VDO oil pressure sender question

[Tom Duncan]

I replaced the 6 year old VDO pressures sensor (150psi, #360-430) that is recommended for use with the AIM MyChron3 Gold dash I have as I suspect it may be giving me false readings. At rest it reads -4lbs so that alone warrants investigation.

I replaced it with an identical VDO unit except it is 0-80lbs (#360-410). Now when I start the car the oil pressure reading goes to 125.5lbs and pegs (it was 56lbs the day before with the old sensor, same starting temps). Ellen at Veracity opined she saw no reason the 0-80 wouldn't work fine and I elected to go that way as I normally don't see pressures much above 55lbs (cold morning startup) and it seemed the sensing spread was more appropriate.

As near as I can tell it is not possible to calibrate the Oil pressure sensor as when I go into the calibration area the sensor does not show up. I pursued that path when the dash started to read out -4lbs a while back, a dead end.

Any ideas what I am doing wrong?

Tom Duncan
RF98K VD FF

[Tiago Santos]

So if I understand this correctly, you just replaced the sensor itself and kept the wiring the same, right?

Your data logger/dash is configured for the 150psi sensor, so the readings you are getting are as expected.. Both sensors are 10-180ohm sensors, meaning they read 10ohm at 0psi and (roughly..) 180ohm at full rated pressure. The 80psi sensor will read 180ohm at 80psi, while the 150psi will read 180ohm at 150psi. Might be the other way around (10ohm at full pressure, 180 at zero? It's been a while since I calibrated my logger..)

So your new sensor is reading the exact same pressure as the old one, but your data logger reads roughly twice the resistance, hence the pressure shows up as around double. The sensors aren't linear, so it won't be exactly double, but you get the idea

I do not have an AiM system, but I've played with the software before and I know there's a section to pick which sensor you're using with each input. Here's a video about calibrating a steering sensor, maybe you can figure out the appropriate steps from it:

http://vimeo.com/30217519

[Tom Duncan]

Thanks for the input Tiago, makes sense. Now that you mention it I do think buried in the program is a way to pick a sensor, I just have to find it.

Tom

[DaveB]

Look on their web site, some senders are grounded some are a floating ground.

Dave

[romoman]

To set the sensor, go into RS2 (the square one not the globe), then device configuration, then choose your logger. The sensors are listed under the channels tab.

[Frank C]

I have just gone through setting up a system. One goes to the Channels menu and for the channel with the sensor you select which sensor you have from a drop down menu - the ranges are listed.
- Frank C

[David Ferguson]

Your old one was a 10 bar (147 psi), and your new one is a 5 bar (73.5 psi)

[Tom Duncan]

Thanks all, it does indeed help to select the right sensor! I did manage to find it with your help. I remembered being there once before some years back once I got there. I switched to the VDO 5-bar and it now reads in the correct range. Interestingly when I fire up the engine it reads at 63lbs cold (64 degrees) which is about 3lbs/4lbs more than with the old sender (accounting for the -4lbs no pressure reading of the 0-150).

I will have to wait for tomorrow (when I can open the garage door and not wake up the neighbors) to do a full up-to-temp logging of the pressure readings to compare with the old sender, will let you know.

I really need to use the AIM software more than I do.

Tom