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J.P. Instruments » Slim Line

Slim Line

  • To check, short the white and grey wires at of of the shunt terminals and check if it reads zero amps.
  • Check that no other leads are connected to white and grey shunt leads.
  • Do not power unit from shunt lead.
  • (Advanced users only: Adjust amp reading on 10-turn pot on rear (right-most pot when facing rear of the unit)

• Check location of sensor. Make sure sensor is mounted as illustrated in installation manual. Look through vent hole to see rotating magnets. If you see a ‘gear’ you’re on the wrong one.

• Check with a tape recorder head degausser (available at Radio Shack): 4 cyl should read 3600 rpm and 6 cyl should read 2400 rpm; 8 cyl 1800; 9 cyl 1600; 4 cyl dual mag 1800; 6 cyl dual mag 2400.

• Check connections to sensor. Red wire should have 5v. Green wire 0 to 5v square wave.

• Make sure the correct sensor is being used:
Bendix series -20, -21, -200 Non-pressurized -#420815-2 — [Pressurize is # 420806.]
Bendix 1200 Non-pressurized -# 420815-2 — [Pressurize is # 420807.]
Bendix dual mag – D2000 or D3000 – No # -just specify “Bendix Dual”

 Slick 4000 or 6000 -Non-pressurized – #420815-1 — [Pressurize is # 420809.]
Slick 600 Pressurize is # 420806.

•With oscilloscope or Frequency Counter-( If they do not have these, ask if their digital voltmeter has the ‘Hz’ option on the dial. They can use that if it does. Meter’s red probe to the green wire on RPM sensor and the meter’s black probe to black ground wire on RPM harness. Do not use engine ground.) —- They should see these values per RPM / HZ:  500 RPM=12.50HZ; 1200 RPM=30.00HZ; 1550 RPM=38.75HZ; 1900 RPM=47.50HZ; 2250 RPM=56.25HZ; 2600 RPM=65.00HZ; 3500 RPM=87.50HZ

#1) Test the sensor – use Ohm meter:
0 PSI = 7.6 OHMS;
10 PSI = 24.1;
20 PSI = 39.4;
30 PSI = 52.6;
40 PSI = 63.6;
50 PSI = 75.0;
60 PSI = 87.6;
70 PSI = 98.6;
80 PSI = 109.5.
**(AT THESE PRESSURES YOU SHOULD SEE “AROUND”‘ THESE OHM VALUES-MAY NOT BE EXACT.)

#2)  To test the FP wire harness and the EDM, have them take both wires off the FP sensor and put in between those two wires(Black & White) a 39 ohm resistor. They should see around 20 PSI on the EDM. (If not they have a wire issue or an EDM issue.)

#1) To test the sensor – use Ohm meter:

0 PSI = 10.2 Ohms;  5 PSI = 34.2 Ohms;  10 PSI = 66.5 Ohms;  15 PSI = 95.3 Ohms;  20 PSI = 125.7 Ohms;  25 PSI = 151.7 Ohms;  30 PSI = 180.9 Ohms  (The should see ohm values close to the above. May  not be exact.)

 #2) To test the FP wire harness and the EDM, have them take both wires off the FP sensor and put in between those two wires(Black & White) a 66 ohm resistor. They should see around 10 PSI on the EDM. (If not they have a wire issue or an EDM issue.)

If ‘good’ the voltage should be:

Between Red & Blk        = 5v
Between Blk & White     = 2.5V
Between Blk & Green     = 2.5V
Between White & Green = 16.67mV.(‘milli’ volts) if pressure is around 10 psi.

 **[[ Between  the White & Green you should see around these other milli volt values per different PSI values. 8.33mV at 5psi;  25.0mV at 15 psi;  33.33mV at 20 psi;  41.67mV at 25 psi and 50.0mV at 30psi.]

Yes, we provide a 2.25″ round bezel adapter for the Slim so it will fit into a round 21/4″ hole. P/N 301055 — over 300 in stock.

Check instrument; it should read: 0 psi shorted. 146 psi open ckt.
Sender should read about 10 ohms ±5 with no pressure.
HOW TO CHECK IF THE TWO (2) WIRE 0-30 FP SENSOR: [Use Ohm meter]
0 PSI = 10.2 Ohms;
5 PSI = 34.2 Ohms;
10 PSI = 66.5 Ohms;
15 PSI = 95.3 Ohms;
20 PSI = 125.7 Ohms;
25 PSI = 151.7 Ohms
30 PSI = 180.9 Ohms
(AT THESE PRESSURES YOU SHOULD SEE “AROUND”‘ THESE OHM VALUES. MAY NOT BE EXACT)

HOW TO CHECK FOUR (4) WIRE 0-30 PSI SENSOR: [Use voltmeter]
If good the voltage should be:
Between RED & BLK = 5v;
Between BLK & WHITE= 2.5V;
Between BLK & GREEN=2.5V;
Between WHITE AND GREEN= 16.67mV. (milli volts) if pressure is around 10 psi.

** [ 8.33mV at 5psi; 25.0mV at 15 psi; 33.33mV at 20 psi; 41.67mV at 25 psi and 50.0mV at 30psi.]

Check instrument; it should read: 0 psi shorted. 644 psi open ckt. —
#1) To test two wire 0-30 PSI:  use Ohm meter: 0 PSI = 10.2 Ohms; 5 PSI = 34.2 Ohms; 10 PSI = 66.5 Ohms; 15 PSI = 95.3 Ohms; 20 PSI = 125.7 Ohms; 25 PSI = 151.7 Ohms; 30 PSI = 180.9 Ohms  (AT THESE PRESSURES YOU SHOULD SEE “AROUND”‘ THESE OHM VALUES. MAY NOT BE EXACT)

#2) To test two wire 0-150 PSI: use Ohm meter: 0 PSI = AROUND 7.6 OHMS; 10 PSI = 24.1; 20 PSI = 39.4; 30 PSI = 52.6; 40 PSI = 63.6; 50 PSI = 75.0; 60 PSI = 87.6; 70 PSI = 98.6; 80 PSI = 109.5. (AT THESE PRESSURES YOU SHOULD SEE “AROUND”‘ THESE OHM VALUES. MAY NOT BE EXACT.)


#3) To test the OIL P wire harness and the Slim, have them take both wires off the Oil Press sensor and put in between those two wires(Black & White) a 66 ohm resistor. They should see around 10 PSI on the Slim.( Depending on which sender they have 0-30 or 0-150. See above resistive values with their pressures values.)

Unplug the temperature probe harness off the Slim and turn power on. It should show the ambient air temp within five(5) degrees. If the temperature is way off,  then for a further check, have them put a wire across the two(2) pins that the temp probe harness connects to. (Short it out.) The Slim should read as above.  If not – then the Slim needs to come in for repair. Call Technical Support for RMA number before shipping.

There are two lights but they are wired together (except RPM Tach Slim).
All temperature Slim’s and MP Slim are red-line (too high).  
Oil Pressure Slim is too low.


Volt/Amp Slim displays reverse current (discharge). If used as a load meter, should never light. (Nothing to do with voltage.)


RPM Tach Slim: green is normal; yellow is precautionary; red is red-line.(At the time of ordering the RPM Tach Slim, the cust will send us his ‘green’ range, ‘yellow’ range, and ‘red’ range so these can be set into the Slim Tach RPM gage.)

Instrument 3 oz.
Fuel and Oil Pressure xducers 4.5 oz.

Slim-line:  2.0 x .950 x 3.5″ box (mounting ears 2 3/4 wide).