HVAC unit has several lights that do not work.
- Thread starter SKastler
- Start date
What year? My take on it there is a wiring fault going to the unit.
Briefly looking at the'96 service manual, there are two power inputs for illumination, one being the variable dimming input for instrument illumination.
Do you know if it could be the dimming input? If we could narrow it down and identify the model year, we could likely find the problem.
Briefly looking at the'96 service manual, there are two power inputs for illumination, one being the variable dimming input for instrument illumination.
Do you know if it could be the dimming input? If we could narrow it down and identify the model year, we could likely find the problem.
Can you use the instrument panel dimmer switch next to the headlamp switch (with the lights on) and adjust the instrument panel lighting?
I've never ran across this problem before, so I'm not 100% certain what exactly dims and what doesn't dim specifically on the EATC control panel.
I'm pretty sure the LED screen dims with the instrument panel lamps but I'd be curious if the buttons do. Something that may help us diagnose the problem while I find time to look at my '93 in the garage along and find the Electrical/Vacuum Troubleshooting Manual.
Meanwhile, maybe someone else might chime in.
I've never ran across this problem before, so I'm not 100% certain what exactly dims and what doesn't dim specifically on the EATC control panel.
I'm pretty sure the LED screen dims with the instrument panel lamps but I'd be curious if the buttons do. Something that may help us diagnose the problem while I find time to look at my '93 in the garage along and find the Electrical/Vacuum Troubleshooting Manual.
Meanwhile, maybe someone else might chime in.
Here's what I know...
Testing the EATC panel lighting on my '93... with the lights OFF, only the LED screen is illuminated. With the lights ON, all buttons are illuminated and everything dims with the dimming control next to the headlamp switch.
According to the manual, there are two illumination feeds to the EATC module. One is general illumination and the other is the dimming input. My guess is the general illumination feed is used to light up the LED screen when the instrument lamps are off and the dimming input from the auto lamp pulse width dimmer switch output is used to all bulbs when the instrument lamps are on.
Here is some pics from the manual...
You can see from the wiring diagrams and the connector pinout the two circuits in question.
Circuit 88 (BK/W) should have a variable voltage (0-100% battery voltage) depending upon the rotary dimming switch next to the headlamp switch.
Testing the EATC panel lighting on my '93... with the lights OFF, only the LED screen is illuminated. With the lights ON, all buttons are illuminated and everything dims with the dimming control next to the headlamp switch.
According to the manual, there are two illumination feeds to the EATC module. One is general illumination and the other is the dimming input. My guess is the general illumination feed is used to light up the LED screen when the instrument lamps are off and the dimming input from the auto lamp pulse width dimmer switch output is used to all bulbs when the instrument lamps are on.
Here is some pics from the manual...
You can see from the wiring diagrams and the connector pinout the two circuits in question.
- Circuit 235 (R/BK) - Illumination - Pin 4 on Gray Connector C273
- Circuit 88 (BK/W) - Dimming Input - Pin 18 on Gray Connector C273
Circuit 88 (BK/W) should have a variable voltage (0-100% battery voltage) depending upon the rotary dimming switch next to the headlamp switch.
I can't explain your issue but I would start by checking the proper voltage at the connector for both the circuits I described.
If both circuits prove out, then it must be internal to the EATC module, and yes both could be faulty. We are talking about 25-30 year old parts that have the same strengths and weaknesses. Case in point is the prevalence of faulty air bag diagnostic modules which has seemed to have increased with time.
I searched for internal wiring/control schematics for the modules but did not find anything.
If both circuits prove out, then it must be internal to the EATC module, and yes both could be faulty. We are talking about 25-30 year old parts that have the same strengths and weaknesses. Case in point is the prevalence of faulty air bag diagnostic modules which has seemed to have increased with time.
I searched for internal wiring/control schematics for the modules but did not find anything.