To fix or replace wiring harness

[mallard]

Tested everything tonight. here are the four test I did tonight with three gauges and two senders

test 1: Connect volt meter to where 36 wire plugs into oil pressure gauge.
test baseline info:
Battery voltage is 25.5 volts with switch on engine off. (same voltage when I checked the 27 wire going into the back of the gauge).
Desired reading from volt meter: 3-4 volts
results:
Gauge 1: 2.07v FAIL but see note below
Gauge 2: 2.06v FAIL but see note below
Gauge 3:0.1v FAIL

Note: Test two is basically the same test as test 1, it is just taking the reading at the wire 36 wire in the engine compartment that plugs into the oil pressure sender but gives a different desired voltage.

Test 2: switch on engine off, check voltage on 36 wire in engine bay
Desired reading from 36 wire: 0-2volts

Gauge 1: 2.07v Fail but only off .07v
Gauge 2: 2.09v Fail but only off .09v
Gauge 3: no reading FAIL

By now I have ruled gauge 3 out as bad, gauge 1 and 2 both failed but are very close. Can someone explain the reasoning behind the desired voltage changing from 3-4v to 0-2 when logically I would think they would be the same, reading one is from the back of the gauge, reading 2 is from the wire plugged into the back of the gauge???


On to the oil pressure sender test
Test 1: disconnect 36 wire from sender and check resistance to the oil pressure sender with switch on, engine off.
Desired reading: less than 1 ohm
Sender 1: 0.2ohms PASS
Sender 2: 0.3ohms PASS

Test 2: same test but switch on, Engine On, High Idle
Desired reading: 6-10 ohms
Sender 1: 18ohms FAIL See note below
Sender 2: 25ohms FAIL See note below

While it failed both test in the manual it says to refer to conversion table in test 3 for a conversion of resistance values to pressure. in the table it shows 18ohms= 35 psi, and 25ohms would be between 40-60 psi. I have a mechanical gauge screwed into the old fuel pressure cut off switch location and it was reading 40PSI which is close to both sender readings. the desired reading of 6-10ohms = 10-20psi oil pressure.

if you made it this far I would love to hear your thoughts???? Thanks again to everyone for helping me through this.

[rickf]

You never check resistance with power applied. That is a good way to pop the fuse in your meter or smoke the meter. the resistance reading is from the terminal on the sender to the outside body of the sender or a good ground on the engine. You are only measuring resistance of the sender. You did not go from wire to sender so no harm to the gauge. Ignition on with wire off does nothing to the setting.

Can someone explain the reasoning behind the desired voltage changing from 3-4v to 0-2 when logically I would think they would be the same, reading one is from the back of the gauge, reading 2 is from the wire plugged into the back of the gauge???

I do not understand what you are asking? The voltages are within .02 volt max difference from gauge settings. As far as why they are not at spec this would indicate a high resistance in the gauge circuit I believe.

[mallard]

The readings I am seeing are almost identical which is what I expected. But in the manual it says I should get 3-4volts coming out of the gauge in test one. In test two I am supposed to plug in the wire and check the voltage on the other end where it plugs into the sender and now it calls for 0-2 volts.

I would think it should be looking for either 3-4 volts at both places or 0-2 volts at both places.

Also to add I also ran a jumper wire from the sending unit to the gauge to eliminate the 36 wire just to rule out a bad wire after I test everything else.

One more thing can someone verify for me to make sure I have the wire hooked up correctly in the gauge. The 27 wire has a smooth boot and should plug in on the outer edge of the gauge panel in the smooth boot of the gauge.
The 36 wire with ribbed boot should plug into the corresponding ribbed boot of the gauge.

[mallard]

Friend grabbed one out his parts jeep and now it is working, so one problem down and now a new one popped up.

While messing with the gauge I unhooked my Speedo cable, when I tried to hook it up I couldn’t get it to thread on so I took it off at the transmission, then hooked it up at the gauge then hooked back to the transmission. Now the odometer portion seems to work but the speedometer acts up.

Just raving the gas with the clutch in it will fluctuate, when I pull forward the gauge wraps all the way around, if I back up it will go back to 0.

[rickf]

Pull the cable back off of the speedo and spin the center piece by hand. One way should go up and the other way should do nothing. If it climbs and stays there the speedo is bad. If it does work good then the cable may have been jamming something in there. You can buy universal replacement inner cables but if the cable housing is kinked or internally damaged it would do the same thing with a new inner. Take the whole cable out and spin the cable by hand while bending the housing the same way it is in the vehicle. There should be no roughness or binding. Pull the inner out and see if it is frayed anywhere.

[mallard]

Thanks Rick, I guess my speedo bit the dust, when spinning the back of the Speedo the same rotation as the gauge speeding up, in one revolution or less the gauge pegs out. Spinning the other way takes a few more revolutions but will get to 0 without much effort

[rickf]

Sounds like it is bad.

[Hambone]

I probably have a speedo if needed.

[Hambone]

Parts headed you way.

[mallard]

Parts headed you way.

Speedo and battery brackets showed up today and look great, hopefully can get the speedo installed in the next two weeks but won't be able to give it a test drive before then due to a foot surgery, not sure I'm good enough to pull of driving this with one foot but using the hand throttle has crossed my mind

[rickf]

Start out in first gear, no gas needed. Shift to second with clutch and then use left foot for gas and shift without the clutch. I have had many operations on my right leg and have just a bit of experience. LOL. This is NOT recommended for street use. (Yes, I did)