1988 headlight trouble...again
Thread Starter
Intermediate
Joined: Mar 2015
Posts: 49
Likes: 3
From: Lima Ohio
1988 headlight trouble...again
I have an 88, 35th Anniv. model with a passenger side headlight that refuses to go up. I have replaced both side sets of bushings. It will open/close with the manual control, so I know the linkage is OK. Upon previous advice from the forum I had the motor rebuilt, still no work. My question is: Do I have the headlight relays($19.95)located on the driverside up in front of the tire, which I don't see or do I have the more, naturally, headlight actuator module($129.95). Most sites I see tell me that I have the relay but I can't find them. I would like to switch the relays and see if I can make the pass. side work. Also, can I jump the headlight motor from the battery to make sure it is working before shelling out for the actuator if that is what I have? Thanks in advance for any help.
Instructor
Joined: May 2009
Posts: 118
Likes: 16
From: Alexandria Kentucky
The electronic actuator is located in front of the left wheel well. It is a flat, box shaped affair, is mounted horizontally, is about 4 inches on a side and maybe 1.5 inches tall. There are a couple of connectors going to it.
If you have a Factory Service manual, and you are certain you have everything unplugged from the motor, you can apply power from the battery to the motor connector but first make sure of the color of the wires matches what the FSM shows so that you get the connector correct otherwise you risk the possibility of stripping the gears in the actuator by forcing the motor hard against the stop.
I would use the manual actuator control and park the headlight midway between the two extremes before applying power. Be ready to instantly remove power before the motor travels very far, reverse the wires, go again being ready to again instantly remove power. If you get travel both directions without any binding, the motor and gears are OK and the problem is either controller, relays, connectors or wiring.
If you have a Factory Service manual, and you are certain you have everything unplugged from the motor, you can apply power from the battery to the motor connector but first make sure of the color of the wires matches what the FSM shows so that you get the connector correct otherwise you risk the possibility of stripping the gears in the actuator by forcing the motor hard against the stop.
I would use the manual actuator control and park the headlight midway between the two extremes before applying power. Be ready to instantly remove power before the motor travels very far, reverse the wires, go again being ready to again instantly remove power. If you get travel both directions without any binding, the motor and gears are OK and the problem is either controller, relays, connectors or wiring.
Thread Starter
Intermediate
Joined: Mar 2015
Posts: 49
Likes: 3
From: Lima Ohio
C4-90...I saw that box you were talking about and figured that was the actuator. I'll try bypassing it using the manual operator as you suggested at half open. You go on to mention relays later in your post, are their relays also used along with the actuator and if so where are they located? Thanks again.
Instructor
Joined: May 2009
Posts: 118
Likes: 16
From: Alexandria Kentucky
No, it's electronic. The relay approach is part of a old tech electro-mechanical solution to the task of opening and closing the headlights whereas the actuator is all electronic control. It senses the increase in current draw when the motor hits the stop going either direction and biases the power transistors off without resorting to relays to actually cut the power. The MTBF is greater - in theory at least - than the electro-mechanical relay only system. (When I wrote my reply, I didn't know if you had a relay or electronic system so I added 'relays' to my potential points just to cover the bases.)
Last edited by C4-90-41001; Aug 8, 2017 at 02:24 PM.
Thread Starter
Intermediate
Joined: Mar 2015
Posts: 49
Likes: 3
From: Lima Ohio
C4-90...thank you for the explanation re: actuator. If the headlight would work when I bypass the actuator, would it be safe to assume that I need to replace the actuator? Looking online there does not appear to be any serviceable parts in the actuator.
Instructor
Joined: May 2009
Posts: 118
Likes: 16
From: Alexandria Kentucky
Order an actuator? Well, almost.
You should check out the condition of the wires and connectors first and use some contact cleaner on all connectors in the path from the battery to the headlight, including the inbound and outbound connections on the actuator.
If no joy finding anything wrong, see if you can measure 12 volts across the wires powering the motor when you operate the headlight retract/extend switch. If you do not see any voltage going to the headlight motor but there is voltage coming in to the actuator, spend the money then.
You might give Contemporary Corvettes in Pennsylvania a call and get a price on an actuator from them. It will be used but typically CC offers a 30 data warranty in case there is a problem and they are much cheaper than a new part. They are one of the largest Corvette salvage yards in the world - if not THE largest.
By the way, we've been calling the motor controller an actuator but the actual name is the Headlight Control Module. When you call someone to order one, you should call it that and also give the vendor the year of your 'Vette.
Best of luck.
You should check out the condition of the wires and connectors first and use some contact cleaner on all connectors in the path from the battery to the headlight, including the inbound and outbound connections on the actuator.
If no joy finding anything wrong, see if you can measure 12 volts across the wires powering the motor when you operate the headlight retract/extend switch. If you do not see any voltage going to the headlight motor but there is voltage coming in to the actuator, spend the money then.
You might give Contemporary Corvettes in Pennsylvania a call and get a price on an actuator from them. It will be used but typically CC offers a 30 data warranty in case there is a problem and they are much cheaper than a new part. They are one of the largest Corvette salvage yards in the world - if not THE largest.
By the way, we've been calling the motor controller an actuator but the actual name is the Headlight Control Module. When you call someone to order one, you should call it that and also give the vendor the year of your 'Vette.
Best of luck.
Last edited by C4-90-41001; Aug 8, 2017 at 05:36 PM.
