Oil Pressure Sender

[WVZR-1]

Originally Posted by csavaglio

Jim,
That sounds EXACTLY what my readings are with the Duralast and my original was bouncing around, but not as extreme.

I'll post if I come up with anything. The more stuff I look up between part numbers, the more confused I get. For the record, I have a Duralast PS220 in there now (the one that comes up on Autozone's site).

Chris

I don't know where you got the interchange that you mention for the PS245 but it's wrong. That's an old "bell" sensor and not correct. I believe my work is correct! Duralast is A-zone and I still get the same PS220 BUT it's not the interchange and reference material I used. Like I mentioned - if you bought Duralast exchange it! Both of you JFFerner also. Why wouldn't you do that first? OR explain that an acquaintance has a similar results with his of the same part number and have them do a different brand or maybe offer a return and a refund.

The 12555492 if you found a dealer with that part number on the shelf would likely still be an ACD product but the newer service replacement is likely just a "repackaged" product from another vendor. There should be dealers with the older number on the shelf.

[csavaglio]

The interchange was on Summit....if you search that GM PN, it comes up with that. It didn't look right at all and that's why I said it.

As I said, my first plan is to find a parts store with another PS220 in stock I can exchange mine for. But, I'm in a small town and that's easier said than done. They do have a Valucraft (PS220-VC) in stock and the local Autozone is really good about exchanging for other brands.

After that, I'll start investigating about what pressure the car's actually making with a pressure gauge tool and go from there.

Chris

[csavaglio]

Ok, an update. I played around with it a bit after work.

I had the local Autozone swap it out with the Valucraft one.....they didn't have another Duralast in stock. I got exactly the same readings and the body had the same markings. I would not be surprised if they were supplied by the same manufacturer.

Cold, the gauge pegged full high. Warm idle, it was sitting about 2/3 or 3/4 up the gauge what I'd guess is about 60. anything above idle and it went up to a solid 80psi.

I picked up an oil pressure test tool.....looks a lot like a compression gauge.

Warm idle, I had a solid 22psi and at a steady 2500 rpm, it went up to about 60. It went a little higher, going higher up in the throttle.

So the car's actual oil pressure is spot on for what it should be.

Either the new senders are calibrated wrong......giving too high a resistance (sender unplugged with an open circuit, it pegs the gauge the right, well off the markings on the gauge), or the gauge itself is the problem.

There's a little cap inside the new sending units with a small brass screw in there. The good news is that it's an adjustment screw. The bad news is that turned all the way in, it makes the gauge read about 70 at idle and turned all the way out it still reads way too high at around 50.

As reference, my old sending unit read correctly (minus the fluctuations).

I guess this leaves me with a few options.
-I can go down to Napa and Carquest and hopefully they have the correct one in their brand.
-I can order a Delco one and see what it does
-I can try to verify the gauge substituting known value resistors in place of the sender
-Or just live with a wildly inaccurate gauge.

Chris

[csavaglio]

Can someone with a multimeter do me a favor and ohm out the oil sender wire to ground?

I'm testing how much resistance there is through the gauge. If mine is higher than it should be, it's going to make the gauge read high.

If possible, someone with a accurate gauge.

Thanks
C

[Racinfan83]

I got this one from Jerry's Gaskets - works great!
http://jerrysgaskets.com/store2/root...roducts_id=106

[csavaglio]

Better yet, can someone ohm their sender out while the car is idling and warm, i.e. when their gauge shows about 20psi, or 1/4 of the way from 0 on the gauge.

At this point, I'm not convinced it's the sending unit that's the issue. It seems like there's extra resistance in the circuit somewhere, but I can't find in the FSM anything on the circuit other than a really simple wire diagram with the gauge on one end of the wire and the sender on the other.



Thanks
Chris

[WVZR-1]

Originally Posted by csavaglio

Better yet, can someone ohm their sender out while the car is idling and warm, i.e. when their gauge shows about 20psi, or 1/4 of the way from 0 on the gauge.

At this point, I'm not convinced it's the sending unit that's the issue. It seems like there's extra resistance in the circuit somewhere, but I can't find in the FSM anything on the circuit other than a really simple wire diagram with the gauge on one end of the wire and the sender on the other.
Thanks
Chris

It's been a very long time since I've had to do cluster diagnostics on anything but I couldn't remember struggling quite like I had yesterday. Well it seems you've a FSM so if you go to 8A-82-11 Chart #3 you'll see the approximate resistance values that the dash gauge wants to see. Using your DMM you could check the sending unit for it's output similarly. It's very straight forward and I feel a bit foolish not catching it yesterday. I think the last cluster I maybe needed to check OP gauge on was maybe an '85 CK truck that I felt displayed low. That truck was new then. It used the "bell type" sender you stumbled on yesterday at Summit.

The real KM "signal generator" still brings a pretty hefty price on eBay. There was one that looked pretty realistically priced.

Haven't seen "scottfab" for a while maybe he could explain how to use a 100 Ohm potentiometer as a signal generator to check the cluster.

[csavaglio]

Ok, problem solved.

Here's what I found out:

The factory gauge is, as was theorized by another poster, 0-100 ohms.
The FSM, to test, says to apply 0 ohms and it should peg the gauge to 0 psi, 100 ohms pegs it to full high. It says 40 ohms should read around 30psi on the gauge.

I even ohmed out the connector to make sure it wasn't giving a bad connection and adding extra resistance (which would make the gauge read high).

The Wells made senders I received (Valucraft and Duralast) both were producing around 15-20 ohms too much, making the gauge read about 20-30 psi too high. At a cold idle, the car was actually making 65 psi and the Valucraft sender was showing nearly 110 ohms, pegging the gauge out at full high. So, the specs that were posted by another forum member above that Wells published were not accurate to the sending units I received. If they were, my gauge would've functioned correctly.

I went down to Napa and the guy gave Echlin a call to find out what the ohm scale was for their sending unit. Basically, it was very similar to the numbers that Wells officially published. It's a 0-80 psi sender, with 80 coming in at something like 65-93 ohms.

In the parking lot, I put in the new Echlin sender, part number OP6677. I haven't ohmed it yet, but it works perfectly. At warm idle, the gauge reads about 1/4 from 0, which should correspond to the 20psi the car is actually making.

For the record, I also have a NOS Delco one coming, same part number as the one at Jerry's. If I feel up to it, I'll test it out and see what readings I get off of it.


Being that Wells produced both sending units that had identical calibration issues, I think that either they're calibrating them incorrect for our application or there was a bad batch of units. As I said, I have a Duralast/Wells sender in my LT4, and it works well, but does read a little low compared to the working factory one (that I busted putting the intake on....).

The Echlin one looked slightly different inside the connector and at the base of the body, so I don't think it was produced by Wells.

Hopefully all of this helps someone out there.

Thanks, everyone for the suggestions and help.

Chris

[csavaglio]

WVZR-1,

Thank you for the chart.....For some reason, when I was troubleshooting after work yesterday evening, I could not, for the life of me, find that chart. I was thumbing through the manual in bed before going to sleep (don't judge me.....) and managed to find a reference to the chart by going to the engine section. I think it gave me the right wording to look for in the index. That chart is pretty simple, but then again, so is that circuit. It gives enough info to figure it out. 14 years of working in the satellite communications industry with an electronics background does help, though.

That's where I got the info for the what the factory gauge is looking for in the post above.

If all the gauges are 0-100 ohm, using a 100ohm potentiometer and a multimeter would make troubleshooting the gauges pretty easy. 100 ohms should peg the gauge out, 50ohms should make the gauge read about 1/2, etc. Assuming, of course, the gauges are linear. I don't think they are, but it would at least be a good troubleshooting tool to know whether you're dealing with a bad sender or gauge.

Chris

[JFFerner]

I got a new sensor from Jerry's Gaskets Part # 12555492-N,for $39.95
and installed it yesterday. Works perfectly. Now I only have to take the junk Duralast PS220 back to AZ.