The oil pressure gauge in my father's S5 vert is now non-functional (sits at the very bottom) due to the OEM pressure sender going bad. We took a known to be good pressure sender and put it on the vert and the factory gauge stays dead, but the gauge and sender work fine on another vert.

I'm looking to simply remove the faulty sender and use an aftermarket pressure gauge. Can anyone tell me if that will effect the ECU readings/behavior? From FSM diagrams it doesn't look like the OEM sender feeds into the ECU, it simply goes to the gauge.

Can anyone tell me if an adapter is needed/available for putting an aftermarket oil pressure sender in the factory location? I know sandwich adapters are available between the oil filter and oil pedestal, but my father doesn't want to get any further into aftermarket parts than he has to.

The other option is of course to replace the gauge cluster, but the car has bout 60k original miles on it. For insurance and resale reasons it's not a good idea swap. Also can anyone provide me a link to threads about replacing just the OEM pressure gauge?

I apologize about questions that could be answered with some searching, I'm trying to help him with his car stuff and haven't had time to both search his and my issues.

 

The OEM oil pressure sending unit is not electrically connected to the ECU.

Most aftermarket oil pressure sending units use NPT threads. The Rotary engine sending unit port is not threaded with NPT. You will an adapter fitting if the aftermarket sending unit is NPT.

MazdaTrix sells an easy install adapter plate that sandwiches between the oil filter pedestal and oil filter, which has two NPT threaded holes for both pressure and temperature sending units.

The oil pressure and voltage gauges are sold as a set by Mazda. The gauges cost about $110.

Hot_Dog
90 RX7 GXL

 

Aftermarket sending units will use NPT threads and the Mazda sending unit is BSPT.

What's the difference?
A 1/8 NPT fitting will have 27 threads per inch, the BSPT fitting will have 28.
NPT threads have a 60° thread with flat peaks and valleys, BSPT have 55° with rounded peaks and valleys.

The machinist in me says the fittings cannot be mixed/matched.
The shadetree mechanic responds that I've done it before and it works fine.

 

Thanks for the replies and not hammering me for not doing me searching first. I've been too busy with my own stuff to really look into his stuff also.

I'm pretty sure he'll go for the OEM gauges. He wasn't too keen on the idea of the sandwich adapter when I offered that option to him. He's in his mid 60's and not at all into the aftermarket rotary stuff. He's owned an RX since like 83, and has always been pretty content with how they came from the factory.

Ha!! I love the machinist to shadetree contrast. And thanks for the info on NPT to BSPT. I knew there was a different in thread patterns but other than them being threaded differently I never fully understood difference. Good stuff to know. Now I know when I'm trying to mix and match nuts and bolts why they'll look just about right but not thread right.

Hell someday when I'm bored and feeling **** retentive I'll better organize my mix and match jars.

 

have you tried grounding the sender wire to see if the gauge reacts?

 

My stock sender is actually leaking. I already have an aftermarket oil pressure gauge in the car, so I was going to remove the stock sender and plug the hole with a pipe plug.

I knew the block was BSPT, and had a 1/8 NPT plug, but I didn't like how the NPT plug felt going into the block, so I ordered a BSPT plug.

 

My stock sender is actually leaking. I already have an aftermarket oil pressure gauge in the car, so I was going to remove the stock sender and plug the hole with a pipe plug.

I knew the block was BSPT, and had a 1/8 NPT plug, but I didn't like how the NPT plug felt going into the block, so I ordered a BSPT plug.

 

HE has two verts, three between the two of us. He tried swapping a known working one from his black vert to the red one. Red gauge doesn't move with the good sender. The faulty sender from the red vert pegs out the black verts gauge. He turned the car off quickly to prevent the black gauge from frying also. This is all work my father did and told me about.


I found this thread on condensers

If that thread is accurate should I/we be looking to replace the condenser in both cars to prevent future gauges from frying?

Here's another related thread Cloker and Hailers endorsed Pretty much if Hailers says it, then it is true. Hailer's says Cloker is right then it must be true. HA! In other words Hailers = God...or Chuck Norris, take your pic!!!

With that last thread I linked in mind, I assume that a faulty sender can be grounding itself out, regardless of what the other wires, condensers and such are doing?

 

Can you tell me your source on getting them at that price. My father checked the local Stealership and they want something like $180-190!! At one time I had a spare S5 N/A gauge cluster. If I still have it I/we will simply take the gauge off that spare. If I've gotten rid of that I guess I'll put up a WTB

 

It's hard to tell with a tapered plug (or sending unit, for that matter) excatly how it is threading into the block.

Is it boogering up the thread or is that just the taper's interference fit that I'm feeling?

I have swapped between the stock and aftermarket sending units a few times now and had no leaks, so I'd tend to guess that the taper is wedging before the difference in thread pitch becomes a factor.

I've also wondered what would happen if one ran the NPT part through a BSPT die, but since I don't have one- and don't want to purchase it just on a whim- I can't say.

It's actually kind of frustrating.
NAPA- normally a pretty cheap source of parts- wants $100 for our oil pressure sending unit, simply because of the longer neck and BSPT threading. Our sender doesn't interchange with any other car, apparently it's completely unique to the RX-7.
In comparison, a "normal" sending unit is in the $30-40 range.

Thanks, Mazda.

 

At first I misunderstood what Dad was telling me. The faulty sender that fried the red verts gauge was pegging out the black verts gauge when put on that car. Is there a way to change that in the OP to do away with the confusion that's going to create?

 

Mazdatrix is selling the sending unit for $71.70

http://mazdatrix.com/getprice.asp?partnum=14-8200-N201

 

Yes, I know.

By way of comparison, egauges.com sells the sending unit for my VDO pressure gauge for $23.75.

 

Yea I think the taper is what you are feeling, Mine just did not feel right going in, and with the odd angle and tight confines, I did not want to mess with it. I have used NTP fittings in BSTP threads before and it worked out fine, but it did not give me a good feeling this time.

 

Point taken, they are more expensive than they need to be.

 

I don't remember exactly what I paid for the gauges, but it was somewhere around a hundred bucks.

Malloy Mazda
Woodbridge, VA
Ray Crowe, PM
703-490-8170

Hot_Dog
90 RX7 GXL

 

Thanks for the info