Instrument electrical issues - 84 cj7 - JeepForum.com
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post #1 of 13 Old 04-25-2021, 02:13 PM Thread Starter
JProctor
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Instrument electrical issues - 84 cj7

Not sure where to begin with this one but I have 2 main issues with the instruments:

1) Temp gauge “works”, but it doesn’t go much higher than cold. Oil Pressure gauge is very low once the vehicle gets to temp. May be an actual oil issue, but I would prefer to check for any potential electrical issues since the wiring is an absolute mess.

2) None of the instrument lights work. No idea why. Every gauge has at least some amount of functionality, but none of the lights work. Headlights, taillights, signals all work fine but I can’t see the speedometer at night, not that this thing is a speed demon, but it is slightly annoying.

Any tests or suggestions would be greatly appreciated. I am in possession of an owners manual from an older model cj7, but I can’t read wiring diagrams very proficiently so i didn’t get very far with that.

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post #2 of 13 Old 04-25-2021, 06:41 PM
texasdave
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Electrical Issue

Unless you are 2 ft tall an weigh 25 lbs and can wiggle through a key hole I recommend moving the dash. What I do is get a length of threaded rod and put a length of 6-8 inches and screw them into dash bolt holes on the top left and right corners. Now you can suspend the dash on the two rods and begin trouble shooting. On the back of the dash there are orange (4) and black (4) wires daisy chained. These power the dash lights for each component i.e. wiper switch, heater sw, headlight sw etc. You will need a multimeter. Check the voltage going into the light with headlight switch on. You get voltage then your lights are bad. You can order a set of replacements from the different vendors Quadratrac, Morris Ros etc. Your panel instrument lights will have a single orange wire going to the bulb. The light is grounded through speedometer casing. Let me know if this helps or works then we can start on the other stuff.
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post #3 of 13 Old 04-25-2021, 09:53 PM
JEEPFELLER
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See post 5 in here https://www.jeepforum.com/forum/f8/2...ormal-4424389/

My temp is normal w/ 195 degree stat---"Normal" is when it reaches the green line on the face.

Instrument lighting???

Cluster?

Rectangles beside the cable knobs?

Any of them working?

Here's a 1979 full diagram----much of it has not changed, especially the illumination

2nd diagram (right side of entire diagram)----nearer to the top, just below Reference #s "7" and "8" is the dash illumination.

It's so much EZer to have the office store blow up big and laminate your Correct diagram--tracing is then a cinch! It's there for the future!

-----JEEPFELLER
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1A LEFT SIDE 1979 CJ FINISHED 14DEC11.jpg   1A RIGHT SIDE 1979 CJ FINISHED 14DEC11.jpg  
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post #4 of 13 Old 04-26-2021, 12:04 AM
BagusJeep
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Temp gauge reading low could be a missing thermostat, poorly reading gauge or sensor or a bad connection or low voltage at the meter. The temp gauge when working needs a good connection to the sensor, it reads highest with no resistance.

I would check the coolant temperature at the thermostat housing before assuming the gauge is wrong.

BagusJeep lives in Bali with far too many 4x4s:
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
1980 Land Rover Series III 109" troop carrier - ROVER
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post #5 of 13 Old 04-26-2021, 04:56 AM
John Strenk
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Does the fuel gauge work? Accurately?


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I drive a Prius to save money and buy more Jeep Parts....
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post #6 of 13 Old 04-26-2021, 09:01 AM
torkman1983
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Before doing anything, run a dedicated ground from battery neg to a clean location on the back or bottom of the dash. May not fix your issues, but faulty grounds account for the majority of elec problems.
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post #7 of 13 Old 04-26-2021, 12:39 PM
JEEPFELLER
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Negative,

Not grounds destroying themselves.

The true "Jeep Juice" problem is

Personnel, messing with what they should not mess with, usually performing self taught trial and error,

Jeep electrical, but never "earning" that trial and error 'lectric certificate. Usually, inherited by the next same kind of guy.

Mostly this began (I'm guessing) 5-7 years after the new-ness wore off of the Jeep---the practice still is performed to this day, it's now exponentially out of hand.

----JEEPFELLER
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post #8 of 13 Old 04-26-2021, 12:45 PM
John Strenk
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That would fall under the Previous Owner Opportunity Probability. or P. O. O. P.

or something like that.


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post #9 of 13 Old 04-26-2021, 02:54 PM Thread Starter
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Quote:
Originally Posted by John Strenk View Post
Does the fuel gauge work? Accurately?
Yes it works fine, as well as the speedometer.
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post #10 of 13 Old 04-26-2021, 02:56 PM Thread Starter
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Quote:
Originally Posted by JEEPFELLER View Post
Negative,

Not grounds destroying themselves.

The true "Jeep Juice" problem is

Personnel, messing with what they should not mess with, usually performing self taught trial and error,

Jeep electrical, but never "earning" that trial and error 'lectric certificate. Usually, inherited by the next same kind of guy.

Mostly this began (I'm guessing) 5-7 years after the new-ness wore off of the Jeep---the practice still is performed to this day, it's now exponentially out of hand.

----JEEPFELLER
If you’d like any idea just how bad the electrical system is, the previous owner somehow managed to pull off an ECU delete. Exciting stuff.
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post #11 of 13 Old 05-15-2021, 06:57 PM Thread Starter
JProctor
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Quote:
Originally Posted by texasdave View Post
Unless you are 2 ft tall an weigh 25 lbs and can wiggle through a key hole I recommend moving the dash. What I do is get a length of threaded rod and put a length of 6-8 inches and screw them into dash bolt holes on the top left and right corners. Now you can suspend the dash on the two rods and begin trouble shooting. On the back of the dash there are orange (4) and black (4) wires daisy chained. These power the dash lights for each component i.e. wiper switch, heater sw, headlight sw etc. You will need a multimeter. Check the voltage going into the light with headlight switch on. You get voltage then your lights are bad. You can order a set of replacements from the different vendors Quadratrac, Morris Ros etc. Your panel instrument lights will have a single orange wire going to the bulb. The light is grounded through speedometer casing. Let me know if this helps or works then we can start on the other stuff.
Finally got some time and got around to this, checked the bulbs and they do work, no voltage through the wires though. The fuse is intact, and the headlights still work as always. I did discover an orange wire in the vicinity of the light switch box. I do not see any loose orange wires under the dash, just the one near the switch, has some kind of connector on it. Dome light also didn’t work if that information is relevant. Any further advice would be appreciated.
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post #12 of 13 Old 05-30-2021, 10:14 AM
Tundra-Honky
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Where did you get that amazing colored wiring schematic
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post #13 of 13 Old 05-30-2021, 10:32 AM
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Quote:
Originally Posted by Tundra-Honky View Post
Where did you get that amazing colored wiring schematic
Here's a place that sells them laminated. I ordered one year's ago, not sure if it was from here but its laminated also and is great.

You can Google "jeep cj wiring diagram" and pull up pics of same thing and print your own on a 11x17 and they come out fine usually.

https://colorwiringdiagrams.com/t/cj5--cj7

Sent from my SM-A015A using Tapatalk

80 CJ7-304/T176/D300 HEI hdrs-WT D30/D44 4.56s, lockright/spool-SOA YJs W/RE AAL-35 MTRs beadlocks
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