Okay guys, any idea on this one? I have a friend with an '89 Aerostar XLT. Digital Dash. He says when he turns on the headlights, immedialty the dashboard display, everything, cuts out and goes black. Just started doing this, before, when you turn on the lights, it dims slightly, but you can see everything MPH display, guage readouts ect. (I have an '87 Aerostar with digital dash, so I am familier at how they work, when normal)

Headlights remain on, work fine, normal brightness.

Fuse okay.

Anyway, he hasn't done anything yet, but he says his wife in complaining when she drives at night, and is nervous because the dashboard display is completely dark. Only thing that works when headlights are on, is turnsignal indicators, green, they still work.

Adjustment of dimmer switch, no help. Anyway, I told him this site is a gathering of Aerostar Gurus worldwide, someone here might have an idea.

Thanks guys, very much. Ed

 

I should also mention, that when he turns the headlights OFF, the digital readout for MPH, guage readouts, all return back to normal on the digital dash.

It also cuts out when parking lights are turned on, but the parking lights work fine. Just no readout via the dashboard, completely blank / black.

Thank You/. Ed

 

I had a similar symtom -- for years. In my case ('89 XLT), I would be driving along at night, and the dash would go dark. Sometimes for minutes, sometimes longer. In some cases, flicking the HL switch ON/OFF a couple of times would re-light the display in the HL ON mode.

Eventually, after studying the schematic and living with it for years, I shotgunned the problem and ordered a "Nighttime Illumination Relay", a digital-dash-only part. Problem solved.

The purpose of this relay is to insert a resistance into the dash illumination during HL ON. That is, the dash lights on the digital dash are ON at all times that the key is ON, but with the HLs ON the dash lights are run at a reduced voltage to dim them. The "Nighttime Illumination Relay" does that task.

When I tried to order it, the dealer had a hard time trying to ID it. I eventually pulled it out and read the number off it to him, and it is a relay that is apparently used in other areas, because it was in stock. It was not terribly expensive.

Unfortunately, though I did save the part No., when I sold the van I gave the paperwork to the new owner, so I no longer have that number.

The NIR is not in the cluster, it's behind and below it.

 

AL, Thank You for the great post, with very useful information. I am printing out your reply right now, to give to my friend, as well as keeping a copy for myself. (I have an Aerostar with the digital dash as well).

Thanks again.
Ed

 

OK, I had the wrong name for it (from memory). I just looked it up, and it's real name is apparently "Day/Night Illumination Relay". I've glued together some 1989 Electronic Cluster diagrams and put the relay in red in the pics below. Be warned: these are large pictures.

First pic shows the relay as it relates to its feed from the main HL switch. The diagram shows only the relay's coil side, not its outputs.

Second pic shows how it relates to the cluster lamps.

Third pic is a component location pic, showing its approximate location in the dash.

(click on any image for larger)




BTW, because I no longer have an early Aero (my '93 has the later dash), I am giving away my spare JY-sourced early digital cluster. Condition unknown, pulled from a JY rig. You pay shipping (from 98368), it's yours:



Also have an analog cluster that's probably had all the gauges burned out of it from an overcharging alternator. Same deal:

 

There is another place to check, before dismantling the dash. The instrument panel dimmer control has a thermal fuse in it. It happened to me the first time I tried to dim the instrument panel, and that fuse blew. So the panel would only light up when the headlight switch is OFF. It's another brilliant Ford design; the dimmer is nothing more than a rheostat that changes the resistance in the circuit. If you set it close to full brightness, it has lower resistance, but the circuit draws the most current. Since the dissipated power is R*I^2, this is where the rheostat gets the hottest, and most likely to blow that thermal fuse.

I took the control apart to bypass that fuse, and just never use the dimmer function anymore (Always on full brightness). But I did find a replacement from the scrap yard that I will install if the old one ever does burn up.

 

Good point. I had the dimmer meltdown on mine ('89) as well. When I called Ford, it was NLA (three years ago). From memory, it's different for the digital dash than the analog. I, too, got one from the JY.