| Author |
Message |
Austin Davis (Zimtok)
Registered Member
Username: Zimtok
Post Number: 20
Registered: 9-2006
Posted From: 63.94.78.194
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, October 09, 2006 - 8:54 am: | |
I have a problem where my engine control relay is staying energized when I turn off the switch to shut the engine down.
Here is what I've traced it down to so far:
When the relay is stuck, the dash switch is off, I can read about 9vdc at the terminal from the switch. (with the wire removed from the terminal)
With it stuck I remove each wire one at a time and find that removing the "BAT" terminal wire it released the relay. With that wire off the relay energizes and releases every time with the switch.
My conclusion:
With some corrosion apparent around the rivets holding the relay terminals on the base, I think voltage is leaking from the "BAT" terminal through to the switch wire terminal. It's not enough at 9vdc to pull the relay in but it is enough to hold it in after it is energized by the 12vdc from the switch.
Can I still buy this relay? OR do I need to drill out the rivets, clean it up, and reassemble it? |
Craig (Ceieio)
Registered Member
Username: Ceieio
Post Number: 271
Registered: 12-2004
Posted From: 207.101.213.58
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, October 09, 2006 - 4:40 pm: | |
Austin - first of all I know nothing about the circuit on your bus!
My experience with older vehicles (my MCI included) leads me to start looking at failed grounds first when I have electrical problems.
Clean connections, look for corroded wires, clean grounding points etc. and see where that gets you.
As to your thoery of current leaking, if you can isolate the relay connections from the bus wiring, an ohm meter should tell you if you have a high impednace connection problem.
Set your meter to the highest measurement scale and measure. You should get and infinite reading (or zeros on a digital meter). If not, then you do have a current bleed of some kind. (if you cannot get the relay islolated, then the results of this test are invalid).
HTH
Craig - MC7 Oregon |
Tom Caffrey (Pvcces)
Registered Member
Username: Pvcces
Post Number: 999
Registered: 5-2001
Posted From: 65.74.65.54
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, October 09, 2006 - 9:32 pm: | |
Austin, check with Luke at US Coach. The number is (888) 262-2434. He can tell you what is available.
Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska |
Tim Strommen (Tim_strommen)
Registered Member
Username: Tim_strommen
Post Number: 240
Registered: 11-2004
Posted From: 64.186.173.26
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, October 10, 2006 - 8:16 pm: | |
Austin,
From how you describe it - it sounds like there is a short inside the corroded relay that is leaking power from the supply of the shut-down solenoid. This would be one reason why you have voltage despite the switch input wire being disconnected.
I agree that you should also look for bad grounds – with spike isolation resistors in-line with some of these devices, you could be back feeding the supply to the coil from another source.
I’d recommend pulling the relay and ensuring that there is no cross connection from the controlled coil to the actuated circuit in the relay first – then once you have ruled out the relay (or singled it out – which ever is the case), look at the voltage potential from the ground at the panel to a freshly driven screw (into the local frame) to see if there is a significant ground potential (if it's more than ~.1 volts within a foot of the electrical panel - there's definately a ground problem).
From my experience with car audio – if there more than 6VDC at a 12volt coil that is energized, it will likely stay actuated (on). Most 12volt coils need a hair more than 9volts to switch on (the 12 volts is just good design headroom and power dissipation characteristics).
Just so you know, you don’t need to replace a relay with the exact same part (it’s just good practice), but you do need to try to match the design limits of the original device (coil ratings: impedance, voltage, and duty cycle – and contact ratings: voltage, current temperature). You may be able to find a high quality replacement without dropping >$40 on a relay (just a thought – do it your way). Also, if the relay doesn't have a clamping diode across the coil (many new relays have them built-in), I'd recommend installing one (again good practice).
Cheers!
-Tim |
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