Help electrical problem w T-84 Euro install
Thread Starter
Burning Brakes
Joined: Nov 2001
Posts: 1,162
Likes: 81
From: Bel Air MD
Help electrical problem w T-84 Euro install
Purcahsed T-84's from a forum member several months ago and tried to install today. I upgraded to a PIAA Extreme White bulb, but they still run on the standard H-4 55/60 watts. Installed one lamp and turned on to compare the difference to stock and the low beam did not come on, but the high beam would. It blew the 10 amp low beam fuse. I tried hooking up the other light to the other side with the regular H-4 bulb and it also blew the fuse on that side. Is it necessary to change the low beam fuse to a higher amperage? If so, what amp? Has anyone else had this problem? I have never read where anyone had a similar problem. My car is a 1999. Thanks for your help.
Tech Contributor
Joined: Dec 2003
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From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
When I fitted mine I went with the full harness from PFYC. It was plug and play and included relays to support the higher wattage bulbs.
http://www.pfyc.com/store/merchant.m...ode=VTLIGHTING
I didn't have any fuses blow at all.
http://www.pfyc.com/store/merchant.m...ode=VTLIGHTING
I didn't have any fuses blow at all.
Tech Contributor
Joined: Dec 2003
Posts: 19,384
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From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
Originally Posted by rwlc5
But the bulbs I have are not higher wattage bulbs. They are 55/60.
Tech Contributor
Joined: Dec 2003
Posts: 19,384
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From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
Originally Posted by rwlc5
I have a harness that connects the low & high beam inputs to a single H-4 out put. It is the harness for factory wattage.
My harness plugged into the passenger side low beam circuit abd the new H4 conenctors were run from that. I only had a live and a ground in addition to that as I recall.
The only thing I can suggest is checking out the harness with a multi meter to make sure you haven't got a short.
Melting Slicks
Joined: Nov 2004
Posts: 2,275
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From: Lake Oswego, Near Portland Oregon
The original headlights have 2 bulbs, each with 2 wire connectors. One of the 2 wires for each of those bulbs is at ground potenial. The other wire is the 12V plus, when the circuit is turned on. I cut off the 2 conductor connectors, and used an ohm meter between the battery negative, which is the car chassis 'gound' and each of the wires. The wires that indicate a low resistance are the grounds. I conneced the ground wire from the hi beam bundle to the ground wire on the low beam bundle. Now you have functionally 3 wires, a paired set for GND , a plus for HI and a plus for LOW. That is the 3 wires you need to operate an H4 bulb, and can be connected to a pigtail socket for H4 bulbs. I don't recall which terminal on the bulb is GND, HI and LOW. Perhaps a GOOGLE search can get you a diagram.
You should absolutely NOT blow fuses with the 55/60 watt version of the H4. I suspect the adapter harness you have is wired incorrectly, linking the + from one original harness bulb to the - of the other, which will be a direct short and blow the fuse.
H4 bulbs come in many wattages, 55/60, 60/100, 70/100, and even up to 100/120 and even 110/130. There are many bulbs available in Europe. I would NOT attempt to use the higher wattage H4s with the stock wiring, even if you put in bigger fuses, as the wire size is too small for really large current that high wattage bulbs will draw, as are the switches.. If you want to run the big watters, you will need to run a pair of very large wires from the battery + and -, such as 12 G or even 10G, to a set of high current relays, and on to the bulbs. The original headlight wires are extended to the relays and become the 'control' signal to operate the relay, which in turn turns on the lights. Resist the temptation to use the chassis as a 'ground' conductor. Using fat copper wire direct to the battery accessory terminals for the ground is always a better idea than trying to find a local grounding point. Big copper wire with a minimum of connectors is ALWAYS superior to the many connections/bonding and steel frame of traditional 'grounded' wiring.
I have run the T-84s and H4s in my 98 for about a year now with no ill effects. Great lamps! In fact I have used H4 based lighting in most all my cars since 1969. Over those many years I have run just about every wattage variation of H4 ever available, even having super high wattage bulbs sent in from Germany and France that were never sold in the US. The ones over 100 watts burn really hot and don't last too long. If you do a lot of night driving, you might get only 3 to 6 months out of them. The 55/60s will last for years.
GOOD LUCK!
You should absolutely NOT blow fuses with the 55/60 watt version of the H4. I suspect the adapter harness you have is wired incorrectly, linking the + from one original harness bulb to the - of the other, which will be a direct short and blow the fuse.
H4 bulbs come in many wattages, 55/60, 60/100, 70/100, and even up to 100/120 and even 110/130. There are many bulbs available in Europe. I would NOT attempt to use the higher wattage H4s with the stock wiring, even if you put in bigger fuses, as the wire size is too small for really large current that high wattage bulbs will draw, as are the switches.. If you want to run the big watters, you will need to run a pair of very large wires from the battery + and -, such as 12 G or even 10G, to a set of high current relays, and on to the bulbs. The original headlight wires are extended to the relays and become the 'control' signal to operate the relay, which in turn turns on the lights. Resist the temptation to use the chassis as a 'ground' conductor. Using fat copper wire direct to the battery accessory terminals for the ground is always a better idea than trying to find a local grounding point. Big copper wire with a minimum of connectors is ALWAYS superior to the many connections/bonding and steel frame of traditional 'grounded' wiring.
I have run the T-84s and H4s in my 98 for about a year now with no ill effects. Great lamps! In fact I have used H4 based lighting in most all my cars since 1969. Over those many years I have run just about every wattage variation of H4 ever available, even having super high wattage bulbs sent in from Germany and France that were never sold in the US. The ones over 100 watts burn really hot and don't last too long. If you do a lot of night driving, you might get only 3 to 6 months out of them. The 55/60s will last for years.
GOOD LUCK!
Last edited by FiberglassFan; Mar 26, 2006 at 04:27 AM.
Tech Contributor
Joined: Dec 2003
Posts: 19,384
Likes: 87
From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
Originally Posted by FiberglassFan
The original headlights have 2 bulbs, each with 2 wire connectors. One of the 2 wires for each of those bulbs is at ground potenial. The other wire is the 12V plus, when the circuit is turned on. I cut off the 2 conductor connectors, and used an ohm meter between the battery negative, which is the car chassis 'gound' and each of the wires. The wires that indicate a low resistance are the grounds. I conneced the ground wire from the hi beam bundle to the ground wire on the low beam bundle. Now you have functionally 3 wires, a paired set for GND , a plus for HI and a plus for LOW. That is the 3 wires you need to operate an H4 bulb, and can be connected to a pigtail socket for H4 bulbs. I don't recall which terminal on the bulb is GND, HI and LOW. Perhaps a GOOGLE search can get you a diagram.
You should absolutely NOT blow fuses with the 55/60 watt version of the H4. I suspect the adapter harness you have is wired incorrectly, linking the + from one original harness bulb to the - of the other, which will be a direct short and blow the fuse.
H4 bulbs come in many wattages, 55/60, 60/100, 70/100, and even up to 100/120 and even 110/130. There are many bulbs available in Europe. I would NOT attempt to use the higher wattage H4s with the stock wiring, even if you put in bigger fuses, as the wire size is too small for really large current that high wattage bulbs will draw, as are the switches.. If you want to run the big watters, you will need to run a pair of very large wires from the battery + and -, such as 12 G or even 10G, to a set of high current relays, and on to the bulbs. The original headlight wires are extended to the relays and become the 'control' signal to operate the relay, which in turn turns on the lights. Resist the temptation to use the chassis as a 'ground' conductor. Using fat copper wire direct to the battery accessory terminals for the ground is always a better idea than trying to find a local grounding point. Big copper wire with a minimum of connectors is ALWAYS superior to the many connections/bonding and steel frame of traditional 'grounded' wiring.
I have run the T-84s and H4s in my 98 for about a year now with no ill effects. Great lamps! In fact I have used H4 based lighting in most all my cars since 1969. Over those many years I have run just about every wattage variation of H4 ever available, even having super high wattage bulbs sent in from Germany and France that were never sold in the US. The ones over 100 watts burn really hot and don't last too long. If you do a lot of night driving, you might get only 3 to 6 months out of them. The 55/60s will last for years.
GOOD LUCK!
You should absolutely NOT blow fuses with the 55/60 watt version of the H4. I suspect the adapter harness you have is wired incorrectly, linking the + from one original harness bulb to the - of the other, which will be a direct short and blow the fuse.
H4 bulbs come in many wattages, 55/60, 60/100, 70/100, and even up to 100/120 and even 110/130. There are many bulbs available in Europe. I would NOT attempt to use the higher wattage H4s with the stock wiring, even if you put in bigger fuses, as the wire size is too small for really large current that high wattage bulbs will draw, as are the switches.. If you want to run the big watters, you will need to run a pair of very large wires from the battery + and -, such as 12 G or even 10G, to a set of high current relays, and on to the bulbs. The original headlight wires are extended to the relays and become the 'control' signal to operate the relay, which in turn turns on the lights. Resist the temptation to use the chassis as a 'ground' conductor. Using fat copper wire direct to the battery accessory terminals for the ground is always a better idea than trying to find a local grounding point. Big copper wire with a minimum of connectors is ALWAYS superior to the many connections/bonding and steel frame of traditional 'grounded' wiring.
I have run the T-84s and H4s in my 98 for about a year now with no ill effects. Great lamps! In fact I have used H4 based lighting in most all my cars since 1969. Over those many years I have run just about every wattage variation of H4 ever available, even having super high wattage bulbs sent in from Germany and France that were never sold in the US. The ones over 100 watts burn really hot and don't last too long. If you do a lot of night driving, you might get only 3 to 6 months out of them. The 55/60s will last for years.
GOOD LUCK!
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Tech Contributor
Joined: Dec 2003
Posts: 19,384
Likes: 87
From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
rwlc5,
Brian at PFYC sells the upgraded harness for $110 and he's a Forum vendor. Given Jennifers advice, that would give you the option to try alternative bulbs and improve the performance. If you have a duff harness it would cut out the hassle of fault finding.
His full kit comes with 135/90s which would certainly improve the lighting over stock. I'm actually running low wattage bulbs at present. I have T85s fitted for my return to UK and I don't want to dazzle oncoming drivers even around town. I'm holding back on the hi watt lights until I get back to UK. I'll be interested to see how long they last and whether they are worth the extra money for regular use.
Brian at PFYC sells the upgraded harness for $110 and he's a Forum vendor. Given Jennifers advice, that would give you the option to try alternative bulbs and improve the performance. If you have a duff harness it would cut out the hassle of fault finding.
His full kit comes with 135/90s which would certainly improve the lighting over stock. I'm actually running low wattage bulbs at present. I have T85s fitted for my return to UK and I don't want to dazzle oncoming drivers even around town. I'm holding back on the hi watt lights until I get back to UK. I'll be interested to see how long they last and whether they are worth the extra money for regular use.
Thread Starter
Burning Brakes
Joined: Nov 2001
Posts: 1,162
Likes: 81
From: Bel Air MD
It sounds like there is a problem with the wiring in the adapter harness that i have. I will have to figure out which are the gound wires from the factory low & high beams and make sure that they are paired together to the correct wire in the H-4 connector. If anyone knows how the wires should be connected, the info would be greatly appreciated. Thanks Jennifer for some great info.
Le Mans Master
Joined: Jan 2003
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From: AKA Harvey Mushman-I know just enough to be dangerous "Those who sacrifice liberty for safety deserve neither"- B. Franklin
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Originally Posted by FiberglassFan
If you want to run the big watters, you will need to run a pair of very large wires from the battery + and -, such as 12 G or even 10G, to a set of high current relays, and on to the bulbs. The original headlight wires are extended to the relays and become the 'control' signal to operate the relay, which in turn turns on the lights.
That's what I did for my 100/120s.Here are some more C5 lighting links.
http://www.c5forum.com/diy/eurolights.php
http://forums.corvetteforum.com/show...hlight=dummies
http://www.danielsternlighting.com/
http://www.rallylights.com/useful_in...amp_wiring.htm