I'm pretty sure it's the switch that's bad. Now.

I just got arc from the large wire to ground
while disconnecting known good timer.
(ignition off, key removed)

Would this also fry the timer, and drain the battery
without blowing the 80A fuse?

What's the PITA factor on the ignition switch replacement?

Thanks,
Bri

__________________
'85 300DT 170K
'99 R1100RS 63K
'84 300DT 126K ate her own camshaft
'83 300DT 252K executed by non-driver
'68 F-100 138K sold (why?)

__________________
'85 300DT 170K
'99 R1100RS 63K
'84 300DT 126K ate her own camshaft
'83 300DT 252K executed by non-driver
'68 F-100 138K sold (why?)

The malfunction may still be the timer itself. No the 80 amp fuse is not going to blow if the circuit is always active. Draw remains less than 80 amps. Locate the wire feed from the ignition and disconnect to separate the relay from the ignition switch.

and ignition off,
I got strong sparks from the large wire (with the 10mm nut)
to ground.

My old timer is fried, solder dripping across the circuit board.
Before I removed it, it sounded like a synchronous motor(with gravel)

Battery was draining fast. Sometimes.

I could only start the car with the timer from my other car.
Don't want to blow that one too.

Thanks,
Bri

__________________
'85 300DT 170K
'99 R1100RS 63K
'84 300DT 126K ate her own camshaft
'83 300DT 252K executed by non-driver
'68 F-100 138K sold (why?)

Give me a few minutes to go look under my hood. I suspect that wire you got sparks from is the power feed to the relay contacts. When the relay control closes them the high current goes through the 80 amp fuse to the glow plugs. Will add to this post in a couple of minutes. I personally dislike looking at key switch schematics.

Okay then It was normal to get a spark to ground as the relay contact feed power is present with the key off on the 10mm nut line. Here is your common sense test. Put the test relay back in but leave the smallest plug disconnected. Use a test meter or test light to verify the glow plugs are not getting power. There will be none if that relay was properly operational in your other car.

Next while monitoring the glow plugs for voltage plug in the small plug. With key off there should be nothing and thats exactly what I think you will find. Then turn on key to glow circuit activation and while still monitoring the glow plugs wait for them to go through their cycle and shut down.All should be well. Their is little risk for your substitute relay by observing.

A lot better than getting involved with key switch circuit problems as well. Now if that substitute relay will not turn off after an appropiate time that you can probably guess from experience the key switch circuit does become a suspect.

Electrically by following this proceedure there is in my opinion no risk that I can think of to your substitute replacement relay. The relay contacts in our glow plug relay take a beating with time. Since the relay coil will generate heat if constantly on a mess inside of your old relay is to be expected. Or if the primary control transistor had shorted out it too could have caused lots of generated heat and melted solder. This type of senario I would class as typical on failed glow plug relay type of devices. Let us know how you do.

Thanks Barry,

I'm gonna try that right now.

Bri

__________________
'85 300DT 170K
'99 R1100RS 63K
'84 300DT 126K ate her own camshaft
'83 300DT 252K executed by non-driver
'68 F-100 138K sold (why?)

The large wire is constant power.

__________________

Gone to the dark side

- Jeff

I have been looking at the schmatic of the relay in the manual; built into/inside of the relay is a Resistor that acts as a temperature sensor and there is also a timer. I think either of these 2 parts of the relay could also cause the problem you are haveing.
It could also be the ignition switch!
So it looks as if there is no clear choice unless you can borrow a good relay from some one. It needs to be the exact same ralay as the older ones have a temperature sensor that is not inside of the regulator and somwhere on the engine with its own wire.

__________________
84 300D, 82 Volvo 244Gl Diesel

I made a couple short trips last night,
unplugging the small plug after startup
Keeps the battery from dying.

I ordered a new timer, which I definitely need,
and a new Ign switch for 30 bucks.

meanwhile, I'm gonna drive it to work now.

thanks guys,

Bri

__________________
'85 300DT 170K
'99 R1100RS 63K
'84 300DT 126K ate her own camshaft
'83 300DT 252K executed by non-driver
'68 F-100 138K sold (why?)

Isn't the glow-relay powered by the same contact as the starter?

__________________

Gone to the dark side

- Jeff

If that was the case, the glow plugs would only operate while the starter was engaged.

When the starter is energised it cuts the glow plug relay off. All current is available for the starter function then. Called a starter lockout function actually. This is wrong as it is a glow relay circuit cutout I believe.

As soon as the starter has finished cranking the relay is re energised again for the balance of it's cycle. My schematic is the one in the old haynes manual. Not the best to use. Just better than nothing.

On an '83? I didn't think that the afterglow was available until the '87 190D Turbo.

__________________

Gone to the dark side

- Jeff

My information suggests that the power to the glow plugs (except for an afterglow-type relay) is cut when the key is released from the start position.

You may be right. I tried to follow the glow relays external wiring on my hayes schematic. I Did not complete the task yet. Afterglow was not factory equipment till the nineties I thought unless retrofitted.
I was a little suprised with the requirement for four feeds to control the relay. . Plus the heavy 12v feeder.

Either my eyes have dropped off more than I thought or that hayes manual wiring schematic is a poor faded printing. I guess it's time I spent some money on factory service literature.

If what you say is true than it is more likely to be a bad switch. As you release the key from starting the switch goes back to the same position as was used to activate the glow plug relay initially. So there would have to be some kind of mechanical latching system incorporated in the switch or relay external to the switch to prevent re activation of the glow relay with the switch travelling backwards. That mechanisim or relay if there is probably his problem.

His glow plug relay comes on line again in a random fashion. It manages to close up something again with running vibration if mechanical. I wish I also had a detailed schematic of the insides of the relay itself. The haynes only shows basically a power type transistor and relay with no description of the timing circuit or how those four leads service it.

Last night I was trying to determine exacly how the re activasion was normally prevented by design. Yet without enough information could not tell.

Since his car had the battery going flat etc. Plus his new used test relay was functioning normally in his other car. It is fairly safe to assume his present glow relay is not the problem.

At least the electrical portion of the ignition switch was only thirty dollars he mentioned. That seemingly reasonable price did manage to suprise me.