Mustang and Ford Performance Forums banner
1 - 4 of 4 Posts

·
Premium Member
Joined
·
1,486 Posts
Discussion Starter · #1 ·
I have decided to reverse engineer the inverter for the electroluminescent backlight in the Termi instument clusters. I have a working inverter that I can use to see what the signals should look like, but I need a couple of dead units to I can take them apart to see how the transformer is wired and to try to figure out what has failed.

Assuming I am successful, I will publish the results here so those who follow will be able to fix their inverters when they fail in the future.

If anyone has a dead inverter they can spare, please PM me so we can make arrangements to get it to me.

Thanks in advance.
 

·
Premium Member
Joined
·
1,486 Posts
Discussion Starter · #2 · (Edited)
My customer's cluster had a bad EL panel it turned out. I swapped his PCB into a junkyard donor cluster to get him back on the road. I have learned that you should measure many MOhms of resistance across a good EL panel. I read about 14KOhms across the bad panel, so low resistance is a symptom of a bad EL panel, not a bad inverter.

It isn't always the inverter that fails. With the good EL panel, my DVM said it was about 43MOhms which then went up to about 100MOhms and then went off the scale.

My customer had assumed that the inverter had failed, so he had bought a SpeedHut inverter, which he included when he shipped the cluster to me. It turned out that the new SpeedHut inverter was also dead so I couldn't see what kind of signal it puts out. SpeedHut has sent a replacement inverter to the customer.

I was corresponding with SpeedHut support about this issue. People have noticed that their clusters are dimmer with the SpeedHut inverter. The SpeedHut support person said that the EL panels brighten and dim based on the amplitude of the sine wave going into the panel. SpeedHut says that the amplitude of the output of their inverters should be 100-200 VAC.

I was able to get a scope on AC signal going into the working cluster EL panel with a working Ford inverter. I saw a 300VAC P-P, 450Hz signal on the scope:

Oscilloscope Font Television Display device Electronic signage



When I unhooked the EL panel to see what the Ford inverter puts out with no load, it shot up to over 400VAC, which is the limit that my scope can see:

Oscilloscope Font Gadget Line Television set



While it is safe to check the resistance of the EL panel with an ohmeter, it is NOT SAFE to work on a powered up inverter. 100VAC can kill you and >400VAC can really kill you. So BE VERY CAREFUL if you decide to test an inverter yourself. Make sure you are not alone working on this stuff and make sure that whoever is with you is CPR trained. I lost a fellow grad student in grad school who was working on a high power laser power supply. We all learned CPR after that. I am not responsible if you get yourself killed working on your instrument cluster.

Also, make sure that your test equipment can handle at least 1000VAC if you are going to test one of these yourself.

Just a reminder, I am still looking for any dead inverters I can get so I can dig deeper into reverse engineering these things.
 

·
Premium Member
Joined
·
1,486 Posts
Discussion Starter · #4 ·
In the SVTP thread that tells how to use a SpeedHut inverter to replace an OEM Ford inverter, people have said that their clusters are dimmer after the replacement.

My customer sent me the replacement SpeedHut inverter yesterday and this one does work. I had also bought an EL panel from a company called GlowHut so I would have a panel I can use for experiments, so I put the stock OEM Ford inverter and the SpeedHut inverter on it so I could compare the results to see if I could explain why the SpeedHut inverter is dimmer. Here are the results:

This photo shows the Ford OEM inverter driving the GlowHut panel:
1659141659020.jpeg



Here is the SpeedHut inverter driving the GlowHut panel:
1659141719073.jpeg



As you can see, the OEM inverter drives the panel to 295V P-P and the SpeedHut inverter drives the panel to 226V, a difference of almost 70V. This explains why clusters with the SpeedHut inverter are dimmer than ones with the OEM Ford inverters.

I then cut off the dimmer pot from the SpeedHut inverter to see how much impact getting infinite resistance on the dimmer pot would get us. That got the SpeedHut voltage up to 228V, just a 2v improvement.

Thought you might find this information interesting.
 
1 - 4 of 4 Posts
Top