Electrical problem, fuse keeps blowing

[sveckan]

Hi,

Please take a look at the attached picture, can you tell me what that fuse(?) is that I've marked with at circle? In my DIno it's replaced with a standard 10 amp fuse. I've looked at the wiring diagram but can't figure out what it is. The problem is, when I turn on the ignition, that fuse blow and I'm not sure if that is a small or big problem...

Thanks!

Kind regards,
Anders Svensson, Sweden

[ThomasK]

I drive since 6 years without this fuse (when I remebder correct the white wires are linked together). Don´t know what this is for, I suppose for the vacuum pump, as this is also not part of the wiring diagram. KR, Thomas

[alh]

I drive since 6 years without this fuse (when I remebder correct the white wires are linked together). Don´t know what this is for, I suppose for the vacuum pump, as this is also not part of the wiring diagram. KR, Thomas

That would explain it, haven't found anything in the wiring diagram with two bianco wires attached.

[Tobi]

I just had a quick look at my car. I still have this fuse connected (I didn't knew that this is a fuse). One of the two wires seems to go to the bulkhead and the other into a relay just around the corner of the bulkhead. This relay has also blue and black/blue wires. I also don't have a clue of the function.

[Dario]

The fuse and relay provide current for the vacuum pump for the brake servo. Normally, with the engine in operation, there is enough manifold vacuum and the pump is off thanks to a vacuum sensor (there is a small screw in the back for adjusting the cut-off, behind the rubber cap). It's there in case you loose engine power while driving. If it keeps blowing, check the relay and pump!

Dario

[sveckan]

The fuse and relay provide current for the vacuum pump for the brake servo. Normally, with the engine in operation, there is enough manifold vacuum and the pump is off thanks to a vacuum sensor (there is a small screw in the back for adjusting the cut-off, behind the rubber cap). It's there in case you loose engine power while driving. If it keeps blowing, check the relay and pump!

Dario

Many thanks! I'll check that.

/Anders

[Dinoswede]

Hi. everybody!
I think I know what the discussed "fuse" is for. It is a safety cut-off switch, according to the Fiat original spare parts list (no 4235474). In the wiring diagram it has
no 73. It is supposed to protect the vacuum pump to break down in overheating, caused by a leak in the vacuum tubing and servo system. Normally, if the system
is without leaks, the vacuum sensor (no 4216460) starts the vacuum pump if the vacuum pressure is too low, and cuts the power off when it reaches normal value.
If a leak somewhere in the system letting air in, the pump will obviously start, trying to compensate for the vacuum loss. But the vacuum pump will get very hot
after a while, so for protection, the discussed cut-off switch will stop the pump after some 10 seconds or so.
I have personal experience of this. I owned a 2,4 Coupe during the 80´s, and I once noticed a humming noise, that I did not recognized. It was the vacuum pump
going on and off, in short periods of 10 seconds, because of an air leak in a hose. The cut-off switch did its job, but I can assure you all - the vacuum pump was
VERY hot!
Dinoswede

[ThomasK]

Hi, this is great - thanks Dinoswede for sharing your experience. As I was wondering since a long time what the fuse is for and how this in original really was intended to work.

You mention a wiring diagram where the wiring related to the pump and also the pump and the switch is included. Can you make a photo or even better scan this section and post it here?

Would be great, thx a lot in advance, Thomas

[Dinoswede]

Hi, Thomask (and all other Dino owners)! I have noticed there are several electrical diagrams in the LIbrary, already, but I have so far not found any diagram
showing the 2,4 Dinos with the vacuum pump and relay included. It seems like they all are 2,0 Litres electric diagrams (?) , but I am not sure enough to tell
the exact differences between these two - only that the discussed vacuum pump and relay are missing. At one of the diagrams, you can see the Fiat and Dino
logotypes without the "2400". As far as I know, Fiat was very keen putting the "2400" logotype on all official books and brochures, when the upgrade was made.
However, in the Specifications and Features" for the 2400 I have. with the typical two diagrams - for the Coupe resp. the Spider -the different components
are not numbered in the same way, which does not help, of course. Furthermore, no wiring colour codes are shown.
I have tried to download these electrical diagrams from the book to this site, but as my skills in computer technics are close to zero, I need a description step
by step to manage doing that - in short - I haven´t a clue... Perhaps it is easier for me putting these pictures directly in the Library??

Dinoswede

[doublegarage]

Does anybody know of a modern version of this "motor-protector" that could be purchased and adapted for use in the Dino? I imagine it's some sort of "bimetal strip" device (like a flasher relay but with far different properties) that heats up, disconnects, cools, reconnects etc. I've never seen one for a motor, however.

This circuit is the worst aspect of my Dino's electrics - the motor seems to require very heavy current, and draws it from a circuit that includes the fuel pump, which is susceptible to voltage drops - I'm thinking of re-wiring with a separate fuse. or disconnecting altogether.

Dinoswede, if you PM me an email address I will reply, you can send me your diagrams and I will try to post them in the library for you.

-Richard