Blown Dash Fuse

[Metacom]

Saw a few posts on this topic but they seem to be related to after market gages.

Completely stock ‘87 Grand National with a digital dash. After replacing the spark plugs, the 20A fuse for the dash is blowing right after starting the car. Any thoughts or where to start troubleshooting?

Thanks

 

[salvageV6]

Which 20A fuse is blowing, there's 2 for digital dash cars.

 

[Metacom]

The bottom one labeled gages next to the battery plug.

 

[salvageV6]

Here's what's on that fuse. I would start by unplugging the connector to the transmission with the 4 wires in it and see if the fuse holds. The gages fuse powers the torque converter lockup solenoid through the brake switch for the trans. You can also look for the pink/blk stripe wire on the connectors, there's (2) on the brake switch and unplug it there and see if the fuse holds. The wire can break inside the transmission case and short out to the metal in there. Otherwise you are looking at disconnecting the dash power to the instrument cluster plugs connectors with pink/blk wires in them and see if the fuse holds. Need to isloate the short somehow.

 

[salvageV6]

On the turbo cars the ECM/Sol fuse runs the TCC lockup so forget the transmission connector as a fix.
You probably have to unplug the dash connectors one at a time to see which pink/blk wire is the short into the dash, could be the turbo boost gauge lamps. the cluster itself, or the VSS sensor power.

 

[Chuck Leeper]

Working around the engine wiring when changing plugs...Look around there.

 

[Metacom]

Thanks for the info!

 

[salvageV6]

Here's a bunch more info. a searchable service manual link.
Section 8A-80 has the info. on the wiring connectors and troubleshooting. Parts 4 and 5 on the link.

Electronically Linked and Searchable Manual

 

[outatime86]

Here's a bunch more info. a searchable service manual link.
Section 8A-80 has the info. on the wiring connectors and troubleshooting. Parts 4 and 5 on the link.

Electronically Linked and Searchable Manual

What a great link!

 

[zapp240]

just a longshot, but my ecm/Sol fuse was blowing after startup due to a screw just to the left of the steering shaft right behind the wire harness bundle right behind driver valvle cover, sharp screw went right into harnes and pierced/shorted the black and pink wire. saw, earl brown had written a pst on the same issue. dremeled the screw odd and was good to go.

 

[Metacom]

Update: I remembered I plugged in the MAP sensor while changing plugs and kept it plugged in (has always been unplugged). Unplugged it and the fuse hasn’t blown…weird.

Guess I’ll tackle that issue once I iron in the rough idling and slight backfiring after changing the coil pack and module.

Thanks for the help all!

 

[RUQWKNF]

just a longshot, but my ecm/Sol fuse was blowing after startup due to a screw just to the left of the steering shaft right behind the wire harness bundle right behind driver valvle cover, sharp screw went right into harnes and pierced/shorted the black and pink wire. saw, earl brown had written a pst on the same issue. dremeled the screw odd and was good to go.

Back in "99, I had that exact same SOB screw cause me major fits, trying to diagnose blown fuse able links, on my White "87 Limited. You talk about pulling your hair out. Lawd have mercy! Late for work 4 days in a row as I was daily'ing it back then.
That stupid screw, has to be one of the most stupid things I've ever found on these cars over the years.
Must have been one of those guaranteed to fail items done to bring in more maintenance customers as the cars got older and out of warranty? Who knows.

I too tasked Mr. Dremel to fix that stupid screw once I found it, and fixed the wires it had cut into.
Somebody definitely needs to snap some pics and put them on here for everyone to see in the future.
It definitely could cause a fire if not addressed. With mine, on day 4 of repeated failure, I finally found the problem when I saw smoke from the wiring loom burning.

So, heads up to everyone out there, check that problem area asap.
Gonna go check Legend later this weekend.

Patrick

 

[salvageV6]

The digital dash cars have a round switch, actually two switches in one housing, no sensor for the two turbo lights in the dash. You may have shorted indicator bulbs or a bad flex board in the dash.

 

[zapp240]

Back in "99, I had that exact same SOB screw cause me major fits, trying to diagnose blown fuse able links, on my White "87 Limited. You talk about pulling your hair out. Lawd have mercy! Late for work 4 days in a row as I was daily'ing it back then.
That stupid screw, has to be one of the most stupid things I've ever found on these cars over the years.
Must have been one of those guaranteed to fail items done to bring in more maintenance customers as the cars got older and out of warranty? Who knows.

I too tasked Mr. Dremel to fix that stupid screw once I found it, and fixed the wires it had cut into.
Somebody definitely needs to snap some pics and put them on here for everyone to see in the future.
It definitely could cause a fire if not addressed. With mine, on day 4 of repeated failure, I finally found the problem when I saw smoke from the wiring loom burning.

So, heads up to everyone out there, check that problem area asap.
Gonna go check Legend later this weekend.

Patrick

Snapped a pic before it met Mr Dremmel, pierced right into the black oblong wiring loom. Fun part is it will be pot luck on what wire , or wires, it takes out.

 

[RUQWKNF]

Yup, there that SOB is.
Sick'em Mr. Dremel!
Sick'em!!!