You just have to access the relevant terminals first, Mike, alternator and lamp - to assess in-between faults. The wiring and harnesses are usually well wrapped and not suitable for inspection unless problems are identified as being within the harness…
The lamp is connected to the alt; with ign ‘on’ lamp is powered from ign key and grounded through the alt. With the alt running, there should be +12V on both sides of the lamp - no light then…
The voltmeter problem is not related to the ign warning light if the alt delivers voltage to battery…
Is there some detail view or photo of the alternator connections? I think I’ve found the wire, but am not sure. It’s all filthy and cramped down there. Is it a single connector flat spade terminal? The alt has a napa sticker on it, so it’s been changed. I’ve only been able to feel around the back of it. There’s a male spade terminal and the wire/connector fits rather loosely on it.
It’s a bit awkward, Mike; Jaguar used a variety of alts, some with different connections - not to mention POs.
The ‘all’ used brown/black for the warning lamp…so…? The grime observed may cause the wire to ground - so clean up may ‘do something’? No loose wires in the area…?
There may be an internal fault in the alt, unduly grounding the wire - but it would be somewhat unusual. You may ultimately have to remove the alt to see what is what - which is also unusual…
̶W̶h̶a̶t̶’̶s̶ ̶t̶h̶e̶ ̶r̶̶̶i̶̶̶g̶̶̶h̶̶̶t̶̶̶ ̶ ̶ ̶e̶a̶s̶i̶e̶s̶t̶ ̶w̶a̶y̶ ̶t̶o̶ ̶g̶e̶t̶ ̶t̶o̶ ̶t̶h̶e̶ ̶b̶a̶c̶k̶ ̶o̶f̶ ̶t̶h̶e̶ ̶v̶o̶l̶t̶m̶e̶t̶e̶r̶ ̶t̶o̶ ̶a̶d̶j̶u̶s̶t̶ ̶i̶t̶?̶ Edit: disregard. I just discovered the tach pops out with a twist. Genius!
Regarding the brown/black wire: When disconnected, I get no charging. When connected, I get charging (13.3+) and the battery warning light. I’ve cleaned up things and replaced the connector, inspected wiring, etc. I’ll live with this for now.
t[quote=“Mike_B, post:24, topic:443725, full:true”]
…Regarding the brown/black wire: When disconnected, I get no charging. When connected, I get charging (13.3+) and the battery warning light.
[/quote]
Some alternators require an ‘exciter’ to start charging, Mike. Usually from the brown/black, powered from ign key ‘on’ through the lamp. ‘Most’ alts are ‘self-exciting’ due to remanent magnetism.
While alt stationary; the brown/black wire is grounded through the alt - lamp lit. As the alt runs; it delivers 12V to brown/black, and counters the 12V from the ign key - lamp goes out.
In your case; the brown/black remains grounded/gets no voltage from the charging alt. Either because the brown/black is connected to the wrong terminal on the alt - or there is a subtle fault in the alt. There may also be a fault/short at the lamp; disconnect brown/black from alt - with ign ‘on’ the lamp should be unlit…
Aristides’ schematics, OEM alt, may not be correct for your alternator. You may look for a different connector on the alt for the brown/black? Unusually, there may also be a separate exciter wire involved - what alt do you have?
Routinely, you may check for an external electric leak; disconnect a battery clamp and measure current between battery post and clamp - it should be in the mA range. Failed diodes is indicated by a high current leak in this test. Which will interfere with alt charging capacity; the 13,3V chargin is a bit suspicious - though it ‘should’ not cause warning lamp anomalies…
Failed diodes normally makes the charge lamp glow dimly, a lamp on solidly is either a wiring fault (shorted to Gnd), or the regulator is U/s on the lamp circuit, as the alternator voltage appears to be correct.
Brightly. If I disconnect the brown/black from aternator, the warning light turns off and alternator output drops.
I’ve attached photos of alternator, with some notes added. Perhaps that capacitor/noise suppressor is plugged where the brown/black needs to go? Also I don’t think the thermal limiter should be connected to alternator ground?
As Aristides says, Mike; somehow you should check the relevant connections for ‘your’ alternator it’s most likely a misconnection…
The car wiring may not be compatible with the alternator fitted; it’s based on the OEM alt fitted to the at the time. A PO installing a different alt may have done something ‘non-standard’. And alternator wires should not be directly connected to ground unless so prescribed by proper wiring diagrams - the alt’s body is already grounded and would normally be used internally for required grounds…
Without checking a wiring diagram, the A/c is using the alternator as an engine running signal, so it can only be operated when the engine is running and generating electrical power.
In modern cars yes indeed.
On the 86 XJ not, not at least on mine, unless someone modified it.
And if so, are the Ronco Thermostat and the AC relay bypassed?
Indeed, it looks like some careless / clueless repairs were done in that area… I disconnected the incorrect wire. It didn’t affect the charging light issue. According to napa website this is the correct alternator. I could not find a wiring diagram. It may come down to just changing the alternator, even thought it is charging adequately, even under load. I may consider moving the alt to the air pump location at that time.
