1978 Cherokee - Master Fuse?

Stock FSJ Tech Area
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Topic author
ChiefWoohaw
Posts: 2
Joined: Sat Jun 30, 2018 8:51 pm

1978 Cherokee - Master Fuse?

Post by ChiefWoohaw »

Pulling Jeep onto trailer upon buying it and it shorted by the solenoid. Replaced the solenoid and the shorted wire and nothing. No power at all. Have power going to the solenoid and if I jump it the starter spins but no power anywhere. I switched to two 30a fuses in the box but no luck. Any assistance on the next step would be great. Thank you!!
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tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: 1978 Cherokee - Master Fuse?

Post by tgreese »

There is a fusible link that you've likely blown. It's in the harness next to the solenoid. Here http://oljeep.com/gw/elec/78/78_FSJ_Wir ... mPage7.jpg 55B yellow 14 ga fusible link. Pull on it and it should stretch like a crispy rubber band if blown, or test it with your multimeter. You can get a replacement at the parts store or from Amazon. https://www.amazon.com/Bussmann-BP-FL-1 ... dpSrc=srch

You need the TSM https://www.rockauto.com/en/moreinfo.ph ... 90&jsn=368
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

Topic author
ChiefWoohaw
Posts: 2
Joined: Sat Jun 30, 2018 8:51 pm

Re: 1978 Cherokee - Master Fuse?

Post by ChiefWoohaw »

That wire and link are getting power all the way to the box on the firewall.

From looking at the diagram I was really hoping that was it.
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tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: 1978 Cherokee - Master Fuse?

Post by tgreese »

All you can do is trace the power cable. The ammeter is another problematic component. Assuming this Jeep still has its ammeter, power has to go through the ammeter to splice B to feed the ignition. Here is the diagram http://oljeep.com/gw/elec/78/78_FSJ_Wir ... mPage8.jpg - you see 55 go through he firewall bulkhead connector and to the ammeter. From the ammeter, wire 12 (I suspect it's actually a 10 ga wire - a misprint) goes to splice B, then continues as 12A back to the alternator. Before the alternator starts charging, all power to the Jeep has to go through the ammeter. I would check there next. You can reach it if you remove the cardboard glove box. Not sure you can reach it from below with the cluster and glove box in place.

You could slide the cluster out, but be very careful - there's a lot of stuff attached to it, and you don't want to break any of the connectors or pins in the cluster. You'll need to remove the steering column trim, unbolt from the bottom of the dash and lower the steering column an inch or two. You will definitely have to disconnect the speedometer cable. Do not power up the jeep without grounding the cluster - normally ground goes through the attaching screws. You will damage the gauges if the cluster is not grounded and you turn the key on.

An easy way to bypass the ammeter is to put both cables on the same post.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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