using relays in place of the headlight motor control module (Page 1/4)
qwikgta JAN 12, 07:40 PM
OK, so i have used the search and found some data that is close to what I'm looking to do but here is the issue. The other day my headlight motors stopped working. I checked the motors using a 12V source and they go up and down just fine, nothing interfering with their movement. I have checked the switch and its also good. I have 12V at the switch, and the lights work just fine. I'm 100% sure its the control module. I realize they are easy to swap out but hard to find, even if you find one used, it may be bad. So looking at the wiring diagram in the 88 manual it seems that I could just run a set of 5 wire relays up, power to both sides w/ a switch that stays in a neutral position so no power will be lost.

In my thinking it would work just like power windows, you push the button "up" for the motors to have power and go "up". when they are up you let go of the button. Same thing for going down. Again, its just like power windows. Button in the neutral posit would not do anything and there would not be a power drain.

I know it would require another switch, but I have a blank spot under the power trunk lock switch, so putting a button on the dash is no issue. The old light switch will just be used for turning on the lights.

This is the diagram I came up with (with help from the internet)



Thanks in advance.

Rob

[This message has been edited by qwikgta (edited 02-05-2020).]

theogre JAN 13, 12:30 AM
See my Cave, Gen 2 HL Motor

Any Manual method to "replace" the module is a bad idea.
Motors have "Shear pins" to break for overloaded for jams, End of Travel, etc. and more so if module has problems covered in cave etc.
This pins die for that and old age.
If you or anyone put aftermarket Delrin pins in them then often just a matter of time the gears etc break because they are the weak part now. That before adding switches relays or whatever. see http://www.fiero.nl/forum/Forum2/HTML/128600.html

Module sees jam/EoT loads and kill power to the motors in microseconds.
You only turn off in 1-2 seconds and "beats up" the motors and rest of HL lifts electrically and mechanically every time you do.
Motors running only uses 3 to 4 amps max. Unmanaged stall can draw 3x to 5x that and burns out the motor.

"Bad" module can be a lot of issues.
Iffy wiring to it is a big one.
Crack solder at big pins on the board that wire plugs into is another. Reflowing solder there needs 25w at bare minimum, high gun/iron is better to heat fast w/o damage the board. Rest of board needs 25w iron or less because most joists are very small.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

FX JAN 13, 10:35 AM
If you're talking about the isolation relay as the 'control module', Rodney Dickman makes them up. I bought one for my 86 and it works as it should...
olejoedad JAN 13, 11:39 AM
He has the Gen 2 headlights.....
Larryinkc JAN 13, 03:10 PM
I have an 88 also and so far my headlight module works. If it fails my plan is to buy one of the new repro modules for 88 to 96 Corvettes. They are part # 16523917 which is the superseded part # of the original Fiero part. They are available from several sources for around $160.00.
qwikgta JAN 13, 07:00 PM

quote
Originally posted by Larryinkc:

I have an 88 also and so far my headlight module works. If it fails my plan is to buy one of the new repro modules for 88 to 96 Corvettes. They are part # 16523917 which is the superseded part # of the original Fiero part. They are available from several sources for around $160.00.



yea, thats the point, they are $160 bucks. I have the relays, the wiring, the switch and I'd like to drive the car w/ out having the lights up all the time. If I can just wire up some relays and add a switch to the dash ... done. Plus if the damn things goes south again, i'm out another $160 bucks.

So i guess no input on the wiring part. I'll just wire it up and give it a try.

Rob
theogre JAN 13, 07:42 PM

quote
Originally posted by Larryinkc:
I have an 88 also and so far my headlight module works. If it fails my plan is to buy one of the new repro modules for 88 to 96 Corvettes. They are part # 16523917 which is the superseded part # of the original Fiero part. They are available from several sources for around $160.00.

Quick search GM list them as fitting Fiero and others...
just 1 Example: https://www.gmpartsgiant.co...module-16523917.html

Can find on Ebay, Eckler’s, etc for less money but even many GM parts dealers are Far less then TFS prices.

[This message has been edited by theogre (edited 01-13-2020).]

qwikgta FEB 05, 07:00 PM
For all who find this post, use the diagram above if you want to do this, i've added the second motor and updated the diagram. Green/Green together, and Gray/Gray together. I used a 5 pin power window switch from a Saturn (I liked the look over stock Fiero/Firebird style). The important part of the diagram is ground at 87A. I tried wiring it up a different way, and it would not work. The motors have to have one wire hot, the other ground to work. Wired up this way, 87A will remain grounded until the relay is energized which will allow power to travel from 87 to 30. Other side stay grounded.

On the dash, I removed the dimmer wheel, and pushed into the dash (i don't use it anyway) and cut a hole to fit the power window switch into it.

One switch opens/closes the headlights and the stock light switch turns them on/off.

Cost: $0 I had the two relay's, the wiring and the power window switch.
Save: $160 -$300 cost of a replacement module.

Cheers

Rob

[This message has been edited by qwikgta (edited 02-08-2020).]

Dennis LaGrua FEB 05, 07:08 PM
I believe that the OEM headlight motor module has a safety feature that either reverses or kills the circuit if it is overloaded by a motor jam. The electro-mechanical method with the relays does not offer any such thing.

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qwikgta FEB 05, 07:47 PM
OK, so what. I mean i'm sitting right there in the drivers seat. I need lights so I open the doors. They open. Then I put on the lights. If I was using the stock module and I went to open them and there was a "Jam", they would not open. If I hit the button and they don't open, they don't open and I stop pressing the button. I don't get why everyone is so negative to saving $300 bucks. I get that if your stock module works you don't need to do this, but if your module goes out, this is something you can do. Thats all. I get that its not the way PONTIAC designed it. The stock module is just a super smart relay. Look at the wire diagram, its just a relay with some smart stuff built in. This is just another way to do it, thats all.

Rob