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Old June 26th, 2019, 21:52
8Mud's Avatar
8Mud 8Mud is offline
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Re: Erratic turn signal flasher relay

I'd ohm test the ground part of the bulb sockets to a known good ground. The only way to know a good known ground is an ohm test to battery neutral.
Check the voltage at the bulb center contact to a known good ground.

There may be resistance in the power side lowering the voltage/amperage below tolerable levels.

Even with good voltage to the bulb socket, there can be excessive resistance.

The way the nonelectronic modules work is a bimetal, they are thermal flashers. Old technology, a copper/steel piece of metal heats up breaks contact. cools makes contact again and repeat. The module is roughly tuned to the watt (volts X amps = watts) usage/flow. The bimetal does fatigue and wears out on occasion. But the most common problems are a mismatch of the flasher and the watt usage/flow, either because of the grounds, voltage/amp supply or bulb mismatch (either the number of bulbs, burnt out bulb or the bulb watt rating).

You really have to ohm test the ground circuits, many places for this system to go wrong.

If you don't already have one, add a ground from the battery negative to the inside fender well, this is a partial workaround for some of the ground troublespots. Can't really hurt anything, but may help.

I've actually had the best luck with a universal flasher designed for trailer usage (6 bulb). I don't know exactly why but they seem to work.

Just a couple of WAGS (wild assed guesses) have you done any dash work lately, is the ground to the lower left dash knee panel mount connected (forgotten ?). Turn signal contacts under the steering wheel crispy? The front clip lighting harness connector behind the airbox severely corroded? If you have a stick shift and clutch, is the clutch cylinder leaking brake fluid onto the fuse block? Check the wiring near the headlight buckets for cutting or rub-throughs. Double check the splices, you mentioned some running light turn signal mods.

I've had some serious issues troubleshooting the lighting on XJ's, time intensive and many not so obvious problems can crop up.
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Old June 28th, 2019, 15:04
br1anstorm br1anstorm is offline
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Re: Erratic turn signal flasher relay

Thanks 8Mud for that detailed advice. I'll dig out a meter and do what I can to test ground connections and voltages in the way you suggest.

Just to respond on the other points....

I don't at present have an extra ground connection (or as we call it, an "earth strap") from battery negative to chassis. I did fit one such strap on another car I have, for much the same reason, so I may try it.

I haven't done any dash work. I confess I don't know exactly where "....the ground connection to lower left dash knee panel mount..." might be, but certainly haven't removed or disconnected anything that might fit such a description! Might need a pic or diagram to identify it.

Turn signal contacts and switch on steering column seem OK. Wiring and connections around the headlights and airbox also seem OK but I can't say 100%. My XJ is auto, so no stick shift or clutch to leak fluid.

The mod to the lighting wiring was to have the original sidelights converted to orange turn-indicators. The sidelight wiring now feeds a small bulb within the replacement headlight units - which are replacements because although it's an LHD vehicle I have to have left-dipping headlamps to be legal in UK. Fortunately Hella makes headlamps which have both the main/dip headlight bulbs and the sidelight bulbs within the same unit....

Anyway, I'll check the splices as best I can (don't want to undo all the carefully-reconfigured knitting and risk creating more problems).

The only other possible clue - which might be totally irrelevant, but might equally be a key piece of evidence - relates to the point about dash work. My speedometer needle behaves erratically too. This pre-dates the turn/hazard modules misbehaviour by about a year. The odometer works fine and clocks up the mileage accurately. But the speedo needle has a mind of its own: sometimes takes 15 minutes/several miles to wake up, sometimes rotates anticlockwise, sometimes reads a consistent 20mph more than the actual speed, sometimes works perfectly. I wonder - is this another symptom of a bad electrical or ground connection somewhere behind the dash?
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Old July 12th, 2019, 03:35
br1anstorm br1anstorm is offline
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Re: Erratic turn signal flasher relay

I'm still having problems troubleshooting this (not least because I'm no expert at using ohmmeter/voltage-meter).

The bulb-sockets all seem fine - I think. I have tried to test the hazard flasher unit socket in the fusebox. I assumed one terminal-socket would be live when the hazard switch was on, and the other was a ground. But the live one only has power when the ignition is on (though the hazards should surely function even with ignition off?).

I'm wondering whether there is a bad ground somewhere. But exactly where and how do I check them? I cannot see how to get behind the fusebox in the footwell to check the contacts there.

I have the workshop manual wiring diagram, which lists no less than 11 ground-connections to the chassis. But it doesn't show exactly where these grounds are located on the vehicle.

I can see most of the ones in the engine bay. But ... where exactly are the grounds on the "left side shield" and "left side cowl", "left side cover" and "right side kick panel"? Crucially, which ground(s) serve the lighting and turn indicator circuits? Can anyone point me in the direction of a diagram or set of photos which actually shows where to find the various ground-to-chassis contacts?
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Old July 18th, 2019, 14:19
br1anstorm br1anstorm is offline
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Re: Erratic turn signal flasher relay

Well, time for an update, and it seems the problem is (almost) solved.

Long story short, it turns out that it was the blue plastic Wagner 224 that was faulty. With all the swapping over of the two flasher units (blue Wagner 224 and silver Wagner 552) to see what worked and what didn't, I was - for a while - confused as to which socket in the fuse panel was for the turn-circuit and which for the hazards.

Anyhow, I now have good flasher-units in both sockets, and the turn indicators and hazards work as they should.

Meanwhile with the help of advice from cruiser54 I checked and cleaned up most of the ground connections (which were actually not corroded). The one that is hard to reach is below the steering wheel, under the dash, so that remains to be checked.....

The faulty speedo needle seems to be an unrelated problem: I think the speedo on my '93 XJ is electronic, not driven by a mechanical cable, but I have no clue how to make it work normally..
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Old July 19th, 2019, 10:37
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Rob Mayercik Rob Mayercik is offline
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Re: Erratic turn signal flasher relay

Glad to hear you got the blinkers working right.

As to the speedo, it should be electronic - the thing on the tcase that has the little gear on my '92 just has an electrical connection on it, so odds are yours should be the same. The fact that the odometer is working properly leads me to believe you're getting a good signal from that and it's getting to the cluster OK.

I don't know the innards of the cluster/speedo, so I'm not sure if the cluster circuit board is providing two copies of the signal into the speedo/odo unit (one for odo, one for needle) or just one and it's being split internally, but if you have access to the factory wiring schematics for your truck it might show something. I can try to remember to check in the factory service manual for my '92 over the weekend, as far as I know 91-95 models used the same cluster so it may be applicable.
1992 Cherokee Laredo: "A wonderful balance of grace and rust"
1984 Dodge Omni
2002 Volkswagen Jetta GLS TDI
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