Headlight/cluster issue

Hey guys. So my girlfriend’s 91 GT has one headlight that always blows bulbs. Same one every time. Recently, her cluster light went out. We figured out today that if she presses in the headlight switch like 80% of the way, her cluster comes on, but not the headlight.
She also has only one fog light, not sure if the other one blew or just died.

I read that the dimmer switch is a common issue for the cluster, and that the 87-93 GTs have a :poo:ty gauge wire compared to the LXs for the headlights and thats why they blow sometimes. Could anyone shed some light? Would rather not spend $90 for a dimmer switch for it to not be the issue, or buy another bulb for it to blow after a day or two.
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The 5.0’s got the same harness. The GT’s added fog lights to the existing plugs. The fog light wires are undersized and can use a relay system put in.
Incandescent bulbs do not burn out from lower volts or a lack of voltage. Halogen bulbs do burn out from skin oil (often fingerprints) from improper installation or water in the lenses.
I tag team someone for more advice.
The headlight switch or harness connector may be bad. They are known for that. The fog lights overheat the connectors. There's also a wire that runs from the turn signal switch so check that harness connector too. While you're in there make sure the ignition switch electrical connector looks good.

I always wire the fog lights on a gt to come on with a relay for this reason.

The bulb blowing on one side could be because of the headlight housing allowing moisture to get to the bulb. Check those connectors too. I've seen them melt on one pin causing the bug to go out. When you unplug and plug a new bulb in it'll work for a while until the heat from the bad connection corrodes the pin again.

If the dimmer was bad pushing the switch partially on wouldn't change the cluster condition. Sounds like a bad switch or switch wiring.
First check that the fog light bulbs work then go to the link above and do the modification,
Now about those headlights, the multifunction switch turns the headlights on, the connection can get hot and melt, it also supplies power to the dash lights but you have a separate dimmer, its a set of points that ride on a spring. Gets corroded and sometimes even worn out, yeah I know, 30 year old car and somethings worn out, unbelievable. Sometimes you can wheel it back and forth a few times and get it to work but it's temporary.
When dealing with the headlight bulb, if the housing is ok, not yellow and cloudy, don't have moisture inside and the connection is good then I would say someone touched the glass bulb, they don't last long after that. Use a paper towel folded in half.
Now ask your girlfriend to hold your beer, your gonna be busy for a while.
Knowing how to use a test light, or better, a DVO meter will make trouble shooting so much easier.
YouTube tutorials can probably help as much as a lot of typing. Please ask specifics after getting caught up.
This looks like a good starter video.

View: https://youtu.be/RtNMhCzq72M

If you are ok with this, The General can help you from there.

And what makes you think I can help anybody?
I can't even help myself unless it involves cookies or coffee, remember I have a discaimer:
Information give by this member is not to be confused with any real mechanical experience and is to be use at your own risk,
And what makes you think I can help anybody?
I can't even help myself unless it involves cookies or coffee, ...
Save yourself from having to wade through the youtube waters and stick with us, we'll help you light the way. :rlaugh:
You said you could help light the way. Siri is about out of letters here and my Kindle autocorrect is evil.
if @austin3749 knows a some basics, it will help me not have to fire up a Win 10 computer and run a lot of updates.
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