like an elapsed time issue.


John,

Im happy to help! Since it has been a while we are unable to warranty the sender you are more than welcome to buy a new one off our website if that helps you.
it sounds like the sensor here is a link for a direct replacement.

[Railroad]

I am unhappy to read their reply. I found great comfort in thinking I read, life time warranty.
I have one sensor replaced.

[mcwho]

28,000 on my Mk4 and it seems that the sending unit is going south, couple of incidents of pressure going to 0, them back up, some erratic readings, etc. I have the Speedhut Gauges and my car dates from 2010. Does anyone know the part number?

https://thefactoryfiveforum.com/attachment.php?attachmentid=171156&d=1660600536Thanks
John

Same issue started LAST WEEK. SAME vintage as John4337 2010 delivery date i think. Did some tests with my my Ohm Meter. engone off sener reads 243 OHMS with engine running, about 115 OHMS at about 60 psi, but its wobbling. I spoke to SPEEDHUT support last week, he said GuAGE IS LIFETIME warranty, sender is not.

also white connecter in dash reads 243 Ohms as well i disconnected from guage Fortunately I made my dash removable removable. I only have 2255 miles on the. MK gonna try and install today.

By the way, the original senter has screw terminals, and the replacement has spade lugs.

other info
Speedhut part # A-129 $30.45

[mcwho]

Another solution to the failing Oil Pressure sender part # A-129

Had a long talk with Rachael at Speedhut.
The 2 Wire Oil Pressure sensor as used in our FFR cars is used ONLY in the FFR setups.

There is another sender A-124 which has a 3 wire connector and requires a different Wiring harness A-107 to work. There is also a mod to the Current Guage or a new Guage with the 3 wire connectrion as required.

[Jim1855]

mcwho,

Did Rachael @ Speedhut indicate why the 3-wire was better, if it is? Will it solve the failing sender issue?

Any indication as to why FFR uses a 2-wire?

Jim

[i.e.427]

Who wants to tell Rachael @ Speedhut that it's not a matter of Factory Five gauge sets vs "all others" and really a matter of older Speedhut gauges vs newer?

[sread]

Don't feel too bad. I bought a set of gauges (including senders) from Classic Instruments for my hot rod build - about $650. The standard warranty is 7 years . I never buy extended warranties but for some reason paid an extra $20 to buy a lifetime warranty for these gauges. The very first road trip noticed the oil pressure gauge start bouncing around and would eventually settle on zero while running down the road at about 70. Long story short, but oil pressure is fine - repeatedly found that after about 15 - 20 minutes run time oil press gauge starts going wacky. I call Classic to inquire about warranty coverage and they tell me they will be happy to sell me a new sender or I can send in the gauge and they will check it out. Apparently the sender is not covered under warranty but the tech tells me if I buy one and it fixes the problem he may be able to get me some relief. Give me a f........ break!

[egchewy79]

Better question, why hasn't speedhut upgraded the sender/gauge to the 3 wire ones for the FFR kits?

I just checked speedhut's website and they state they have lifetime warranty on gauges but only a 5 yr warranty on gauge related hardware. I assume the senders are in that category. When I had mine replaced, they didn't ask me how old the sender was. They sent a new one the following week, no questions asked. Not sure how they can prove that your sender is >5 yrs old.

[narly1]

Windy discussion of the difference between 2 and 3 wire pressure gauges follows:

2-wire gauges are passive. They use a variable resistor with one side connected to ground (1st connection) and the other to the wiper (2nd connection). The wiper is connected mechanically to a diaphragm inside the pressure port. When the oil pressure deflects the diaphragm it moves the wiper on the resistor windings or track. So the resistance between the two connections varies with oil pressure, and this is what the dashboard gauge is measuring: varying resistance.


The issue with this scheme is that it is what I call "contacting" (wiper to winding/track) technology. So any failure between those two contacting elements over time (could be sticking, or poor/lost altogether contact) will cause problems.

By contrast a 3 wire gauge is more so what I would call a "non-contacting" device. It has a power supply running into it (1st connection) and through the magic of electronics outputs a variable voltage (2nd connection) wrt ground (3rd connection) wrt oil pressure. They way the electronics inside the sensor works centers around a resistive element bonded to the diaphragm. This bonding is very reliable. The element's resistance changes as it is flexed by the diaphragm. This varying resistance is fed into one leg of electronic circuit called a Wheatstone bridge which converts it into a varying voltage and this is what the dashboard gauge reads.

In the case of both types the sensor and gauge characteristics (variable resistance range, output voltage range) must match up for accurate readings.

I would submit that different companies probably use different resistance and voltage ranges in their designs so you generally can't mix and match sensors and gauges within the type (resistance or voltage) of technology. This also forces the consumer to buy parts from them exclusively.

Earl

[mcwho]

She mentioned that it was the insistance of factory five to use that sender. She implied that the 3 wire sender was a better unit but no specifics. I asked more about reliability next time we speak. My guage is in transit to speedhut for modification. I did some searching on RA regarding those types of senders and it seems to match up with a GM type of sender.

I only have a bit more than 2000 miles on my ffr.

By the way Jeff Kleiner mentiond this: "I’ve had several Speedhut oil pressure senders fail on multiple cars".

[mcwho]

I’ve had several Speedhut oil pressure senders fail on multiple cars. They’ll replace it (because they know ;)).

Jeff

Jeff, Thanks on your input on this issue.
Bob

[Jim1855]

Just an FYI.

Just looked and the pressure sender on my gauges is a 3-wire. I purchased direct from Speedhut a few years ago.

Jim

[John4337]

Well, the new sender arrived, sort of a pain to install and switch to the spade connectors, but now I have no oil pressure showing. I redid the spade connections just to be sure..... ugh

https://thefactoryfiveforum.com/attachment.php?attachmentid=171474&d=1661444978

[John4337]

Update - I have 240 ohms with engine off, no reading at idle, I'm very confused.

[narly1]

Update - I have 240 ohms with engine off, no reading at idle, I'm very confused.

What does the gauge require the resistance to be at zero pressure? Have you asked the gauge manufacturer?

Earl

[John4337]

What does the gauge require the resistance to be at zero pressure? Have you asked the gauge manufacturer?

Earl

I'm not sure, have a call in to Speedhut tech support. I rechecked all the connections and got a reading, seems a bit high, 75 psi at idle, but its progress.

[John4337]

I got a call from Speedhut, the new sender grounds only thru the threads, and he said a weak ground would cause a higher reading. I pulled the sender and removed most of the teflon tape and reinstalled. The reading went down a bit, but not much. I think i'll let it ride for a bit and see what happens.

[egchewy79]

my replacement speedhut pressure gauge gave me a higher reading than the prior one before it broke. old one was around 40-50psi, new one will start around 70 and then seem to drop into the 40s once oil is fully warmed. Not sure who to believe, but at least I have pressure.

[John4337]

[QUOTE but at least I have pressure.[/QUOTE]

My feeling as well.

[mcwho]

my replacement speedhut pressure gauge gave me a higher reading than the prior one before it broke. old one was around 40-50psi, new one will start around 70 and then seem to drop into the 40s once oil is fully warmed. Not sure who to believe, but at least I have pressure.

my measurement of the the 2 wire sender (old) was 243 Ohms w engine off. and 115 ohms with the engine running just above idle.

So i spoke to Speedhut again, I ordered the newer 3 wire sender, sent the guage for them to convert to the 3 wire setup. and ordered a wiring loom (8 foot) to attach the guage to the sender.

The Guage cable has 3 connectors. they are :

a black
black grey

b white
black
red

c yellow black
yellow red
yellow green

the sender cable has 1 connector, colors are
D white
red
black

the color code on the sender cable matches the white black red / white red black of the guage/sender cable, BUT the only 2 connectors connect with a click when connected is the c connector on the guage and the D sender cable.

In my experience the colors of the cable coming from the guage and the one sender would have the same color code. more info when i pull the dash again.

[mcwho]

Pics of sender cable and guage cable
the pic to the right shows the single cable tht goes to the sender on the left and the 3 cables that come from the guage to the right.

the pic on the left shows the only two cables that match up and click together

not logical in my opinion.

Update: just spoke with Amman at speedhut, the picture showing the yellow black / yellow red / yellow green cable from the guage connected to the cable that goes to the sender is correct. as in picture to the left.

[mcwho]

John_4337
can you tell me what size that hex nut is on the 2 wire sender ? im trying to remove mine, seems like it may be 9/16, unfortunately the spade lugs face me and I cannot easily see nor turm the sender.from that nut. i have to grab the CAN with vise grip. but I may have to remove my power steering pump.

you may be able to see the crowded area where the sender is.

[John4337]

Yeah it’s tight there. The piece your asking about is 3/4, but I couldn’t get a wrench in there, ended up using a small crescent wrench. You have work by touch.

[mcwho]

I'll try that i can only grab the sender by the large "can" part it seems like the can it turning and the nut on the sender is not turning.

[mcwho]

Finakky got it out 3/4 is correct i used an extremely small 4" crescent wrench.

Notice there is NOT any teflon tape on the threads or insice the conector.

Comments whether i should or should NOT use teflon tape on this fitting ?

[John4337]

Speedhut tech told me the new unit grounds only thru the threads, not the harness and to use Teflon tape only at the end of the threads.

[mcwho]

interesting, that may be true for the 2 wire sensor. the 3 wire sensor has the 3 wires,
this is from the speedhut wiring diagram 3 wire sender:

- signal white
- black ground
- red 5 volt referance

according to my VOM the ground wire does not also connect to the shell
-------------------------------------------------------------------------------------------------------------------------------
as long as I had just removed the 2 wire sensor i checked the terminals and found this.

there is no connection between either terminal and the shell.

[mcwho]

I am using a FLUKE ET3DMMA professional VOM

I believe that someone at speed hut may be confused as I show none of the 3 pins in the shell connect to the shell ground. Installed the new sender today and see wheat it reads at the speedhut oil pressure guage. why would a ground connect thru a wire connector in the shell and also ground thru the shell casing as well.

Just installed and tested the new sender and modified guage and 3 wire harness. at idle i am showing 55 psi and up to 65 up past 2000 rpm on 302 based 331 stroker. no leaks. no fluctations.

I did buy a set of extra thin open end wrenches, made twitsting the new sender a snap.

I'm happy with that.