Hi Bob,
I believe that the original "condensers" are of the non polarized paper
variety & wouldn't require reversing.
SU apparently decided that the diode was a better arc suppression device
& installed them in place of condensers on later models. As you say, a
three amp 50 PIV rated diode could be installed in place of the condenser.
More simple to wire would be the Moss replacement diode with flexible
pigtails. The heavy conventional diode leads are a bit hard to get wound
around the small terminals. It would be Moss #377-135 for positive
ground & #377-145 for negative ground. I'm sure that Burlen has
equivalent diodes.
For that matter, the original condenser will likely work pretty well as is.
One thing I have noted when reversing battery polarity is that "some"
light current electrical contacts seem to build a polarity sensitive
"film" that won't let them conduct when the polarity is reversed & may
need to be cleaned. The turn signal relay contacts come to mind.
Regards,
Dave Russell
BN2
Bob Spidell wrote:
> Simon,
>
> I THINK the condensor (capacitor) is an electrolytic. If you keep
> it, you'll have to reverse the leads, else the first time you apply
> current you'll fry it (probably to a dead short, and possibly cause
> damage to your wiring). If it's any other type, it won't hurt to
> reverse it.
>
> I've used "off-the-shelf;" i.e. standard diodes, with success.
> There's not much point in using a Zener--aka "avalance"--diode;
> they're used for overvoltage protection which you're not likely to
> experience. You'll need one with a quite high current rating (at
> least 3 amps@, say, 20+volts). Make sure you get the polarity
> correct--diodes usually have a silver paint "band" on the anode (+)
> side (Dave R, correct me if I'm wrong here ;) FWIW, this is called a
> "flywheel" diode and is common on a lot of inductive loads (like
> relays).
>
> If it's not too much jack, I'd probably get one from SU ... they come
> with terminals attached and the leads should be marked red (+) and
> black (-). Make sure you tell them it's for negaive ground (though
> it won't matter if you get the leads correct, the terminals and leads
> might be a little different).
>
>
> bs
>
>
> Simon Lachlan wrote:
>
>> Hi,
>>
>> I have a MkII BT7, which is not particularly relevant here as it
>> has an AUF301 SU fuel pump which my manual says is from the "Later
>> convertible model MarkIII".
>>
>> I have the pump in front of me as I type. It has a condenser (item
>> 25 on page DDD.13 if you've got the same hymn sheet as me).
>>
>> So, when I take the car from positive to negative earth, what do I
>> do to the pump?
>>
>> I've dug through my collated info on this topic and the collected
>> wisdom is a bit contradictory:-
>>
>> 1) Leave as is, but switch the leads around. Is that only for
>> pumps with diodes fitted instead of condensers?
>>
>> 2) Leave as is.
>>
>> 3) Replace condenser with a diode.
>>
>> 4) Replace condenser with Zener 20-28 volt diode.
>>
>> 5) Fit a diode, CSX1004, is what Burlen Fuels (the SU people
>> in UK) say. I suspect that they are just saying "Send money, NOW"
>> but being polite.
>>
>>
>>
>> Maybe a CZX1004 is a Zener???
>>
>>
>>
>> What's to do here?
>>
>>
>>
>> Thanks,
>>
>> Simon.
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