No power at relay purple & white

[trucker 1954]

Pluged a 12 volt fan into Fuse box power slot up from the bottom flasher. Truck was running ,fan ran and truck shut off .checked all fuses good / Did relay Mod nothing / Changed ignision switch nothing / All fuse links power up in engine bay. Truck is a bone stock 1028 1986 19,000 miles taking dash apart this week and re droping column to check power at ignision switch any Ideas, have lights horn 4 ways directionals /// no heater what would make my truck shut off when i plug into fuse box . have down loaded many diagrams and no two are alike but lots of good info great site great people

 

[doghead]

uunplug whatever you plugged in.

Check the lowest fuse in the fuse box.

 

[trucker 1954]

unpluged as soon as truck shut off would not restart all fuses good , looking if it has a saftey switch between the yellow from ignision switch and purple and white wire to start relay to night I have a miltimeter and a snap on test light All power leds in to cab power up with a test light Does the diode under dash have any thing to do with the start system The TM are my best shot but hard to find a test in writing , any help would be usefull Great Thanks Ron

 

[doghead]

Is your truck a 1983?

 

[trucker 1954]

1986 m1028a1 cotract Body

 

[doghead]

Test with the key in the run position, the pink power wire on the injector pump. Should have 12v.

To confirm your issue. Your truck was running, then it stalled/shut off when you connected the fan. And now it will not turn over/start when you turn the key to start.

 

[Warthog]

unpluged as soon as truck shut off would not restart all fuses good , looking if it has a saftey switch between the yellow from ignision switch and purple and white wire to start relay to night I have a miltimeter and a snap on test light All power leds in to cab power up with a test light Does the diode under dash have any thing to do with the start system The TM are my best shot but hard to find a test in writing , any help would be usefull Great Thanks Ron

The diode under the dash is for the GEN2 exciter circuit.

I don't think there is a test procedure in the TMs for your issue.

Can you point out where you pluged the fan into? Is it the circled slot?

There are a few circuits in the CUCV fusebox that are not shown in the wiring diagrams. Also you may have to use multiple diagrams to trace a circuit.

 

[Warthog]

If it you used the circled slot, you have popped the fusible link on the 12v terminal block next to the Glowplug Relay.

This fusible link feeds the ignition switch and the the heater circuit fuse.

 

[doghead]

I got a PM saying he went to work. we'll get back into it tonight.

That FL was where I was headed next(after he told me the orange wire is dead)!

 

[trucker 1954]

No start

Test with the key in the run position, the pink power wire on the injector pump. Should have 12v.

To confirm your issue. Your truck was running, then it stalled/shut off when you connected the fan. And now it will not turn over/start when you turn the key to start.

Yes it was running and pluged into the slot nest to the 10 amp fuse above the 30 amp on far right side of fuse box . truck shut down no power on the on or start no volt meter showing anything Im at work will check pink wire tonight with Key on

 

[trucker 1954]

No start pruple / white

You guys hit on the head 16 gauge link to 12 ga red in cab going to Napa the PN is 785832 link and conector is 784274 it showed power with test light put a load on link and what was left is now gone. Thanks for your Help Warthod and Doghead

 

[doghead]

Super! You should be able to get replacement fusible link(bulk) at your local NAPA or whatever.

 

[Warthog]

According to the diagrams, that is a 16 gauge link.

Good find. Glad we could help.

Us old farts get it right every once in awhile...

 

[doghead]

Who you calling old?

 

[Warthog]

Me.... I resemble that remark................