Pitot-tube Speedometer Diagnostic Methods
Pitot-tube Speedometer Diagnostic Methods
[I am diagnosing] the malfunction of speedometer system. If I hook a pitot tube to the speedometer and draw a vacuum by sucking the tube, should I be able to move the needle on the speedometer? Thanks
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- Joined: Mon Jul 31, 2017 9:33 am
Re: Speedometer not working
No, you need pressure to check the gage, and the amount isn't that small. That is, you probably can't blow on the tube enough to make it register. Here's a typical calibration for Teleflex speedometer:
If you have a pressure gage or hook it up to a pressure source you can check your calibration.
Boat speedometers are just good old fashioned Bourdon-tube pressure gages, calibrated to read in speed rather than PSI.
5 PSI = 20 MPH
11 PSI = 30 MPH
19 PSI = 40 MPH
30 PSI = 50 MPH
If you have a pressure gage or hook it up to a pressure source you can check your calibration.
Boat speedometers are just good old fashioned Bourdon-tube pressure gages, calibrated to read in speed rather than PSI.