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?