Something is draining my battery and also not allowing my 300D to start.

I found my battery dead so I put it on the charger overnight and the battery is charged now.

Hooked up the battery and when I went to the glow position the interior light dimmed. I waited for the glow plug light to go out and then hear a click and no starter turning over the engine. Seems like something is shorted in the glow plug relay. I can pull the plug on the relay to the glow plugs and it does the same thing. Also I have measured all glow plugs and they are fine. The glow plug relay has 12V on the wire with a nut and on both sides of the 80A fuse.

Will a bad glow plug relay not allow the starter to energize?

How can I rule out the key switch?

How can I make certain it is the glow plug relay? I don't have $200 for a new one so will have to try and find a used one if it is bad.

Anyone have any schematics of the glow plug relay. I have the service manual but does not show the entire circuit.

__________________
85 300D Turbo

It sounds more like your battery is bad. If you go straight to start without waiting doses the motor turn over?

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

So I went out this morning and put back in the glow plug relay and hooked everything up and turned on the headlight while watching the voltage on the meter. It went from 12.6V to about 12.3V. Went to glow and it went down to like 11.6V and then stayed there for about 20 secs. after the glow plug light went out. Then I tried to start the car and it started.

I am 99% sure the alternator and battery are working. I am going to clean the connections on the battery good to rule that out but they do not look too bad. I am going to measure the current with everything off and see if it is too high.

I still can't explain why the battery slowly drains and why after I charged the battery last night the car wouldn't start.

__________________
85 300D Turbo

You will get voltage all of the time at the spots in the pic.

You chould charge your Battery up and take the Battery to have it load tested for free.

If it turns out the Glow Plug Relay is at fault you could simply disconnect one terminal of the Battery when you park the Car till you can come up with solution.

__________________
84 300D, 82 Volvo 244Gl Diesel

Is your battery a sealed unit? My Interstate battery was low on electrolyte and would not hold a charge so I filled it with distilled water and every thing is fine. I think that your battery is weak and not holding a charge. As stated, you can have it tested at the local parts store for free. I suggest that you do this first. If the battery is OK, the next step is the voltage regulator, an easy fix if bad.

Basically, if your battery is bad it will discharge itself over a short time.

We find that it is best to look for the simple fixes first and then progress to relays, pumps and what have you.

__________________
"Life is tough...it's even tougher if you're stupid." John Wayne


Dave
Pawleys Island, SC

'79 300CD