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OAT Probe

Where should the OAT probe be mounted?

• Install the OAT probe in the airframe manufacturer’s recommended location. If this information is not available, place out on the underside of the wing. Make sure probe is away from engine heat or exhaust. In this case it is recommended that the installation be done similar to the antenna installation instructions of AC 43.13-2A “Acceptable Methods, Techniques and Practices.” ** DO NOT USE COPPER WIRE.**

• Inside an inlet scoop or lower right corner of the front window on the airframe.

• Do not mount it behind the spinner because hot engine air exits as well as enters.

• Keep away from spiriling exhaust gases.

** The outside aluminum shield tube

EDM-700/800/760 Pin assignments

EDM-700/800 Pin assignments:
yel 1, red 2, OIL
yel 3, red 4, IND
yel 5, red 6, CARB (or CDT)
yel 14, red 15, OAT
yel 16, red 17, TIT
yel 18, red 19, TIT-2 (2nd TIT)
gry 12, Remote alarm (Sinks to ground)
red 13, + Power
wht 24 , RS-232 data port
blk 25, Engine ground. ** ( Pin # 11 not used.)

EDM-760 Pin assignments:
yel 1, red 2, Left TIT
yel 3, red 4, Left OIL or TIT2
yel 5, red 6, OAT
yel 9, red 10, Right TIT
yel 11, red 12, Right OIL or TIT2
gray 7, , Remote alarm ( sinks to ground)
red 8, , + Power
wht 13 , , RS-232 data port
blk 15, , Engine ground ****(pin#14 NOT USED )

OAT reads wrong

Run calibration procedure as defined in the Pilot’s Guide.

(1) To Run EDM calibration procedure:

Go to pilot program mode (Hold both buttons to see PROGRAM.
Tap STEP until you see OAT+0.
Tap or hold LF to change to OAT+ or OAT- a number up to 10.
Tap STEP repeatedly to END Y.
(2) Test in ice water bath (32F).

(3) Check all other temps – EGT, CHT – are they reading ambient temps OK?

(4) Confirm there are no splices with copper wire.

(5) Check ohm reading across probe 1.7 to 2.4 ohms

(6) Leads pinned backwards. Reading may be wrong but not negative or zero. It may decrease when actual temp increases & increase when actual temp decreases.

OAT temperature reading slowly climbs while on the ground

Check that EDM is grounded to the block.
Disconnect OAT probe from wire and twist together. Does it still do the same thing? If yes then connection issue see below.
Make sure there is no copper wire used with the thermocouple wire.
Put probe in ice water – does the temperature go up? – Then wired backwards.

OAT wrong

Be sure OAT is not in wrong temperature units (C or F) and Calibrate:

1. Go to pilot program mode (Hold both buttons to see PROGRAM.)
2. Tap STEP until you see OAT F or OAT C.
3. Tap LF to change to OAT C or OAT F.
4. Tap STEP repeatedly to END Y. Then tap ‘Step’ one more time to get out of PROGRAM mode.

To Calibrate..
1. Go to pilot program mode (Hold both buttons to see PROGRAM.)
2.Tap ‘Step’ until you see ‘OAT F’ (or C). Hold both the ‘Step’ and ‘LF’ till you see ‘OAT 0’.
3. Tap or hold LF to change to OAT+ or OAT- a number up to 10.
4. Tap ‘Step’ repeatedly to END Y. Then tap ‘Step’ one more time to get out of PROGRAM mode.

• Test the OAT probe in ice water bath. Should read 32°F or 0°C.

• Confirm there are no splices using copper wire.

• Probe may be mounted where it picks up engine or exhaust heat either from the spiraling slipstream or conduction through the skin. Try inside an inlet scoop or lower right corner of the front window on the airframe. Do not mount it behind the spinner because hot engine air exits as well as enters.