Fuse blowing: Air pump/turn signal/glass lifter/rad fan relay

You mentioned a lot there. I'm going to comment on one small item - I believe that some of the "newer" cars had the brake light show if there was low fluid. It doesn't make sense that that would occur after a fuse blows, but you might want to check the brake fluid level.

 

Unfortunately, the pdf copy that I have of Angelo Wallace's translation of the 246GT/GTS Workshop Manual is of such poor quality that the schematics are virtually unusable. If you can get me a better copy of the schematic shown on page 56 (which I think is for a US 246 since it has the air injection pump) or some other readable copy of a schematic for your car, I'd be glad to give it a look over.

 

Greg

Wiring issues on the Dino are a nightmare but can be easily solved by working in a logical manner. First step is isolate the problem fuse and check for short circuit in the wiring. Disconnect each component in turn served by the fuse and find out which one is the culprit.

Here is a coloured wiring diagram produced by Adrian Le Hanne, very useful to get blown up to A3, may not be applicable in all cars as they changed over the years but its a good starting point. It does contain some minor errors but on the whole its very good.

One thing that does concern me is the high charging rate, you could have a big issue here if its not solved. The ammeter wiring runs through the main loom and at the sustained charging the wires will get hot and melt. There are lots of posts on this, use the search function to find them, I had similar problems in this area and it was a few items causing it, bad electrical connections, earthing and voltage regulator.

Tony

 

Yes, please try again in pdf, if possible -- being able to resolve the very small item numbers is what's important (like the tiny item numbers for the various warning lights in the tach and speedo). That does look hopeful as being the right schematic for a US 246.

That might help some if they use the same numbers for the various item, but I think it is for a different Dino -- not only is there no air pump in the item list (it may be there and not labeled), but there's no parking brake warning light switch nor parking brake warning light shown (The Wallace translation has ~5 schematics in it, IIRC, and none are clearly labeled for which Dino they are for). Since Greg reports some very strange behavior from the parking brake warning light, it may be the best thing to look at for how that could even happen (in the typical parking brake warning light architecture, having any upstream problem cause that symptom is near impossible -- so the 246 parking brake warning light wiring design must be something pretty strange/untypical).

+1 -- it's like the ammeter and alternator behavior are just confirming that there's a huge short somewhere.

 

Perfect! Please give me a day, or so, to have a look.

 

The charging issue could be a easy fix and yes dont drive until resolved. Mine was a cumulation of bad bulkhead / firewall fuse block & connections. In the end I rewired that circuit with upgrade wiring and never had a problem since.

These wires can get very hot if its not dealt with, as they run in the main harness it could have shorted out.

Tony

 

OK, the bad news is that the 246 schematic that you posted does not have a single fuse running the items in your thread title (and it seems to have some serious wiring errors on it, but it doesn't matter because we won't use it). The good news is that I (remembered that I) have a copy of the 60/72 OM Supplement for 1973 US 246, and the schematic in it does have a single fuse running all of the items in your thread title -- copy attached (although it also seems to have some wiring weirdness on it, too). My first advice is to find relay item "89-Safety belt electric circuit relay (SIPEA T10-12S)" and unplug it and see if your parking brake warning light then works correctly (unfortunately, unlike later F OM, there doesn't seem to be any diagram in 60/72 describing the relay locations) -- i.e.,

key "on", engine not running, parking brake "off" = parking brake warning light "off"

key "on", engine not running, parking brake "on" = parking brake warning light "on"

You might also give a little shake to (the unplugged) relay 89 to hear if anything is broken and rattling around inside. If the parking brake warning light behavior is still bad with relay 89 unplugged, give a shout back, and I'll try digging deeper. If all is good with the parking brake warning light behavior with that relay 89 unplugged, see if the ammeter is now better behaved (and/or if that same fuse blows) when the engine is running.

 

No, no change to the course of action, but it might change what "OK" behavior is -- maybe "OK" should be the parking brake warning light not illuminating when it shouldn't and the fuse not blowing (rather than the parking brake warning light being "on" when it should be "on").

The "switch" in the parking brake lever mechanism is usually a very crude thing that can get bent up and malfunction (either "on" when it shouldn't or not "on" when it should), but no matter what's wrong with it, it should never blow a fuse.

 

I shouldn't have written "unplug relay 89" so casually. I should've written "unplug the wires from relay 89, carefully marking which terminal that they are connected to" and that you'd have to unbolt it to give it a shake -- I forgot that your model does not have relay sockets.

Another question: Is your unfastened safety belts warning light and/or buzzer working correctly or not?

 

You must have more "undone/not working" than that -- that plug on the passenger side seat is just for the passenger side (there is a switch in the seat itself to detect if a person is there and a switch in the seatbelt receiver to detect if the seatbelt end is plugged in, or not) -- the Driver's side also has (different) switches working in parallel to activate the unfastened seatbelt warning light/buzzer. Not surprised if it's been disabled (as the buzzer is quite annoying ), but can also be a sign that something is wrong with relay 89 and/or a modification was done poorly. The best way to disable the unfastened seatbelt system IMO is just keep relay 89 unplugged -- only the unfastened seatbelt system will not work -- the parking brake warning light system should still work OK (but you stated you have something already wrong there, too). Will await your report.

The placement of relay 89 on the 60/72 schematic indicates that it is located with most of the other relays.

 

The descriptions at Maranello Concessionaries for TAV 116 suggest that it is the 11 (USA) relay on TAV 116:

https://www.ferrariparts.co.uk/diagram/ferrari/246-dino-gt-coupe-spyder-(from-ch-02132)/116-fuses-and-relays

because:

2U = brake warning relay (so not this)
6U = A/C relay (so not this)
11U = relay (has to be this by process of elimination)

Another sanity check would be to measure the resistance from terminal 87 to terminal 30/51 on the unplugged relay 89 (relay 11U) = should be 0 Ohms when the relay is unenergized (i.e., a normally-closed relay). Although Sipea T-5220 (a normally-open relay per my internet searches) seems like not the right relay for relay 89 (and, unfortunately, the pictures of relay 11U on the Maranello Concessionaires website show no markings at all) - but might explain your unfastened seatbelt warning system not working if someone used the wrong relay.

Make sure you note which wire color goes to which terminal on the relay (the terminal numbers should be shown on the relay) -- the 246 schematic not showing the wire colors is a real negative.

 

I just checked my '74 GTS and the #11 relay is a T5170. Pretty sure it is original.

 

Use oldtimer's method - Tony said logical way, not random way

Go to fusebox and find your blow fuse.
See the big wire enter from one side to fuse, ID that is the power supply
See the other side of fuse with 5 wires - those are the circuits using power

Use a flat head screwdriver and loosen the wire connection at the fuse circuits, then remove one wire (only one please) from the circuits, tighten screw to secure 4 remaining wires then drive and do the thing that blows fuse.

If fuse does not blow then the circuit you disconnected holds the short. Track it down by following downstream.
If fuse does blow then it is still one of the four remaining, so remove one more wire and repeat until circuit is isolated.

Once you find the circuit that blows to short, follow it and trace each location for the failed part.

 

Does your unfastened seat belt warning light and buzzer system work correctly? (My quicky internet search shows that that is also a normally-open relay; whereas, the 60/72 schematic shows relay 89 is a normally-closed relay.)

 

All of the components are there but were disconnected when I got the car in '84 and I never tried to test it. I will at some point just to make sure it works.