When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Looking for help. 1998 C5 coupe and the headlights won't open. Trying to repair for my deceased friends widow. Owned a C5 form 2003-2019, so very familiar with the platform.
Here's what I've done/checked:
Checked all applicable fuses
Battery voltage is at 12.4, marginal as car has been sitting. But problem persists when car is running and voltage at 13.2
Replaced headlight control module
Replaced headlight turn signal switch
Headlights work, which I understand take turn signal switch out of picture
Both motors open and close when 12 volts is applied directly to plug
Checked and confirmed module ground is OK
Confirmed 12 volts at motor plug wires. Both open/close wires at 12V positive
Thinking possibly received bad control module from EBAY and it's not giving motors path to ground. Any other ideas would be appreciated
Thanks, Mark
The headlights buckets won’t open or close if the ground (G102) is bad…have you checked that ??….so you applied 12 volts and a ground at the connectors???…looks like you’ll have to open up SP100 and terminal D is the ground…if you have a piercing probe you can pierce the ground wire and attach the wire to a clean ground and see if it works…the ground carries the current from the motors back to battery ground…if high resistance the motors will not get the full current…having 12 volts at the connector tells you nothing…current has to be flowing to check…you should also check for a voltage drop on the positive side of the circuit also and must be done when current is flowing.
Thanks for the response. I did check the ground I believe. With 5 pin connector removed from control module, had 3 ohms from grd wire on connector to grd landing G102. Leads me to believe relay in headlight module not closing contacts for path to grd.
Originally Posted by C5 Diag
The headlights buckets won’t open or close if the ground (G102) is bad…have you checked that ??….so you applied 12 volts and a ground at the connectors???…looks like you’ll have to open up SP100 and terminal D is the ground…if you have a piercing probe you can pierce the ground wire and attach the wire to a clean ground and see if it works…the ground carries the current from the motors back to battery ground…if high resistance the motors will not get the full current…having 12 volts at the connector tells you nothing…current has to be flowing to check…you should also check for a voltage drop on the positive side of the circuit also and must be done when current is flowing.
Resistance checking of a ground (static testing) is not the correct way…you can have half of the copper strands missing and you will still show the same resistance…you must voltage drop with current flowing…this is dynamic testing !!..watch the video…you voltage drop both positive and negative sides of the circuit…just think of your voltmeter as a “difference meter”…you can probe between the fuse and the positive side of the headlight connector…if you see 7 volts that means you only have 5 volts going to the headlight motor…you are “dropping” 7 volts…this is electrical 101…unfortunately 99.9% of professional mechanics don’t understand this concept…BTW, I would not buy anything electrical off EBay or Amazon !!!
Still struggling with this. New light switch, new module, but headlights still not opening. When operating headlight switch, cannot hear relay coil inside headlight module pick up.
Looks like you changed a bunch of parts without doing some electrical checks…if this checking is over your head seek out an auto electrical specialist !!…unfortunately we can’t guide you step by step.
If you are using the door opening guide step 3 using “continuity” is NOT how a ground is checked…I guess the engineers that came up with this guide were not electrical engineers…watch the video.
Found my issue. Thanks to "C5 Diag" for posting troubleshooting guide for headlight motor troubles. Guide took me to the "underhood electrical center", where I found 3 critter eaten wires. Had to remove the fuse panel to find the issue, which wasn't much fun, but was successful.
OK I am sorry if this comes off as a stupid questions the guild in the above slides says it is for a 1998 Corvette will it work for a 2003 Z06. I do not see why they would not be the same.
Headlamps not Opening/Closing
Found my issue. Thanks to "C5 Diag" for posting troubleshooting guide for headlight motor troubles. Guide took me to the "underhood electrical center", where I found 3 critter eaten wires. Had to remove the fuse panel to find the issue, which wasn't much fun, but was successful. 
