2 questions - what might cause...

[mvtofino]

...a relatively new (only a couple months old) Glow Plug Relay to fail? I'm trying to sort out some of the wiring in my motor-home's starting & glow plug circuitry that previous owners had their way with.

Also, why would the engine continue running when the key is turned to the "off" position? I've had to install a toggle switch in the injector pump's fuel shut-off solenoid circuit in order to stop the engine running. Great back-up security system, but what might have gone wrong with its wiring that permits it to keep running?

Thanks for any help or suggestions.

JT

[trbankii]

On the relay, always a chance that it was a dud from new - not enough solder someplace or a component overheated during assembly or whatever. Typically I find electronics to fail (other than from outside abuse) either relatively early in their life from manufacturing defects or after years of service.

As for the second, it sounds like you've found the issue - that the shut-off solenoid isn't energizing (de-energizing?) on shut down. Question is why. You say the PO had their way with the glow plug wiring. Could they have hacked up other wiring harnesses as well?

Douglas Adams' quote often comes to mind when dealing with POs...


"A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools."

– Douglas Adams, author (1952 – 2001)

[mvtofino]

...here! here! Mr. Adams seems to have nailed it squarely on the head! Makes me think about the many times I've been someone's "previous owner"...

No doubt there has been some degree of harness manipulation in the past, but tracing all those wires is a daunting task well beyond my knowledge or skill level. I have tried to restore things back to stock whenever possible, and when not possible I try to make an informed decision on how things should be wired - theoretically, that is - and hope for the best. I am slow and methodical when it comes to wiring, and I am usually happy with the result. Usually.

The most recent discovery was an apparent duplication of a G/P relay bypass switch. Thought I had it sorted out, but then I found yet another 10-12 AWG wire from the G/P relay's control circuit to battery positive with a 30 amp circuit breaker installed inline. This wire is in addition to the dual blade connector installed at the factory (the wires go into a large harness to where???)

I was wondering if a duplication of the relay's control wiring could cause the relay to fail. The way it looks to me right now is the control circuit is energized 100% of the time, however the glow plugs only come on when one of the two bypass momentary switches is pressed (yes there are 2 wired in...). If that is true, would it ultimately fry the relay? (maybe not right away, but after a period of time being energized 100% of the time).

I have another brand new G/P relay to install this afternoon. I plan to scrap the existing dual blade connector and its wires, and run a fresh 10-12 AWG wire from battery positive to the manual bypass momentary switch through a new 20 amp, inline circuit breaker to one side of the G/P relay's control circuit connector (one of the two male blade terminals), and the other side of the relay's control circuit to a good ground. That should be a simple solution to operating the glow plugs in future.

A PO had hotwired the G/P controller through the RV's emergency start switch on the dash which I didn't discover until very recently. The new controller that I installed a short while ago fried up shortly after being installed which is why I had a dealership (while on vacation highway) install the bypass switch. They installed the existing G/P relay at the same time because I didn't want one weak component in the GP circuit; everything else has been replaced except the wiring harness itself. So much for careful, preventive planning! If they had checked the system out properly first, they would have known a bypass switch had already been installed, and I would have saved $900 USF and many, many, many hours of frustration.

I just want this very expensive learning curve to end. Sorry for such a long message, but I don't know how to explain what has taken place with any fewer words.

Thanks for your suggestions and input - please keep them coming!

JT