QuestionMy 1994 LHS has a vexing problem. The other day, about the same time that my wife turned on the heat--or immediately thereafter, all gauges in the instrument panel stopped working. This included an analog display speedometer and tachometer.
At the same time, she could not change the temperature controls, not the temperature of the airflow, not the volume or the location of air. After a while, the dash started working again and she was able to turn the heat on again. Then after a while, the dash stopped working again and the heat went back to the "stuck" position. In the stuck position, the heat was on full blast and seemed to be mainly coming through the defrost vents.
Any ideas? We have checked fuses and relays and all seem good.
AnswerHappy New Year, John!
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Roland
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Hi John,
There are two possible causes: first would be a power supply issue. Check fuse #17 (5 amp) for the possibility that it has a crack in the wire that is opening and closing on its own as it heats and cools. That fuse supplies power to the body control module and to the instrument cluster. The proper functioning of the heater/ac depends on the operation of the body computer as does the instrument cluster via the digital data communication 'bus' which carries the info to operate the gauges and modify the operation of the ventilation system. So the second possibility is that there is an intermittent breakdown of the bias voltage (5V) on that bus.
So check the fuse #17 and maybe just replace it and see if the system works reliably. If not, then see if the system has stored any fault codes by turning the ignition key "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the check engine light, which remains 'on', to see it begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat the process and counting to be sure of a consistent set of flash counts. Then group the counts in pairs in the order of appearance to form the 2-digit fault codes. The last code is always 55 which means 'end of readout'. Let me know th numbers of the other codes and we can go from there. You can also go to www.allpar.com/fix/codes.html for a list of the meanings of the code numbers.
Roland
