Headligjts dont work.. and bright light switch by foot has no plug ?

[letank]

A '76 comes with a Motorcraft alternator and regulator. Not the same as the Delco SI; "Systems Integrated" with the regulator inside the alternator. Seems blindingly obvious if you read the TSM.

Very good infos, I looked at this mod for the 74... but since the 74 has been mothballed... this is a very good resource!

Yes, the 74 has the motorola and the external voltage regulator

[tgreese]

As I recall, all models in '74 came with the venerable Motorola alternators and regulators. You can identify them by the exposed diode plate on the back. In 1975, Jeep started equipping the six cylinders engines with the 10SI, but the V8s kept the Motorola. My CJ-6 has the Motorola parts.

The Motorolas aren't terribly reliable - they tend to pop output diodes and then the output drops by some percentage. The regulators are solid state and ok, AFAIK. In the dealership shop of the day, they would take the alternators apart and solder in replacements for the individual failed diodes. Even with labor, less expensive to fix the alternator than to replace it. Bearing replacement was another common repair.

Don't know why Jeep did not commit to the clearly better 10SI for both the V8s and sixes... cost? contracts? availability? In 1976 they dropped the Motorolas altogether and went with the Ford Motorcraft alternator and its mechanical (!) regulator for the V8s. This continued through 1977. In 1978, they went to the 10SI for all models.

[candymancan]

Havr to check my 76s alternator again but i coulda swore it said motorola on the back. But i gatta clean it up and recheck ill report back when i do this swap to the 12si 94a.

Tbh it seems Jeep was all over the board in 76-78 with things

[candymancan]

well i added a ground to the tank, tank is deff grounded now when i checked with a 12v wire and my multimeter.. I checked the wire at the tank, the plug was corroded, had to cut back 13 inchs of wire to get to clean copper, tested the incoming wire with it disconnected at the tank end with a multimeter (meaning the wire going to the tank).. i am getting wild voltages on it, goes from .50v to 1v to 4v to 5v, and jumps up and down wildely all over from 5v down.

Gauge still doesnt work. so the ground works, power is going to that wire although its wildly jumping. And yea, i know the cluster oil and gas gaugee get 5v from the coolant gauge, but if the coolant gauge was bad then it and the oil wouldnt work, and those work. Is that jumping voltage normal ? Remember when my gas gauge didnt work, tapping it got it to perk back up.. then it slowely stopped working again.. ive tried tapping it, rubbing it, wiggling wire in the back of thee cluster. nothing

So i wonder if the fuel gauge itself just went bad. Any ideas. ?? Its annoying not having any idea what my fuel level is

[tgreese]

The "voltage regulator" in the temperature gauge turns on and off to "regulate" voltage for temp and fuel. That's where the pulsing comes from. Not abnormal. Shows that something, if not everything, is working.

Take the fuel gauge out of the cluster and test it on the bench. You'll need a 5 or 6 volt DC supply, which could be some batteries linked together, a voltage divider from a car battery, or a cheap benchtop power supply. Plus some resistors. You can do the same with the temperature gauge.

Read the '82 TSM on the TOm COllins site. Section 1L has an excellent flowchart for diagnosis, and exceptionally clear drawings. No change from '76.

[candymancan]

Why resisters ? Would a 6v 3amp car battery charger work ? Actually i think i might have a 5v charger for an old video game console that semds 5v. But why resisters ?

Ill look at the diagrams thanks

[candymancan]

Ok im following the diagnosis part on the tsm. The grounding the terminal section. Do i just ground it litterally. Or do i need resisters for that ? The grounding wire on the pic had a round object on it. So im not sure if i just hook up a wire to ground it to get the needle to move and thats it or what ?

[tgreese]

Resistors to mimic the sending unit.

Yes, ground it. The round thing is the probe on each end of a test lead.

[candymancan]

Well i did step 7 and 8
There is jumping voltage on the right terminal of the gauge or left if your looking at it. and the gauge jumped to full really quick when i grounded the other terminal... So im moving onto step 9 and going to jump the pin. Trying to do this with the cluster not removed. I hate removing these clusters.. last time the spedo cable took an hour of fighting to get back on..

Assuming its the pink one next to the terminal.

Edit : did step 9. jumped thr pink terminal pin with ground. Fuel guage shot to full.

So now its saying the next step is to repair the open circuit in the sending unit wire what does that mean ?. How do i go about doing that ? Im bad a electrical but im trying here.

Im assuming open circuit means broken wire.. but the wire all the way to the fuel tank plug has current.. so the wire isnt bad.

Does this mean my sending unit is bad ? Ima try ti drop the tank a little to get my hand up there and see if that plug came undone or somrthing up there

[candymancan]

Managed to unplug the pin at the sending unit with the tank in. It alsochas power.. so the gauge works when grounded. The gauge works when grounded at the pink pin. Tank is deff grounded if i test the pink wire and ground directly to the tank body.. The pink wire has power through to the pin at the sending unit itself on top

Then this means my sending unit is bad i guess.. ?? Damn this sux...

Also my tank is directly touching the floor i just rebuilt. Is that normal ok ? I noticed my fuel lines on the sending unit itself up there were directly against the new bedfloor i built. So was the sending unit plug. I might have to put some shims in where i bilt the tank ti the floor to keep it iff the floor a little bit. Again i had to rebuild the entire bed flpor. Cross members andcgas tabk mounts so maybe my mounts are too close to the floorboard

[tgreese]

Open circuit means not connected. Not a circuit.

Sending units are a common failure. Sorry. The replacements are often bad out of the box, and the originals seem not to age well, regardless of use. If you buy a new one, test it before you install.

The straps hold the tank against the bottom of the bed. Originally there was distance for the sender connection. Whatever you improvise should be ok as long as there is something solid for the tank to ride against, and the sender and lines have enough clearance. 2x4s?

You did good with following the TSM and diagnosing the problem. That's a success.

[candymancan]

So what brand replacement is good then so i have less of a chance of a bad one ?

[tgreese]

Likely the MTS ones are ok-ish. I expect that's what BJ's sells. Buy from BJ's and support the vendor that supports us. Quadratec would probably be ok too. All this stuff is import, and you don't know what you're getting, or if there is more than one source.

[candymancan]

I dont like bjs theyre overpriced. I cant spend my money like its water. Plus i dont like Ryan as a person had issues with him on fb and hes a real D. Gotten along just fine without bjs for all my Jeeps.

How do these things fail anyway they seem simple

[tgreese]

They are simple. They typically have a piece of resistance wire wound around a bakelite (?) circuit board. A wiper on the float arm slides along the coil and changes the resistance. Either the circuit board falls apart (constant exposure to gasoline?), the wire wears through (worn out), or the joint between the wiper and the arm pivot no longer conducts (corrosion or wear?). I've only seen a handful of them, but they were all bad after several decades.

I'm not certain it's MTS that's importing this part, but that's likely. If you search the MTS part number JPSU-1 https://www.bing.com/search?q=JPSU-1 you'll find a bunch of places selling the MTS part. Your choice.

[tgreese]

Also - sometimes the float sinks. You can buy a new float. Example - https://www.ebay.com/itm/273432941403

I've tried draining these brass floats and soldering shut, but they crack again where the arm stresses the brass where it fits in the groove. The price of replacements has gone up - I think I paid about $5 for a new float in 1985, Ford OEM part.

[candymancan]

I wish i took a pic of mine inside wbwn i cut the top of the tank out to repair it. But i dont remember mine being brass. But im probably wrong.

Do you think sticking a borescope in there to see if its floating or not would hurt . Or would i blow myself up haha

[tgreese]

I don't see how looking will help. If it reads empty constantly, the sender has to come out, regardless of the cause.

The new floats are plastic, but an original from '76 is probably brass.

[devildog80]

I was able to refurbish mine, as it was still intact but very dirty, so no reading.
I would encourage you to investigate the float more, and be sure it is functional or done for before ordering a new one, which might not work. My thoughts with mine were if I could get my original working, I would be leaps and bounds ahead in quality over the new ones being sold.
You can see my build thread, for details to clean mine up, which works perfectly now. I will say I got lucky, and mine was still intact, just dirty. Hope you find the same with yours.

[candymancan]

ill take a look ive seen others online using q tips and stuff cleaning the contacts and stuff, id rather try to fix mine that buy a chinese one. Well see ill let you all know.

And fyi i got my 12si alternator to work in my 76, i didnt even look for new mounting brackets like everyone says you need. I just modified mine a little easy actually to mount up. And i figured out how to re-wire the Jeep. Its fairly simple. Ima make a video on my youtube channel and post it here so people know what to do