Glow Plug Relay

[stonedel]

My truck has been hard to start in the cold so I thought I would check the glow plug relay. Turned the key on to light up the glow plugs so I could check for voltage.I here the relay click and get 12 volts on batt side and no voltage on glow plug side. So I think bad relay. Install new relay and same result no voltage on glow plug side. Removed glow plug wires from relay and test again. This time after click there is voltage on both post , touch glow plug wires to post volt meter drops to 0 voltage. Both relays test good old one and new one. What might be up with my glow plugs?

[kaya@bernhausen]

try disconnecting one valve cover gasket connector and test again. isolate which side is causing the problem. then, pull the valvecover of that side and see what's going on in there

[NoRalPh]

Originally Posted by stonedel

My truck has been hard to start in the cold so I thought I would check the glow plug relay. Turned the key on to light up the glow plugs so I could check for voltage.I here the relay click and get 12 volts on batt side and no voltage on glow plug side. So I think bad relay. Install new relay and same result no voltage on glow plug side. Removed glow plug wires from relay and test again. This time after click there is voltage on both post , touch glow plug wires to post volt meter drops to 0 voltage. Both relays test good old one and new one. What might be up with my glow plugs?

This manes No Sense to me.... I don't see how it could possibly be the GPs. They are, basically, already a dead short. What more could they do than that to the relay???

Are you sure your testing method is right? Let's go to the basics...

Take the two sm wires off the relay. Get two jumper wires (you've got those sm ones w/alligator clips on them?) and put battey voltage (+) into one of the sm terms on the relay, clip the other jumper on the other term, and touch Ground (-).

The relay should Throw (loud click). At this point you have connected the 2 large terminals on the relay. Battery voltage (+) will be at both sides. Since that relay will supply 200A across those terminals, if the problem was on the other side (GP delivery), anything over that would just SMOKE.

If the GP side drops to "0" then the supply side would have to also (meaning your batteries just dropped to 0). Are you sure that's not what's happening?

[kaya@bernhausen]

hmm. i was thinking too much resistance to allow current to flow. like maybe burnt uvch pins. that still wouldn't seem to make sense though, since op is not testing in series. op, how exactly are you testing? where are your leads?

[lanierboatsales]

What you have is a problem with the supply current to the solenoid. Somewhere between the battery and the solenoid, there is a bad connection or wire. Do the same test with the wires to the glow plugs disconnected while checking the voltage at the fuses for the glow plugs in the fuse box. If you get 12v with no load and 0 volts with a load, then you may have a corroded fuse that wont let the current pass. If the fuses are good and clean, you will need to follow the wires that supply the power to the fuses back to where they tie into the battery. I am not sure but I think they draw power from a junction on the passenger side fender. Someone else may be able to help answer with the location.