Glow Plugs not working

[BlueDog]

My old Jetta has a manual glow plug set-up. It uses the relay from the original diesel donor car. I have installed a fuse panel, manual activation button and wiring similar to Vince Waldons pimped glow plug system. This set-up has been working excellent for the past year. Suddenly it's not. So I've been trying to trouble shoot. I found an ampmeter today that reads -200 to +200. I connected it inline on the positive wire going to my fuse block that feeds the glow plugs. When I energize this the ampmeter pegs to the positive direction. I expected there would be an amperage draw of 40 or 50 amps, or less if any G-Ps aren't working, but the needle goes to positive instead. What am I doing wrong?

[Quantum-man]

Your ammeter isn't missing a shunt, is it?

[BlueDog]

I'm electrically illiterate. It's my weakest area of knowledge. I wouldn't know where to even look for answer to this question. I thought the ammeter is just connected inline on the positive wire. On that idea, does it need to be grounded?

[Quantum-man]

I'm electrically illiterate. It's my weakest area of knowledge. I wouldn't know where to even look for answer to this question. I thought the ammeter is just connected inline on the positive wire. On that idea, does it need to be grounded?

I wouldn't think so.
Try ignition again, but disconnect the wire from the glowplug rail. You should get no deflection on your ammeter.
Then connect a light bulb to the glowplug supply wire and earth it. Do you get a slight deflection? Which cuts out after glow period?[The light lighting naturally].
Try jump lead to glowplug rail direct. Run round start car and then disconnect...Reconnect supply wire after tests.

[surfcam]

I used to be in the same boat as you as far as wiring goes. Then I bought the Haynes Basic Automotive Wiring book. Now I'm thinking in the right direction and don't just get a big head ache.

[Fatmobile]

Something that shows 200 amps is going to need to measure the voltage drop across a shunt.
Running 200 amps through the gauge would require huge wires and connections.
Most 60 amp ammeters don't require a shunt and will work with the glow plugs just fine.

[BlueDog]

So I went all through the GP system. Cleaned the connections, soldered the terminals, installed heatshrink tubing, new fuses. Even removed all the GPs and checked them and removed the Injectors and did compression tests. Two cylinders are a little low. I reassembled everything and all works well. Started yesterday in 16 deg. F temp. Thanks for the suggestions all.