New GP relay help - s603

[86 K5 Blaz]

Before I begin, yes I have searched and yes I have done all the basic troubleshooting. All I have found is people switching to manual glow plugs. I want to fix mine properly.

Here is what I have: my stock glow plug relay died, I looked around and found my local oreily had the s603 in stock. I bought that, put it on with the red wire on the small post nearest the 12v input. The blue wire on the other small post and the plug plug wires and the sensor wire on the large output side. When I turn the key I get the wait light for a few seconds. But no relay click, and no load on the battery. I tried switching the small wires with no luck.

When I remove the controller wires and test the relay manually, it works fine.

My fuse is fine, all the connections are fine, my glow plugs are new. It is converted to 12v with the resistor bank removed.

It is to my understanding that the red wire switches the ground on and off for the relay, but mine is putting out a positive 12v. My GP card worked fine before my relay died and still looks to be new. No burnt spots or blown components.

What's next? Is there anything else I can try or test?
Thanks in advance.

 

[mistaken1]

The light blue wire is the ground.

Did you download the manual and follow the troubleshooting procedure in there to test the card?

If you can manually ground the relay terminal with the light blue wire and the relay closes go to the card and try to ground the light blue wire there. Does the relay still work? Yes, check the card. No check the wiring from the relay to the card.

Did you check and clean the grounds under the drivers side dash (way up high on the side)?

 

[86 K5 Blaz]

I just followed the TM for testing the controller card, all the wires check out fine. If I manually ground the blue wire at the relay or at the card, it will turn the relay on. I only seem to have 2 wires on the "ground" area, but they are both fine.

This is looking like its the card. Is it possible that my relay dieing killed it?

 

[M1008driver]

When I turn the key I get the wait light for a few seconds. But no relay click, and no load on the battery. I tried switching the small wires with no luck.

With the gp resistor bypass I no longer get a click when my wait light is on, nothing, no click chatter or anything. I do get a short buzz when my voltmeter moves from yellow to green shortly after I start my M1008.

I have done the doghead mod and gp resistor bypass too removing the resistor from my truck. My gp card is new from CUCV Electric and seemed to help slightly after the mods.

Does your truck start and run? If so I wouldn't be alarmed.

 

[86 K5 Blaz]

When I manually jump the relay, I get a solid clunk and it starts fine. Without that, it will crank all day without firing. I have a hard time justifying the card being bad. It looks to be in great condition and nothing burnt. I ohmed all the circuits on the board and none of the circuits are broken.

 

[M1008driver]

I went out and started my M1008. Before starting the voltmeter is in the yellow and does not move until the truck starts. Just turning the key does not move the voltmeter either. After cranking the engine the indicator needle drops slightly and then moves to green after several seconds.

I don't think your card just went bad. There is a wire in the wrong place, bad connection, or maybe a bad gp relay solenoid (S603). If you disconnected your batteries while working check the grounds. Probably not the problem, but...

EDIT- TM 9-2320-28$20
Table 2-4. Electrical Troubleshooting
Page 2-64 & 2-65 Change 2

19. ENGINE CRANKS BUT WILL NOT START; ENGINE COLD; “WAIT” LIGHT OPERATES

Step 1. Ensure that key is in “OFF” position. Check for voltage between glow plug relay terminal where orange lead connects and ground.

If there IS voltage, replace glow plug relay (see paragraph 4- and perform
step 3.

If there is no voltage, perform step 3.

Check the TM for more information

 

[86 K5 Blaz]

Ive followed the TM and it points to the card. The relay does not come on by itself. If I jump the light blue wire to a ground it clunks, drops the volt meter down as it should, and fires up immediately after I turn the key.

 

[doghead]

Did you test your temp sensor? If it is bad or disconnected, your card will not function properly.

 

[86 K5 Blaz]

Thanks for everyone's help so far, and sorry for the late response. The temp sensor wires checked out fine according to the TM. I figured out today that both of the small wires going to the relay are grounded when the key is off then both are +12V when the key is on. Why isn't the blue wire staying a ground?

 

[doghead]

The controller switches the light blue wire(ground), to activate the relay. (not the positive side)

Both small terminals are connected by a long winding of wire(a coil). So, with the key is on, then you would see voltage on both small terminals(if the controller is not activating). If the controller is activating the relay, the light blue wire would be grounded.

This is all listed in the -20 TM GP troubleshooting section.

Is your relay a isolated ground relay? It MUST be, to work correctly in the CUCV.

To test for isolated ground, check for continuity between either of the small terminals, to the shiny mounting frame of the relay(where the bolts mount it to the fire wall). If there is any continuity, then it is the WRONG relay and may cause a controller card to burn out as well as your glow plugs.

 

[86 K5 Blaz]

I've read the TMs and followed them through. I cannot really come to any conclusion though. The relay is indeed and isolated ground relay. I feel like the card isn't sending a ground out through the blue wire. If I ground that out from the GO controller box then it will kick on.

The temp sensor seems fine, relay is new and isolated, wait light comes on properly according to temperature, the small red wire switches on properly, but no ground on the blue wire.

The only thing left that I can think of is the card. But it looks brand new.

 

[doghead]

You can try cleaning the card contacts with a pencil eraser.

As the TM says, you test everything, then replace the controller if it still does not work.

 

[Skinny]

I've read the TMs and followed them through. I cannot really come to any conclusion though. The relay is indeed and isolated ground relay. I feel like the card isn't sending a ground out through the blue wire. If I ground that out from the GO controller box then it will kick on.

The temp sensor seems fine, relay is new and isolated, wait light comes on properly according to temperature, the small red wire switches on properly, but no ground on the blue wire.

The only thing left that I can think of is the card. But it looks brand new.

I think you answered your own question. If you ground out the blue wire at the card and the rest of the GP system works, then it all falls on the card. If the card is cycling incorrectly it may be a temp sensor or failed GP's but it will still work somewhat. Pony up the $70 and get a new one from CUCV Electric.

 

[mr.travo]

Any updates on this??? Mine does the same, but I found that cycling the key 3 or 4 times, everything will finally work and I can see the load being pulled (glow plugs finally cycling).