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Old 22-09-2013, 19:05   #1
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Hotwire motor with clothespin

To start my motor I now need to clamp a relay closed using a wooden clothespin. (I'll pause a moment while you laugh... )

May I ask for some advice/opinions?

Setting the stage: That relay is part of the electronic control box and allows power to the glow plugs. Once the motor cranks over and starts I remove the clothespin & normality returns. If the motor is warm, then no little tricks are required. (The control box also acts upon over temp and/or low oil pressure alarms, etc.) This problem only recently surfaced. No motor maintenance was performed between "it works" and "it doesn't work".

Left to it's own actions during the start cycle there's approx 3.5 vdc seen on the relay contact's output leg; the motor cranks but doesn't start.

With clothespin applied, it becomes battery-level power (13.whatever vdc) seen on the relay contact's output leg; ; the motor cranks and starts.

During my testing, I disconnected the relay's output wire and then temporarily ran a separate 10 AWG wire off a 30 amp ckt bkr to the glow plugs. With that breaker acting as a "relay", all worked fine.

I'm unable to determine if there is insufficient current to hold the relay closed, or if the relay itself is faulty. I've tried cleaning the relay contacts with emery cloth, to no avail. Swapping out the glow plugs with a new set makes no difference.

IF there were a handy-dandy electronics shop around then I'd just start replacing parts beginning with the relay, but I'd be winging it. There are no markings on the components that I can see to indicate part numbers or mfr. And I'm leery of arbitrarily installing just any-old-relay due to the amount of current the plugs apparently require.

It's a Lehman/Peugeot marine-modified 4-cyl/60HP diesel motor, installed in '87, and there doesn't appear to be much tech help available. At least on-line. So far, I've been unable to locate electronic schematics for this little box. My owner's manual doesn't delve into electronic details.

To clarify, this is not the starter solenoid I'm talking about but a relay who's only apparent (to me) purpose is to provide power to the glow plugs. (And that the motor demands active glow plugs here at 15 degrees South is a different topic.)

On the one hand, it's a great anti-theft system ; on the other hand, this could be a PITA should a 2AM re-anchor maneuver come about.

Advice? Suggestions? Opinions?

James
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Old 22-09-2013, 19:48   #2
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Re: Hotwire motor with clothespin

Sounds like the contacts in the relay might be a bit pitted. Using the clothespin tightens the contacts. Might be able to pull the cover and file the contacts with a points file. Probably best to just replace the relay. A $10-$15 car headlamp relay would be a good fit if the original model is hard to find. Actually a manual switch would work in a pinch, like the breaker.
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Old 22-09-2013, 20:04   #3
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Re: Hotwire motor with clothespin

if the weather is warm, glow plugs are not needed.
disconnect them.
run the start button wire direct to the starter solenoid.
the magnet in a relay can weaken with time, and heat. this will give a poor connection.
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Old 22-09-2013, 20:31   #4
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Re: Hotwire motor with clothespin

I'll second Sailorchic's recommendation. For a quicky fix, open the relay and use that emery cloth on the points but it could be the coils that engergize the relay aren't holding the points together.

However at the end of the day, a relay is a relay. Get one that activates with 12V (assuming your boat is 12V system) and sufficient capacity to handle the current the glow plugs draw.

I think a typical glow plug will draw 12-18 amps. So if you have a four cylinder then 4 X 18 to get the current capacity for the relay. I would upsize a little just in case.
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