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Electrical drain MSD ?
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gitchesum
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PostPosted: Tue Sep 18, 2018 5:51 pm    Post subject: Electrical drain MSD ? Reply with quote

So I recently picked up a car with an MSD. If the vehicle sits more than 3 days , the battery is drained. Does the MSD use power just sitting ? Here's what I know.
Replaced battery and tested alternator ...both excellent.
If I pull the ground cable off after running I can put a test light on the neg cable end and the positive terminal, and it shows a draw, but dims to nothing after 2 minutes.
With the engine running, I can pull the neg cable and it will continue to run, assuming it's running of the alternator, but doesn't the neg cable have to be hooked up ?
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air-h2o-air
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PostPosted: Tue Sep 18, 2018 7:05 pm    Post subject: Re: Electrical drain MSD ? Reply with quote

msd should not have any draw on battery when car is shut off
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Dale M.
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PostPosted: Tue Sep 18, 2018 7:13 pm    Post subject: Re: Electrical drain MSD ? Reply with quote

No negative cable does not have to be hooked up to keep vehicle running because alternator or generator produces the 6 or 12 volt and alternator or generator body is return path or ground....Thusly being the source for all power in vehicle....

Basically a battery is only a "stored power source" to spin up starter and produce enough power to fire ignition, once car starts, the generator or alternator is prime source of sustaining vehicle power.... Battery will also be there to supply power if generator or alternator fails or can not meet demand of cars "systems" (ginormous power eating stereo), but for short period of time depending on how good battery quality and state of charge is.... Battery can also act as a electrical system noise filter to some extent...

It's been said disconnecting the battery while engine running will cause the alternator to blow, I have not witnesses it maybe some have, but why push your luck... Don't do it...

The MSD should not cause a power drain, if you think so disconnect it alone from battery and monitor results... IF MSD unit is draining your battery then unit has a problem...

Generally if there is a drain, procedure is to put a volt or ammeter or test light between disconnect battery cable and battery terminal and remove fuses or disconnect accessories till indicated drain goes away, last item disconnected before indication of drain stops is probably culprit...

Dale
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Last edited by Dale M. on Wed Sep 19, 2018 7:17 am; edited 2 times in total
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mcmscott
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PostPosted: Tue Sep 18, 2018 7:28 pm    Post subject: Re: Electrical drain MSD ? Reply with quote

MSD installed correct will not cause a parasitic drain.
An alternator cannot produce both polaritys at the same time! It is a physical impossiblity!
And I have seen multiple alternators destroyed by dissconnecting the battery with the engine running!
If the alternator sees no voltage (no battery) then the regulator will close to produce maximum voltage and kill itself! Any one with half a brain can understand this!
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gitchesum
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PostPosted: Wed Sep 19, 2018 7:19 am    Post subject: Re: Electrical drain MSD ? Reply with quote

The part that gets me is that I can disconnect the neg cable , hook up a test light to the neg cable and the batt pos terminal and the light comes on, and stay lit for maybe 1 minute, then slowly goes out.

Like a residual drain from somewhere.
Tried leaving the cable connected and pulling 1 fuse at a time with no results.
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61 356B
73 The Thing w/2276, and more.
Honda XLR 250, 69 Z50, Yamaha 100 Enduro...and others.
GMC SLT 4x4 Dmax
Kubota L3710, not enuf attachments.
And various VW's that come and go...
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tattooed_pariah
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PostPosted: Wed Sep 19, 2018 7:23 am    Post subject: Re: Electrical drain MSD ? Reply with quote

I'd start by looking for things that didn't come from the factory..

If the PO put an MSD box in it, they probably added some other stuff, and it could just be something not wired properly,or something wired to a circuit that's hot all the time, but doesn't need to be..

for example, in my car, I like being able to listen to music without the keys in it, so I always wire my stereo to an always hot circuit, but if i forget to pull my faceplate off when i get out, it'll run down my battery..
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Dale M.
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PostPosted: Wed Sep 19, 2018 7:36 am    Post subject: Re: Electrical drain MSD ? Reply with quote

gitchesum wrote:
The part that gets me is that I can disconnect the neg cable , hook up a test light to the neg cable and the batt pos terminal and the light comes on, and stay lit for maybe 1 minute, then slowly goes out.

Like a residual drain from somewhere.
Tried leaving the cable connected and pulling 1 fuse at a time with no results.


Your test tools (meter or light) should connect between negative battery cable and negative battery post (with cable disconnected)... You are looking for either a constant voltage or a current flow (amperage) with meter or lamp staying lit if using test lamp, that indicates a drain on battery.... If no voltage reading or current reading or lamp does not light then there is no drain on battery with all vehicle systems off... The test you trying to use is not correct procedure and probable giving you a false indication if problem...

Dale
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gitchesum
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PostPosted: Wed Sep 19, 2018 12:30 pm    Post subject: Re: Electrical drain MSD ? Reply with quote

Thanks guys....good tips.
I'll look at that and see what I can find.
Thanks again.
C
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Looking for SP Kadron manifolds...please !!



57 SC
61SC
68DC
61 rag w/356B brakes
61 356B
73 The Thing w/2276, and more.
Honda XLR 250, 69 Z50, Yamaha 100 Enduro...and others.
GMC SLT 4x4 Dmax
Kubota L3710, not enuf attachments.
And various VW's that come and go...
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
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