Stop Solenoid Electical Problem

Hi, new to the forum, but stumped by an electical problem.

I have a 2.5TD 90.

The stop solenoid gave up the ghost. I managed to remove the plunger and get home.

I have subsequently replaced the stop solenoid and now have a peculiar electrical problem.

When the ignition is switched on the new solenoid clicks away fine and the engine starts and runs no problem.

When the ignition is switched to the off position, the voltage at the stop solenoid should drop to zero, however I am getting 2 volts which is just enouph to keep the solenoid energised (an thus not stopping the engine).

Another stage anomology which has appeared at the same time (so I assume is linked) - when I start the engine (but dont rev it) the battery "charge" light stays lit. With the charge light on, when I switch the ignition off the stop solenoid works perfectly.

If I blip the throttle, the charge light goes out, but the backfeed to the solenoid appears when the ignition gets switched off.

When I investigated further, switching ignition off, the 2 volt backfeed appears to be comming from the alternator as when I pull the multiplug off the back of the alternator, the backfeed stops and the engine stops.
Having checked the wiring diagram in the hayes manual it looks like the the ignition switched feed to the stop solenoid is "linked" to the charge light via the "ingition light resistor".

Where is this resistor located ?

Have I damaged the alternator ?

Is the charge light being on at inital start up and going off after reving normal ?
Is this a common problem ?

What fault finding can I do ?

Can anyone explain how the charge/ indication lamp actually works, I cant figure it our, I cant see how you get a potential to make the lamp light as it appears to have +12v to both sides ?

Thanks for any advice.
regards
Douglas

you could bypass the ign and wire the solenoid via switch straight to + then see what happens

i think i would just change alternator there cheap

try checking the resistor and diode this was fitted to stop solenoid being held on by ignition light circuit

Hi all,

I hace checked the alternator. 12.8v at the battery with engine off, 14.3v at the battery with engine on at fast idle. So i dont think its a problem with the alternator.

I have tried a direct feed from the battery positive to the stop solenoid. Everything works as expected; when you remove the direct feed, the "plunger" drops and the engine stops.

This suggests the backfeed from the "charge light" is the problem. I am going away to take the dash to pices to try and find this resitor and diode.

How can I check the operation of the diode ? (excuse my ingorance)

If its faulty, can it be replaced easily ?

Regards
Douglas

Still investigating the problem, a couple of new questions which hopefully someone can answer:-

The small wire connected to my alternator (brown / yellow); what direction of travel is the "current" in this wire. I think it is the ignition feed to the "voltage regulator" section of the alternator, but stand to be corrected?

I have found the charge light resistor, buried away behind the dash, it is the same size as a glass type fuse though has a corrugated / braded centre section. Mine looks a bit tatty, I checked the resistance and its about 100 ohms, does anybody know what it should be. If its goosed, where can I get a new one, I cant see it listed in of the catalogues.

Should a 1987 2.5TD with a 19J engine have a diode in the charge light circuit ? The wiring diagrams suggest not, however I have a vague recloection of seeing one when I put the new bulkhead on. I dont want to go stripping the dash down to remove the "parcel shelf" only to find out I imagined it ?

Regards
Douglas.

current is fed through wire to alt and light glows when alt running same voltage is produced putting light out ,still think you need to look at alt

the diode is to stop feedback through the ignition warning(charge Light) light via the brown yellow from alternator if you have located the diode if it was ever fitted or you can fit a IN4007 diode yourself the diode should only pass from alternator to light ,most modern test meter's have diode test if not a 12 volt lamp in-circuit should confirm diode

Update - Problem Solved. Just in case anyone else experiences a similar problem.

I replaced the alternator (A127), no change, the supurious voltage was still there.

I pulled the dash apart and located the resistor, which was housed in the old fashioned "push and turn" fuse holder directly behind the speedo pod. Resistor appeared ok and had a 100 ohm reading.

Checked the whole wiring loom but no diode. From checking the wiring diagrams this appears to be correct for a 19J engine.

Whilst discussing the problem with a electical engineer, a very basic question was raised !! - Is the spurious voltage a new fault or has it always been there (i.e. not actually a fault).

That set me thinking !! Maybe I dont actually have a problem with the charge circuit.

As I could not go back in time to when the old stop solenoid was working and check the ingition of voltage I decided to try replacing the new solenoid.

I splashed out on a delphi stop solenoid (quality unit) and all is well. It appears that the 2.5 volt backfeed has always been present, however this was just enouph to keep the cheap solenoid energised.

The moral to the story:-

check the facts, establish what has actually changed and dont buy cheap stop solenoids.