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Found Diode Fuse in back comp of 308 by the Jetronic ECU for the QV Is it a fuse

3331 Views 13 Replies 0 Participants Last post by  Richelson
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I found this little black roun

I found this little black round Bosch part that isn't in my owners manual but is in my parts manual as a fuse. My schematic calls it a diode. JRV what do you think? It gets power from the cold start fuse in the fuse block. It is about one inch long and is a Bosch part. I checked continuity accross it and nothing. So can I replace it with a fuse? Thanks.
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I looked it up online and it s

I looked it up online and it said Magneto. What is a Magneto. Looks like a fuse holder but when I opened it up, it is a sealed unit but I opened it. I am not sure what it is.
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Rich,

If the device is trul


Rich,

If the device is truly a diode...which only allows current to flow in one direction...try checking continuity by reversing the probes on your ohmmeter. If the diode is functioning correctly, one way will read an open circuit, the other will read continuity.

Regards,
David
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Yes I have no continuity. It

Yes I have no continuity. It is strange. My parts books say fuse but it isn't at all. Would putting a fuse in its place be ok like my parts book shows. (3A is what it shows)
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Here is a pic. Why was a diod

Here is a pic. Why was a diode used? How come 84 QVs have fuses?
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Rich,

there is a reason the


Rich,

there is a reason there is a diode in the circuit. I'll guess it's to prevent tripping the relay too soon. Go to Radio Shack or order from Ferrari an exact replacement.

Where did you find this Diode?

Regards, JRV
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It is in the right rear compar

It is in the right rear compartment where the Jetronic box is. Is says in one schematic I have that it is a diode protection for oxygen sensor. I went to radio shack but can't make out the rest of the #'s on the diode so I am not sure V to get it for.
The strange thing is that the 84' QV uses a fuse instead of the diode.
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Rich,

In this particular ap


Rich,

In this particular application, the "voltage" of the diode really doesn't make any difference. The voltage rating on a diode refers to voltage at which it will "break down"...In plain English, the voltage at which it will flow current in the reverse direction. Just think of a diode as a one-way valve...

Regards,
David
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Got it. Just for some more in

Got it. Just for some more info I looked in the schematic. The diode seems like it is protecting the cold start injector relay, before that is the csi fuse then before that it goes through the efficiency a/c relay in the front compartment. I will go out and pick one up and solder it in.
I am just still a little perplexed on why they used a diode here and not on the other 308QVs. Is it to stop the CSI Injector relay from tripping at off times like JRV was alluding to and does it serve another purpose? Thanks for the info guys. I appreciate it.
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Here is a pic of the casing to

Here is a pic of the casing together just thought some would like to see.
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Rich,

are you saying the e


Rich,

are you saying the earlier car had a fuse and the later cars have a diode?
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Yes

Yes
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Then the fuse was an experimen

Then the fuse was an experiment that failed, when they realized the mistake they updated the system to a diode.

Make sure you reinstall the diode in the correct direction for flow.
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Ok, thanks. I am going to get

Ok, thanks. I am going to get one and install it.
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