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Headlight Door Module Information


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This post is to document differences between the headlight door module (HDM) used in 88, 89 Reattas vs 90, 91 Reattas. Since this information is not readily available in the documentation, I think this post is a good way to make it available via a search for future reference.

The module used in the 80s is PN 16509097.

The module used after a believed running change in wiring in 90s and in 91s is PN 16525685.

The differences between the two are internal and I believe they can be used interchangeably in any Reatta. If this proves to be false this statement will be removed.

The 80s version uses current sensing to control the running of the motors, and the later version uses pulsed power and voltage sensing to do that function and has a timeout function so that after 6 seconds the motors stop running even if they haven't hit the end of travel stop of the bucket.

Also believe the signals that needed to be applied to the module at C1 "A" and "C" are the same.

Putting 12v on A will raise doors.

Removing 12v from A and grounding C will lower doors.

Application of 12v on C as well as A when headlights are turned on does nothing, but is done with stock wiring in all years.

Grounding of pin C is accomplished via the headlight filaments in the stock wiring, and if both headlights are burned out or removed, the doors will not lower.

Putting 12v on pin A but not on pin C which is accomplished in 80s with a diode, will keep headlights up but not on, even with ground on pin C.

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Check carefully all over the plastic body to see if there is a number molded into it.

As to whether they would work or not is anyone's guess. The link to the Fiero forum in the other headlight thread from wss944 shows:

16523917 for 97-04 vet, 87-89 firebird, Fiero , 86-94 sunbird and 86-89 skyhawk.

16521291 86 Vet. reversing the signal wires for fiero

16525685 90-94 Sunbird, 90-02 Firebird, 90-92 Toronado and 90-92 Buick Reatta. That module will not interchange with the Fiero.

16507923 16507924 87-92 TransAm - Firebird.

16505400 87-88 firebird.

16521297 90-96 Vet.

16510537 88-96 Vet.

16509097 198? firebird 1989 Reatta

They all work differently in some way or another from each other. That statement that the 90s Reatta won't work in a Fiero while the 80s apparently has me worried a bit.

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#16525685 '90-92 Reatta? That would be rarer then a '91 Polo Green vert. We should put Steve on that. I'll bet they are stored in the same garage...

But if I had to guess I would say the ones I have are from the '8? Firebird as that is all they have out at Gibson's at the time I was looking for them.

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All of the HDM identification is internal - unit must be opened and re-sealed. In a prior post, I mentioned information from my source that reflected distinguishing internal Product Numbers - will have to check and re-post for this thread. On my bench test stand, it was quite easy - 30 seconds - to test Pontiac modules. Either the headlights functioned thus the HDM was good or otherwise non interchangeable or just plain bad.

I just opened up a HDM and will try to send pictures top and bottom of the board. Only ID for the board is the number 16521089-6. The Omron relay has a removable cover and it would appear that the contacts could be cleaned up. A year or so ago, I tried to trace the OMRON relay for availability but was unsuccessful and doubt that the situation would be any better today. I have a collection of both Reatta and Fiero/Sunbird /?? modules and am sorry to say that I cannot positively say what the application for this one was.

The bottom half of the module board holder, and through which the 9 contact pins protrude, shows GM part number GM 16505537 4 L and the bottom plate which must be removed for access, is GM 16505538 2 D.

Pictures coming forth later today.

NOTE: This post modifies my previous one


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Good info Kingsley.

I have not ever taken much of a look at one. They don't cause trouble very often.

Nice to know they can be opened up and played with. I thought they were probably potted and sealed like a lot of modules are and therefore untouchable.

While there are probably many available at P&Ps, only a select few will work in a Reatta.

Need to figure out how to identify the ones that are so they can be saved.

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At about noon today, I finally started my grand *clean out and organize the garage* project. As is usually the case, after getting started and loading the pickup with some scrap wood and drywall, I got sidetracked. I installed a condensate auto-drain on my compressor. While doing that, I found dried and brittle insulation on the unloader pressure switch so, I changed out the wiring on that. That brings me to about 6:30pm (quitting time). Somewhere along the way I found a HDM (at least I believe it to be) from my dismantled '88 Reatta. I took some pics of it and posted them below to add to the pool of info. The part number sticker is pretty ratty and the last two (three?) digits are pretty well faded. Looks like 165090... 9?... 7?... maybe?







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Here are the pictures I mentioned in an earlier post.


These words are showing on the side: CONTACT: 6A 240 VAC 6A 28VDC COIL 9 VDC 16509987

On the top there is a schematic on the top for 14 pins - three rows of 4 pins each plus 1 row of 2 pins which coincides with the bottom of the PCB. Also "9V"

The mastic used between the two halves serves the purpose of a sealant and an adhesive and is really tough stuff.







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The GM PN molded into the plastic case crosses to a 3 generation Firebird.

The PN on IC1 seems to be a voltage regulator. Would be hard to find locally in small quantities, but china seems to be willing to supply them in the 1,000s. Couldn't find a data sheet.

Relay is a 4PDT. Might be hard to find a match that will fit.

Looks like getting case apart and getting parts would be hardest part of working on these.

Judging by the chip being a voltage regulator, this might be close to the 90s Reatta version.

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I just got back from Gibson's. Found an '87 Firebird and grabbed the HDM. None of these units have part #'s on the outside. What is up with that?

BTW the HDM on a Firebird is easy to spot and remove. It is located on the firewall right next to the Master Cylinder. Just unplug it and slide it off the mounting bracket. Not buried anywhere, just out in the open, easy to get at.

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Looking to capture some of the information from the other headlight thread.

The 80s and 90s HDMs should be interchangeable in a Reatta. (16509097 + 16525685)

It looks like HDMs from 80s Firebirds and Fieros will not work in a Reatta.

HDMs from 90s Firebirds should work.

No word from Vet owners as to if any of theirs would work in a Reatta.

Too bad they didn't mold the PN into all of the cases, as that paper sticker has fallen off most of them by now.

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Actually a HDM from an '86-88 Fiero does work. I was selling them to an associate of Kingsleys. I will try the ones I sent along with Hal [2seater] in my cars. Then go from there. Good thing there are more Firebirds at Gibsons...

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Thought I would add that the relay does not look like it should be too difficult to source. 9vdc is a bit odd, but 4PDT in a PCB mount form factor as pictured is rather common. I use this same relay type with a 24vdc coil routinely in repairs on old Hi-Fi gear. Omron is the usual supplier.


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It was a good afternoon today.

I stopped by the local Pick-N-Pull and pulled a HDM from a '91 Firebird. Has the little blue "REPLACE DO NOT REPAIR" decal, which also indicates part #16514174. Interestingly, this part # does not appear in the list above.

On the way home, stopped by a car show - where Kitskaboodle was showing one of his Fieros. We had a good time walking around looking at the various rods, '60s muscle cars, and other classics. I think Kit was more interested in the '52 VW Beetle than anything else. The only Buick we saw was a '49 Special Coupe, rodded with a SBC, TH350, Ford rear end, disk brakes, etc. His next project is to replace the TH350 with a 4L60 to get an overdrive, and re-gear the rear as appropriate.

Once home, dived into the HDM in my Reatta. (Ronnie - I will write up the procedure for you one of these days.)The HDM in my '90 has an orange "REPLACE DO NOT REPAIR" decal with part #16509097 on it. This is the same as Machiner 55 reported and also the Fiero list in post #3 for the '89 Reatta. It also correlates with the part # in the Illustrations pdf for '88-'91 Reattas. His info for '90-'91 Reatta is therefore wrong - at least for '90.

The Firebird HDM works perfectly in my '90. So we now have a second source for HDMs.

When I pulled the Firebird HDM, I also included the 4-pin and 5-pin connectors with good lengths of pigtail. So if anyone has questions, I can mess with it on my bench.

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Started the headlight relay mod on my '89 Reatta. Pulled the HDM just to verify the part #. Mine has the previously listed 16509097. The info is on an orange paper sticker that also states Replace Do No Repair. The external appearance is identical to the one that Machiner 55 posted above.

Just as a test, I verified that directly grounding the © input works as well as indirectly grounding it thru the headlight filaments.

David T

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Looks like my last post was a victim of the Syrian cyber attack.

In researching our HDMs I came up with the following.

16509097 was replaced by 16514174 around 1990 both are now obsolete.

16525685 was then used in Reattas (~90) and is still available.

By official cross references, it was also used in:

Buick Riviera 1986...1993

Pontaic Firebird 1982...1991

Firebird Formula 1993...2002

Firebird Trans Am 1992, 1998...2002

Oldsmobile Toronado (FWD) 1987...1992

Looks like it was also used in all Olds Trofeos and can be used in Lotus Elans and Esprits.

There are no official sources that verify it can be used in any Fieros or Corvettes. These will have to be verified by testing and then documented.

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The Headlight Module installed in a Buick Reatta is probably the most reliable component in the entire car. I have sold over 1000 headlight repair kits and not a single solitary customer has ever requested a Headlight Module. It is unfortunate but when a headlight mechanism is repaired with ill fitting or poorly constructed repair parts the headlight mechanism will bind up. This binding problem is then blamed on the headlight module and often times the problem is never solved.

If your car has never been modified or repaired with substandard parts, repairing a winking blinking headlight is an easy job. Contact me directly for more information.

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