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454XL Oil Pressure Gauge Issue

390Express

Regular Contributor
Have a gauge acting up. (Crusader 454 XLs)


Grounded the sending unit wire on the stbd motor, gauge pegs, grounded the wire on the port motor, gauge goes to zero. Gauge also reads backward (reads 20 psi at idle, when it revs up, reads lower).


Could the wires be reversed on the gauge, causing reversed polarity, or time for a new gauge?
 
Sounds like the stbd is ok and the concern is with the port side??

The gagues typically don't work at all if powered with reverse polarity.

I'd check into it a bit deeper before condemning the gauge...could be the sending unit or a mismatch between the sending unit and the gauge. Are the gauges the same brand/style between port and starboard?
 
Sounds like the stbd is ok and the concern is with the port side??

The gagues typically don't work at all if powered with reverse polarity.

I'd check into it a bit deeper before condemning the gauge...could be the sending unit or a mismatch between the sending unit and the gauge. Are the gauges the same brand/style between port and starboard?


Gauge is factory VDO gauge, (both are VDO, but I believe the faces are slightly different) sending unit is a Sierra, West Marine replacement, for a 454 Crusader XL.

Starboard engine gauge is perfect.
 
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If the sending unit was recently changed, I'd be inclined to say wrong type was selected.

Swapping gauges is probably easiest test to be sure - you can just swap the SENDER wires with jumpers clips...I prefer to 5% tolerance resistors for testing the gauges.
 
Thanks Mako, under the dash there are two 9 pin connectors, I can swap the 9 pins and receive gauge information from the opposing side gauges. That should give me a pretty good idea what it going on.

I was under the impression that the 454's pretty much all used the same, 1/8 NPT, single screw post, 80psi 233 Ohm at "off" and 33 Ohm at 80 PSI sending unit... Gas gauge did me wrong as well... guy at the parts store "80% of them use this one here...." Yup, mine was the other...

I found a 10 Ohm - 180 Ohm gauge, which would explain perfectly why the gauge goes down and not up as pressure increases. VDO sucks!
 
The engine doesn't care about which sender is used...only the gauge. The 'US Standard' uses the 240-33 ohm senders for most gauges.

They also offer dual station (like upper and lower gauges at each helm) sending units...based on your description, that's not the issue.

All of the 'new' VDO gauges I've touched in the past 30+ years have been US standard types...some older ones I've seen used the euro senders...

That's why I use the resistors to assess the gauges...sometimes, you can get part numbers off the case but not always...
 
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