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Jim DeClerck Member 
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There seems to be a key red/white (r/w) wire missing. The wiring diagram shows a red wire bringing power to the panel light dimmer and 2 r/w wires also connected there. I can find only one of the r/w wires. It has a proper female terminal. This wire powers the light for the heater controls, which illuminates when the headlight switch is activated. The missing r/w wire apparently is supposed to be routed to the junction containing the r/w wires which lead to all the instrument lights but I'm unable to locate it after removing the instrument panel and searching for it. Any ideas? Maybe I'll just have to cut open the junction wrapping and add a new wire to replace the missing r/w wire. |
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Mark Rosenbaum Member 
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One of the red-white wires runs from the dimmer to the clock lamp and thence to the heater controls lamp. The second red-white wire runs from the dimmer to Pin 3 of one of the two instrument pod wiring connectors. The junction you mention is located in the instrument pod wiring harness. If necessary, new connectors and properly color-coded wire are available from British Wiring ( http://www.britishwiring.com ). |
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John Kimbrough Member
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Jim, you might want to check out my wiring diagrams on the following: http://home.comcast.net/~jrkengr2/ |
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Jim DeClerck Member
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John, Thanks for reminding me about your excellent site. I just looked at the photo of the switches for the lights, dimmer and hazard warning. It is very clear that there are 2 RW wires connected to one of the dimmer switch terminals and 1 R wire connected to the other terminal. And that's my problem. In my car, 19336, there is only one RW wire connected to the dimmer in addition to the R wire connected to the other side. The one RW that is connected powers the clock and heater control lamp, as noted by Mark. Close inspection of the RW wire junction connecting to the 6 instruments reveals that there are 7 wires gathered there. So the missing RW wire from the dimmer switch is apparently somewhere in the under-dashboard bundle of wires and hidden by the wrapping. I guess my next step will be to cut the wire bundle wrapping, try to trace the 7th RW wire back to its origin and then splice on a length of wire to connect back to the dimmer. |
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Jim DeClerck Member
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Further re: 19336: I have removed the black rubber covering which insulates the solder junction of the 8 RW wires serving the instrument lights. Then I clipped one end of a jumper wire onto the solder junction and the other end onto the + terminal of the battery. One light went on, the external auxiliary oil pressure light, which I can't find in the wiring diagram, and which is embedded in the shroud over the oil pressure gauge. The other instrument lights did not illuminate. During this test the headlight switch was off since I assumed it was not needed if I supplied 12v directly from the battery. The mystery continues... Last edited on 01-27-2007 11:19 pm by Jim DeClerck |
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Mark Rosenbaum Member
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Your test should have caused all the instrument pod bulbs to illuminate. Since only the oil gauge light did, then either all the other bulbs are bad, or there are multiple defects in the instrument pod wiring harness, or a PO did something inappropriate. The oil gauge light is shown on the wiring diagram for US cars as the hazard warning switch light, and owes its existence to a federal mandate requiring such a light. IIRC this light connects to the pod harness via a pair of bullet connectors. If a problem exists with the grounds in the pod harness, a PO might have hooked the oil gauge light's ground wire to the ground-side bullet connector for the clock, as a stopgap measure, and never got around to actually fixing the problem. IIRC the various instruments (and their light bulbs) are connected to the pod harness ground junction through wires that attach to their cases. Rusty cases will disable these connections. The pod harness ground junction is wired to pin 4 of one of the pod connectors and thence to the lefthand ground junction in the main underdash wiring harness. |
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Jim DeClerck Member
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Mark, Thanks for clearing up the external oil gauge light question. You are a deep and valuable reservoir of Healey knowledge. The wiring diagram glued into the back my old Owner's Manual has a marginal note saying the Hazard Warning Switch Light is installed on W. German cars only. But does not give any explanation for its use or location on cars destined to other markets. I thought there might be a ground fault but my continuity tests for the grounding were successful. And individual bulbs tested outside their sockets do illuminate, so it's not the bulbs. And there is continuity from the RW wire solder junction to the inside contact of the bulb sockets!!! This defies logic. Now I'm really intrigued and have to solve this problem..... |
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