Join Date: Oct 2016
Location: LaHave, Nova Scotia, Canada
Just wanted to update all of you on the DRL issue.
First, special thanks to Z09B4U for the troubleshooting tips.
To recap the initial problem, I noticed that my HVAC fan speed was cycling ever so slightly in stop and go traffic and the stereo display was flickering in unison. Shortly afterwards the DRL stopped working and headlights would only work on high beams (parking lights were OK).
Trouble shooting had me running around in circles until I discovered a high resistance ground on the negative battery terminal cable. Cleaning this up had the DRL and headlights/parking lights functioning normally. To be safe I ran an alternator output test by switching on all the lights (incl. high beams), AC on high, foot on the brake, power antenna operating and power seat operating. Voltage at the battery never dropped below 13.65V.
To reduce the load on the headlight switch and the DRL Module I modified the circuit to uses relays (30A each). One for the DRLs and the other for the Headlights. The existing DRL and Headlight circuits trigger the relay coil (terminal 85 and 86). The power circuit for each relay (terminal 30 to 78) draws its power from the headlight fusible link (before the headlight switch). I know, it is a pain to replace if the fusible link blows - I have a circuit breaker that I can substitute when the time comes. Please note, I have bypassed the DRL Diode so the headlights receive the full 12V when the car is running and not the normal 10V. Now the headlights are a little brighter during the DRL operation.
The DRL and headlights work to my satisfaction. :-)
Hope it helps.
Thank you and take care,
1996 Impala SS (102K km - for sale as of May 2018), 1994 Ford Escort, 1981 Mercedes 300SD (SOLD), 1971 VW Beetle Convertible (next project).