Headlight Isolation relay
Thread Starter
Burning Brakes
Joined: Jun 2005
Posts: 871
Likes: 2
From: Orlando Fl
Headlight Isolation relay
Hi all...
I had a 18V power spike in my vette...
Now, my headlights won't raise up.
My vette is an 86, but the lighting was upograded by the previous owner to the 88+ style.
I acquired a motor relay (the one that sits ahead of the drivers side wheel well), and my light door motors still have no power to them.
In looking at the service manual (8A-14-2) it shows an isolation relay, but it seems to have no placement for it.
Anyone know where I should look?
Any other possible causes for this problem?
Thanks
I had a 18V power spike in my vette...
Now, my headlights won't raise up.
My vette is an 86, but the lighting was upograded by the previous owner to the 88+ style.
I acquired a motor relay (the one that sits ahead of the drivers side wheel well), and my light door motors still have no power to them.
In looking at the service manual (8A-14-2) it shows an isolation relay, but it seems to have no placement for it.
Anyone know where I should look?
Any other possible causes for this problem?
Thanks
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
The two headlight relays and isolation relay are located in the driverside headlight well. Next to the evap canister. They came stock with a black cover over them. The isolation relay is the one in the middle, IIRC.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
If the conversion to the 88 and later style included the later one-piece relay, it is a single non-servicable component. Look for a single black box about 4"x4" by about 2" high in the left headlamp well. The new system used an electronic version and there are no mechanical parts like the early relays had.
Thread Starter
Burning Brakes
Joined: Jun 2005
Posts: 871
Likes: 2
From: Orlando Fl
RRT: Great link.. thanks
OK.. The One piece relay is what I got from Redrose, and he told me it was tested good several months ago.
I can see 12 volts into it, but not out. I'm not sure Im checking the right wires
Anyone know that pinouts, and what the voltage should be?
If its not the relay, what else could it be?
If the conversion to the 88 and later style included the later one-piece relay, it is a single non-servicable component. Look for a single black box about 4"x4" by about 2" high in the left headlamp well. The new system used an electronic version and there are no mechanical parts like the early relays had.
I can see 12 volts into it, but not out. I'm not sure Im checking the right wires
Anyone know that pinouts, and what the voltage should be?
If its not the relay, what else could it be?
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
headlice module wiring
88+ headlite motor control module replaces three relays on the early c4...both of the headlite motor relays and the isolation relay.
there are two connectors on the headlite module, a ''four pin'' and a ''five-pin''...terminal designations are cast in the plastic case alongside each connector.
four pin connector:
1) terminals A and B drive one headlite motor.
2) terminals C and D drive the other.
polarity changes to ''open'' or ''close'' headlite
five pin connector:
1) term A..12v+ only powered by headlite switch when ''on'', tells module to ''open sesame''...module output only continues as long as module senses''ripple'' on output circuit to motor, shuts power off when no ''ripple'' is detected, must go thru ''close'' signal cycle (see ''3'' below) before output will go to ''open'' again....(headlite switch in ''parking'' provides no signal to open or close)
2) term B..hot at all times, 12v+ fused.
3) term C..12v+ only when headlite switch is ''off'', tells module to reverse feed polarity of output to motors and close headlite...output is active until ''ripple'' ceases in output circuit
4) term D...ground
5) term E..hot at all times, 12v+ fused
note that the module does NOT limit current flow, and may smoke if motor current draw is excessive but motor is still running.
there are two connectors on the headlite module, a ''four pin'' and a ''five-pin''...terminal designations are cast in the plastic case alongside each connector.
four pin connector:
1) terminals A and B drive one headlite motor.
2) terminals C and D drive the other.
polarity changes to ''open'' or ''close'' headlite
five pin connector:
1) term A..12v+ only powered by headlite switch when ''on'', tells module to ''open sesame''...module output only continues as long as module senses''ripple'' on output circuit to motor, shuts power off when no ''ripple'' is detected, must go thru ''close'' signal cycle (see ''3'' below) before output will go to ''open'' again....(headlite switch in ''parking'' provides no signal to open or close)
2) term B..hot at all times, 12v+ fused.
3) term C..12v+ only when headlite switch is ''off'', tells module to reverse feed polarity of output to motors and close headlite...output is active until ''ripple'' ceases in output circuit
4) term D...ground
5) term E..hot at all times, 12v+ fused
note that the module does NOT limit current flow, and may smoke if motor current draw is excessive but motor is still running.
