Glow plug relay kills battery dead

   / Glow plug relay kills battery dead #1  

Highbeam

Super Member
Joined
Feb 9, 2005
Messages
5,039
Location
South Puget Sound, WA
Tractor
Kioti CK30HST
So I've had the unfortunate experience of getting all ready to run the tractor, sometimes after trailering it for 50 miles, and turning the key only to hear nothing. No clicks buzzes or lights. I have a 3 year old Optima style AGM battery and when I checked the voltage with my meter I got 0.20 or very dead. So I jump start the tractor with my truck or even a Honda car one time and everything works great, the battery recharges and the voltmeter reads 14 or so when running after I get back to the truck. The next day it will either start perfectly or it will be deader than heck.

The battery holds a charge when disconnected, the alternator charges just fine, and everything works fine when the tracor is running. I must have a short somewhere. So with the key out of the tractor and a fresh charge on the battery, I removed the ground cable from the battery and touched it back to get a satisfyingly large spark. Ah hah! I have a parasite, a leak, a short.

I've been having some glow plug issues over the winter where sometimes I get no GP action and the only thing other than a short that would suck so much juice is the GP system so I traced the GP wire from the head and it is a black wire with red stripe. I found the relay on the firewall with a black wire and red stripe and unplugged the relay. No more sparky at the battery terminal!

For peace of mind I think I'll do a little more testing on the tractor side of the relay plug to make sure that the GP timer is working right. The dash GP indicator always worked like normal. The GP relay plug was not corroded but was muddy inside which is odd since it is so far away from mud.

So is this a typical problem? The relay is easy to remove and replace, can't be too expensive. Does anyone have any other ideas or do you think I found it? On my Ford truck, the GP circuit draws 200 amps so I'm sure the GP system could drain a battery in short time on our tractors.

Oh and the Kioti starts up just fine without the GPs when it is 68 degrees out.
 
   / Glow plug relay kills battery dead #2  
Should be easy to verify if the relay is working properly. Assuming it's a "normally open" relay, there should be an open circuit measured with an ohm meter across the switching terminals when there is no control voltage on the coil. Then check the voltage on the control coil. There should be none with the key out. If there is voltage, then the GP relay would be closed as expected, measuring a short across the output terminals. In summary:

No control voltage, contacts open: problem likely someplace else

No control voltage, contacts shorted: bad relay

Control voltage when not expected, contacts shorted: timer, switch, or other relay that controls the GP coil voltage is the culprit.

Control voltage as expected, contacts shorted: problem is elsewhere.

Control voltage there, contacts open: shouldn't be the case with a "NO" relay. Indicative of a burned out coil.

You should be able to use jumpers straight from the battery to control that relay to see if it opens/closes as expected. The control coil should also measure low resistance (for all relays).

It strikes me that these relays could benefit from some surge protection, like diodes or at least a capacitor across the coil. High current surges and no suppression is what usually causes relays to fail prematurely. Sometimes you can buy relays with surge protection built in. Some relays might also have as separate Enable control line. But, I suspect that these do not.
 
   / Glow plug relay kills battery dead #3  
I believe that the contacts inside the relay are pitted and are sticking. You can put an ammeter in-line with the GP wire and see if it is drawing current. You can take a volt meter and see if you have voltage at the GP. in the off position. If so, the contacts are sticking together.
 
   / Glow plug relay kills battery dead #4  
Highbeam, I also use Optima Redtops in various vehicles and equipment and like them. However, I discovered they do not like to be discharged dead more than once or twice anymore than other-style batteries do. I have a current drain in my 79 CJ-5 somewhere that I could never catch/find so I installed a battery switch in line then replaced the Redtop. May or may not be solution for you.

When you are confident you have fixed the root cause, may want to replace the Optima and/or perhaps transfer it to a less critical piece of equipment.

RavensRoost
 
   / Glow plug relay kills battery dead
  • Thread Starter
#5  
Thanks for the responses. I have the relay out and on the bench. It is small and dainty, and doesn't seem up to the demands of the GP job.

I don't want to disconnect the battery every time because if the GPs are truly being constantly turned on then I would expect them to burn out or fail prematurely. Also, the load on the alternator would be excessive. The tractor is about the least critical piece of equipment I have and since I will always have my truck around I can always jump start it if needed. I had a 1974 CJ5 just after high school, loved that 304.

I believe that J_J has the answer. The relay is just gummed up and sometimes sticks on and sometimes sticks off. Sometimes it might work fine. I verified that with the GP relay installed, I was getting a huge draw on the battery. With the GP relay removed, I had no battery draw. I feel confident that the problem is in the GP system and the relay seems the most likely cause.

I can always use alligator clips and try to test the relay on the bench. I might do that. I read 64 ohms between the control circuit inputs which I expected since that load is from the coil. The relay terminals are labeled with numbers but I didn't write them down.
 
   / Glow plug relay kills battery dead #6  
I believe that J_J has the answer. The relay is just gummed up and sometimes sticks on and sometimes sticks off. Sometimes it might work fine. I verified that with the GP relay installed, I was getting a huge draw on the battery. With the GP relay removed, I had no battery draw. I feel confident that the problem is in the GP system and the relay seems the most likely cause.
The relay on my Mahindra did that. I wont trust another one - its a battery killer. I substituted a manual N/O switch.
larry
 
   / Glow plug relay kills battery dead
  • Thread Starter
#7  
To be fair, this one lasted 810 hours without a lick of trouble. If these relays were known to be junk then I would investigate one of the higher amp, and heavier duty automotive style GP relays. Those things are the size of a light bulb and rated for large continuous amperage loads.

If I don't hear any "Kioti Specfic" horror stories about these things then I'll just buy a replacement from Kioti. Sometimes a particular manufacturer specs out an improper part but that doesn't sound to be the issue here.
 
   / Glow plug relay kills battery dead #8  
Sticking contacts are classic signs that the relay would benefit greatly from a surge protection capacitor or a couple of diodes. The capacitor install is almost full proof. Simply place it accross the coil contacts. A cap. rated for about 24V or above would work. Value isn't so important. This will keep arc-generated gunk from building up on the contacts and the relay will last many times longer. Cheap and easy add on available at radio shack.

Relay function is pretty easy to verify. But, it could be something else, like a stuck timer or switch. Did you verify that you had no voltage on the control coil, but were still drawing current (had a voltage) at the relay output?
 
   / Glow plug relay kills battery dead #9  
Sticking contacts are classic signs that the relay would benefit greatly from a surge protection capacitor or a couple of diodes. The capacitor install is almost full proof. Simply place it accross the coil contacts. A cap. rated for about 24V or above would work. Value isn't so important. This will keep arc-generated gunk from building up on the contacts and the relay will last many times longer. Cheap and easy add on available at radio shack.

Relay function is pretty easy to verify. But, it could be something else, like a stuck timer or switch. Did you verify that you had no voltage on the control coil, but were still drawing current (had a voltage) at the relay output?
Good idea, but be sure to put it across the relay contacts and not the coil. The arcing is across the contacts rather than the "pull in" coil.
larry
 
   / Glow plug relay kills battery dead
  • Thread Starter
#10  
This is one of those relays that by plugging it in, the contacts are all concealed. Not posts on top like on a starter relay. I was able to verify that the control voltage was not present with tractor off by probing the relay connector on the tractor side. When I tested the relay itself on the bench after removal the contacts acted normal meaning the load contacts were not connected and the control contacts had 64 ohms of resistance across them. If I get a chance I can apply 12 volts to the control lead and move the coil back and forth which should make a nice click.

If this was a monthly or even semiannual problem then I would look into fixing it with a capacitor or with a stouter relay but once in 4 years is probably not a big enough deal. I like to stick with OEM as much as possible.

If replacing the cheap relay doesn't fix the GP issue then I will need to dig deeper, possibly into the timer control. The relay is super easy to swap out.
 
 
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