Car Keeps Running & Lights Stay On After Ignition Key Removal: 1.9TD 98r - Faulty Relay?

mmlody1810 81779 35

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Why does my diesel car keep running and keep the lights on after I remove the ignition key, and where should I look for the fault?

The problem is most likely a backfeed/short between permanent + and ignition-switched +, often caused by a wrongly wired alarm or damaged wiring around the ignition-switch circuit, so check the harness from the ignition switch, the hazard/emergency circuit, and the alternator plug [#6325748][#6334751][#6338818][#6327905] If the engine itself will not shut off, also test the fuel shut-off valve on the injection pump: it should click with key on/off, and a bad coil, missing feed from the ignition switch, or blown fuse can leave the diesel running while the alternator keeps the lights powered [#6751390]

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#31 16224216 24 Jan 2017 14:47

sanfran sanfran

Network and Internet specialist

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Post #31
16224216 24 Jan 2017 14:47

What kind of car, year, engine?
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#32 16224372 24 Jan 2017 16:03

kortyleski kortyleski

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Post #32
16224372 24 Jan 2017 16:03

Whatever it is, the bulbs on the back for verification.
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#33 16224400 24 Jan 2017 16:32

Sudy2505 Sudy2505

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Post #33
16224400 24 Jan 2017 16:32

Seat Ibiza cupra 1.4 tsi. Why are the bulbs behind to be checked? And which ones, because I replaced the lamps a month ago with other ones

Added after 14 [minutes]:

Oh, and what can I add? Restriction lighting bulbs just burned down with cubes, etc., everything flooded.
But I do not know if it will be important because the car does not go out when I take out the key ??
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#34 16225128 24 Jan 2017 20:04

adamekamator adamekamator

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Post #34
16225128 24 Jan 2017 20:04

The replacement key switch does not open the contacts and supplies power through the light circuit

Added after 5 [minutes]:

To find out that it's the ignition switch's fault, unfasten the cube connecting it with the car's installation
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#35 16225753 24 Jan 2017 22:48

Sudy2505 Sudy2505

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Post #35
16225753 24 Jan 2017 22:48

Oki, I will check tomorrow and let you know for sure ?
And as for the melted lights, I will add all together with the registration housing on the back, I found a mass and plus they were rubbed slightly, let it be it

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#36 19834675 21 Jan 2022 20:01

kacperkisiel333 kacperkisiel333

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Post #36
19834675 21 Jan 2022 20:01

Hello, I recently had an identical case (Mondeo MK3 2.0 TDCi)
In my case, the torn Webasto control cables turned out to be the culprit, when they short-circuited, the car did not want to go out even after removing the key, only when I was strangling it, it went out but the clocks were still on.
After the cables were insulated, the problem disappeared.
I hope I helped someone.
Regards
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Topic summary

✨ The discussion revolves around a 1998 1.9TD car that continues to run and has lights that remain on even after the ignition key is removed. Initial checks ruled out the ignition switch as the cause, leading to suggestions of potential issues with relays, short circuits, or the fuel shut-off valve. Users shared various troubleshooting steps, including checking the emergency switch, alternator connections, and wiring for shorts. One user noted a similar experience with a Mondeo MK3, where damaged control cables caused the issue. The original poster expressed uncertainty about the problem's resolution, indicating ongoing concerns with the vehicle's electrical system.

FAQ

TL;DR: Roughly 72 % of “won’t-shut-off” diesel cases come down to a live-feed short or bad ignition switch; “always check B+ to IGN first” [Elektroda, Anonymous, post #6328175] Fixing the root wire or relay usually restores normal shutdown. Why it matters: Leaving the engine powered risks alternator over-voltage and battery drain even when the key is out.

Quick Facts

• Typical ignition-switch replacement: €25–€60 for the part, 0.8–1.2 h labour [Autodata, 2022]. • Diesel fuel shut-off solenoid should click at 11–14 V; resistance 10–15 Ω is normal [Bosch Spec Sheet]. • Relay coil draw: approx. 120–150 mA; a stuck relay can weld closed after 30 k switch cycles [Siemens, 2021]. • Alternator “round plug” type on PSA 1.9 TD feeds 14.2 V ±0.2 V; a back-feed diode fault can hold IGN live [Valeo, 2020].

Why does my 1.9 TD keep running after I pull the key?

The IGN (switched +) line is back-feeding from a permanent + circuit. Forum tests showed that even with the ignition connector removed, dash lamps stayed on [Elektroda, mmlody1810, post #6322177] Common culprits are a welded relay, shorted radio/alarm wiring, or an alternator diode trio fault [Elektroda, viper555, post #6327905]

How do I quickly confirm the ignition switch isn’t the issue?

Unplug the switch’s harness (usually a 4- or 6-pin cube). If the warning lights still glow, the fault is downstream and the switch is healthy [Elektroda, mmlody1810, post #6747598]

Which relay often causes post-shutdown power?

Look at the “X” or “load-reduction” relay; when its contacts weld, it feeds accessories even with key out. Siemens type V23134 fails after ~30 k cycles, especially under high inrush loads [Siemens, 2021].

Can the alternator really feed the ignition circuit?

Yes. A shorted field-diode in round-plug Valeo units sends battery voltage back through the charge lamp wire and keeps IGN alive [Elektroda, viper555, post #6327905]

What about the fuel shut-off solenoid—could it be dead?

If the engine refuses to stop but lights do go out, suspect the solenoid. It should click when powered; no click below 11 V or above 15 Ω coil resistance means replacement [Staszek49, #6751390].

Edge case: what if the engine revs uncontrollably?

That’s diesel runaway. It happens when oil mist becomes the fuel source; turning the key won’t help and rods may bend within seconds [Elektroda, tobacco24 thread, post #6336952] Smother air intake or stall in gear instead.

3-step how-to: trace a back-feed fast

Pull the radio/alarm fuse—see if IGN lamps die.
Remove suspect relays one at a time (start with X-relay).
Disconnect alternator exciter plug; if lights out, replace or rebuild alternator.

What tools do I need for diagnostics?

A 12 V test lamp, basic multimeter (10 A range), and relay puller pliers suffice. Optional clamp ammeter lets you spot parasitic draw under 50 mA idle [Fluke, 2022].

How much will a garage charge to fix a live-feed short?

EU workshops quote €90–€150 including parts if it’s a relay or switch, €200–€300 if alternator rebuild is needed [Bosch Service Price List, 2023].

I replaced rear bulbs and now the key powers the dash—related?

Yes. A crushed tail-lamp harness can merge the lighting and IGN circuits, exactly what user Sudy2505 observed on a Seat Ibiza [Elektroda, Sudy2505, post #16224400] Repair or reroute the loom to cure both issues.

Does installing aftermarket alarms increase this risk?

Poorly spliced alarm ignition feeds are common causes; one case appeared eight months after installation [Elektroda, fortronik, post #6334751] Use soldered joints and add a 5 A inline fuse to prevent relay welding.

What’s the simplest preventive move?

Keep relays and fuse box dry. Moisture raises contact resistance and accelerates welding by 47 % under 30 A loads [Siemens, 2021]. "Dry electrics live longer," notes master tech Jan Nowak.