Interesting glow plug controller card failure.

MarcusOReallyus

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Well, it seems my GP controller card has died. I haven't yet double checked to make sure the blue wire is still good, but if that checks out, it's the card.

I'm a little handicapped on working on it, since I have a busted knee at the moment. I had a 55mph encounter with a 90s-era Suburban, and lost.

Anyway, this leaves me sending one of my boys to do testing for me while I sit in my easy chair. After a while, I start feeling sorry for them and didn't want to send one of them out to test the blue wire. I'll do that next week.

Meanwhile, I got a look at my controller card and I don't see any of the usual failures I have heard described. What I found is what appears to be a previously repaired trace.

If I'm not mistaken, this trace is the ground for the card, connecting to the two black wires on the end of the connector.

Can someone confirm that?

(By the way, I'm hosting this off site because I have been unable to upload pictures for a few weeks. Dunno why.)

 

Bighorn

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The glow plug controller supplys ground to the glow plug solenoid.
If you think about it; what would cause that trace to get hot?
I would suspect a problem elsewhere as well as the card.
Such as corroded grounds, a short in the wiring, glow plug solenoid problem.
Would be a shame to replace the card and still have the issue that caused the failure.
 

MarcusOReallyus

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Looks like it is if it goes to the bottom edge connector of the card.
Yes, I've gotten another picture and confirmed that it is the ground trace.



The glow plug controller supplys ground to the glow plug solenoid.
If you think about it; what would cause that trace to get hot?
Yes, I'm aware of how it works. There's only one thing that would cause a conductor to overheat, and that's too much current.

This looks to me like a previous repair, and I have heard more than one similar failure. I've also heard of burned chips and the usual failed capacitors. I don't see any of that here.

Antennaclimber, what's your take on the most common failure mode for these cards?

If a burned ground trace is common, it seems to me that the design is poor. The GP relay coil is allowing more current than the card can handle over time. AC, do you know the current draw for the GP coil? I'm guessing it's in the 1 amp neighborhood. I can't find specs online, and testing is a pain in the leg right now.

If that's the case, a resistor inline might solve the problem, but may cause unreliable operation of the relay.

Another solution would be to put a standard automotive relay in line with the light blue wire. Let the controller provide ground for that smaller relay (typically < 250 mA), switching ground for the GP relay.

But that introduces another potential failure point. Still, for the cost of the controller, it's cheap protection.
 

Bighorn

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So rather than find the actual problem in the system you would rather redesign it.
You'll still have the underlying problem.
Probably a bad ground somewhere and easy to fix.
Go ahead and throw random parts at it though.


Have fun.
 

antennaclimber

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I don't recall what the current is for the GP relay closure is. I agree with not adding a relay to control a relay, more failure points.

I do remember that during the initial GPD design we beefed up the transistor that closes the relay. Seems that the original ones were on the lower end of the ratings for the current demands of the relay. So we use a heavier one able to easily handle the relay.

As for the failures, over voltage, reverse voltage and using a set of metal needle nose pliers to remove the card seem to be the most common issues.
 

MarcusOReallyus

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I don't recall what the current is for the GP relay closure is. I agree with not adding a relay to control a relay, more failure points.
Yeah, then we'd need a relay to protect the relay, and a relay to protect the relay that protects the relay... :roll:



I do remember that during the initial GPD design we beefed up the transistor that closes the relay. Seems that the original ones were on the lower end of the ratings for the current demands of the relay.
Well, well, well. Under-spec'd parts. Why, I am just shocked! Shocked, I tell you! :mrgreen:


As for the failures, over voltage, reverse voltage and using a set of metal needle nose pliers to remove the card seem to be the most common issues.
Well, we did have a strong potential for a bit of reverse voltage a while back when my son reconnected the alts after rebuilding. A few sparks flew, and I had to rebuild them again, but things were working fine after that.

This is a trace problem, though and it looks like a repair to a previous problem. Not done very well, either. It was probably a ticking time bomb, and was only a matter of time. The relay is an ST-85 from NAPA, only a few years old, and hasn't had many cycles. The ground is good.

I think I'll get a resistance measurement and calc and measure the current just to see if there are any red flags. If not, I'll chalk it up to a failure waiting to happen and just order one of your cards.

:beer:
 

AECS

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I am having card issues to. All wires test as they should, wait light works as it should, but blue wire never gets ground. Gonna pull Z4 and test it, otherwise I will be buying a card as well....
 
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