V40 Electric Trailer Brake Wiring Problem

d_link · Jul 20th, 2007, 20:31

I first posted this in the V40 Classic area, but felt it might get a better response here.

We had to replace our 1995 855GLT with a newer Volvo (don't ask... Valet parking totaled the car). We purchased a Volvo Certified Used 2004 V40, since it would be easily capable of towing our folding trailer (less than 700kg loaded). I have already installed the Volvo trailer hitch and am running into great difficulty finding anyone at Volvo in the US who will give me any electrical diagrams or assistance on connecting my DrawTite Activator I electric brake controller to the stoplight switch on the brake pedal. The standard line from Volvocars in the US is that Volvo does not support electric brakes on their US cars. This is ridiculous, because their literature states that our V40 can tow only 1000 pounds without brakes and 2000 pounds WITH BRAKES. It appears that Volvo doesn't really want to help, even though this car is perfect for our needs as a tow vehicle.

Does anyone have any suggestions as to how to locate the correct wire off the foot brake stoplight switch for my requirements (and how I would know that it is the correct wire). Our local Volvo dealer quoted me nearly $400 to install my wiring and brake controller, but can't tell me how to determine which the correct wire might be, without damaging the Antilock brake system (or some other electrical system). Activator instructions tell me to find the "cold side" of the switch; the connection which is only "live" when the brake is depressed.

Any other suggestions?

JackT5 · Jul 21st, 2007, 23:30

If you already have the towbar fitted could you not connect into the brake light feed at the trailer lighting socket?

Rooster · Jul 21st, 2007, 23:52

Just conect it to the brake light circuit on your towbar, that only comes live when you press the brakes, hence why your brake lights come on

d_link · Jul 22nd, 2007, 01:58

There is no wiring at the towbar yet. The electric brake controller needs to be relatively close to the battery with separate and constant power from the positive lead. The controller requires a signal from the brake pedal switch. It will not work properly when connected to any wiring in the harness near the rear of the car, and specifically requires that the electric connections for the electric brakes come from either the brake pedal switch or within the steering column for some Ford models. I have been able to locate the switch, but have not yet tested the connections to find a "cold" connection (one which is not active until the pedal is depressed. I assume that there might be more than one cold connection, since I have been warned about connecting to the wrong wire, which might cause damage to SRS or antilock brake system functioning. I will try the test on Sunday and let this forum know how it goes. The full wiring will not be connected until Wednesday. I wish that Volvo in the US would support towing better than they do, but that probably won't change until Volvo is no longer owned by Ford (we can only hope).

Thank you for all your suggestions. It is unfortunate that the wiring is so varied from Europe to the US.

Rooster · Jul 24th, 2007, 23:32

From what you say i'm thinking the brake thing your talking about needs a high ampage feed to it and works via a relay that is conected to the brake pedal switch,

The system works by using the little feed from the brake pedal switch to switch the larger circuit that comes from the battery via a relay in the system, if this is the case then it won't matter where you get the feed from aslong as the big feed is got from the battery, i think the main reason why it tells you to get feed from the pedal switch is because some cars have a bulb failure on brake lights and taking a feed off them will throw a wobbly so it tells you to take a feed from pedal switch instead,

Am i somewhere close or do you have a wiring diagram for it

niloc · Jul 27th, 2007, 09:01

Quote:

Originally Posted by d_link

This is ridiculous, because their literature states that our V40 can tow only 1000 pounds without brakes and 2000 pounds WITH BRAKES.

....would that be over-run brakes (come on proportionatly when the drawbar is compressed; i.e. by the towing vehicle slowing down)?

malb · Jul 27th, 2007, 11:18

Niloc, in answer to the question posed in previous post, it should not make a difference whether you use hydraulic/mechanical overrun or electric brakes provided that the systems are properly set up and working efficiently.

Electrics as discussed will be applied as soon as any normal vehicle braking occurs, as with overrun systems.

Overall there is an advantage to electrics with some control systems which provide an additional driver operated control so that the driver can independantly apply trailer brakes only in the event that a caravan etc. develops a sway. This allows the combination's speed to be reduced using trailer braking only, safely eliminating the sway. Applying car brakes generally will exagerate the sway, and if the sway is speed generated, then attempting to accelerate will most likely lead to problems also.

Another benefit is the ability to quickly and easily adjust the overall braking capacity for load variations. For example, a trailer loaded to near the maximum permissable for the tow vehicle requires substantial trailer braking, but the same level of breaking applied to the same trailer once unloaded would most likely result in locking wheels and flat spotting tyres. With better electric controllers, it is an easy matter adjust the brake current to reflect the changed load condition.

d_link · Jul 28th, 2007, 19:37

Hello all,

We now have full wiring and our electric brakes in operation. It was a time consuming and expensive operation, however, it will be much less expensive for future Volvo towing candidates in our area.

1) The brake pedal switch, located near the top of the pedal, is a simple rheostat. The auto electric company was easily able to tap off a "cold" connection which only passes voltage when the pedal is pressed. Power comes from the battery which passes through a circuit-breaker attached to the apron on the inside of the fender wall. Manual operation allows the caravan/trailer brakes to be operated independently of the car brakes and the modulation can be altered via a thumb wheel above the manual slide bar.

2) Caravan/trailer lights/signals/brake lights are all operational, however, a powered 3-wire to 2-wire converter was necessary. USA trailers do not usually include separate brake, turn, and running bulbs, combining the 3 operations into two less efficient bulbs. Directly wiring these to the Volvo harness would have drawn too much power, causing warning lights to appear on our dash, stating that bulbs were out, or an electrical system failure. A simple converter will not work, causing too much of a voltage drop, while the powered converter maintains a steady signal, satisfying the Volvo electronics.

3) We were able to maintain our blade-type 7-pin USA system, which is unlike the round pin 7-pin Volvo connector. The USA connector has a spring-loaded center pin for 12-volts while the others are flat blades for lights, brakes, etc.

The total cost of the wiring was way too much. I am embarrassed to mention it here, but we were under a time constraint and found ourselves in the position of lab rats or guinea pigs, allowing the auto electric company in Sacramento, CA, to experiment with our 2004 V40 to find the best means to connect our wiring. We are still VERY UNHAPPY with Volvo USA who still refuse to support trailer brakes or wiring systems. Volvo V40 is an excellent tow vehicle for any trailer/caravan up to 2000 pounds, while the V70, S60, and XC series can tow 3500 pounds and up easily. While surge brakes would have been a possibility for some, our folding trailer came equipped with electric brakes able to be operated independently of the tow vehicle, helping in extreme braking situations or trailer sway problems with crosswinds or excessive tow speeds.

I hope that my information above will offer others assistance when needed. The auto electric company in Sacramento, California, which did the wiring was Lehr Auto Electric, if any USA forum members from our west coast require assistance. They have now performed this operation on a V40 and XC90.

Jul 20th, 2007, 20:31	#1
d_link New Member Last Online: Sep 19th, 2014 09:40 Join Date: Jul 2007 Location: Elk Grove	V40 Electric Trailer Brake Wiring Problem I first posted this in the V40 Classic area, but felt it might get a better response here. We had to replace our 1995 855GLT with a newer Volvo (don't ask... Valet parking totaled the car). We purchased a Volvo Certified Used 2004 V40, since it would be easily capable of towing our folding trailer (less than 700kg loaded). I have already installed the Volvo trailer hitch and am running into great difficulty finding anyone at Volvo in the US who will give me any electrical diagrams or assistance on connecting my DrawTite Activator I electric brake controller to the stoplight switch on the brake pedal. The standard line from Volvocars in the US is that Volvo does not support electric brakes on their US cars. This is ridiculous, because their literature states that our V40 can tow only 1000 pounds without brakes and 2000 pounds WITH BRAKES. It appears that Volvo doesn't really want to help, even though this car is perfect for our needs as a tow vehicle. Does anyone have any suggestions as to how to locate the correct wire off the foot brake stoplight switch for my requirements (and how I would know that it is the correct wire). Our local Volvo dealer quoted me nearly $400 to install my wiring and brake controller, but can't tell me how to determine which the correct wire might be, without damaging the Antilock brake system (or some other electrical system). Activator instructions tell me to find the "cold side" of the switch; the connection which is only "live" when the brake is depressed. Any other suggestions?

Jul 21st, 2007, 23:30	#2
JackT5 Member Last Online: Apr 22nd, 2008 22:26 Join Date: Dec 2002 Location: Grimsby	If you already have the towbar fitted could you not connect into the brake light feed at the trailer lighting socket? __________________ 2002 S80 D5 SE, 96 850 T5

Jul 21st, 2007, 23:52	#3
Rooster Speed freak Last Online: Apr 3rd, 2020 22:04 Join Date: Nov 2003 Location: Yorkshire	Just conect it to the brake light circuit on your towbar, that only comes live when you press the brakes, hence why your brake lights come on __________________ 04 XC90 D5 --- Big bus 00 pug 306HDi --- Run about 88 pug 309GTi --- Project track car 07 CB600 Hornet --- 2 wheel fun

Jul 22nd, 2007, 01:58	#4
d_link New Member Last Online: Sep 19th, 2014 09:40 Join Date: Jul 2007 Location: Elk Grove	No wiring exists yet at the towbar There is no wiring at the towbar yet. The electric brake controller needs to be relatively close to the battery with separate and constant power from the positive lead. The controller requires a signal from the brake pedal switch. It will not work properly when connected to any wiring in the harness near the rear of the car, and specifically requires that the electric connections for the electric brakes come from either the brake pedal switch or within the steering column for some Ford models. I have been able to locate the switch, but have not yet tested the connections to find a "cold" connection (one which is not active until the pedal is depressed. I assume that there might be more than one cold connection, since I have been warned about connecting to the wrong wire, which might cause damage to SRS or antilock brake system functioning. I will try the test on Sunday and let this forum know how it goes. The full wiring will not be connected until Wednesday. I wish that Volvo in the US would support towing better than they do, but that probably won't change until Volvo is no longer owned by Ford (we can only hope). Thank you for all your suggestions. It is unfortunate that the wiring is so varied from Europe to the US.

Jul 24th, 2007, 23:32	#5
Rooster Speed freak Last Online: Apr 3rd, 2020 22:04 Join Date: Nov 2003 Location: Yorkshire	From what you say i'm thinking the brake thing your talking about needs a high ampage feed to it and works via a relay that is conected to the brake pedal switch, The system works by using the little feed from the brake pedal switch to switch the larger circuit that comes from the battery via a relay in the system, if this is the case then it won't matter where you get the feed from aslong as the big feed is got from the battery, i think the main reason why it tells you to get feed from the pedal switch is because some cars have a bulb failure on brake lights and taking a feed off them will throw a wobbly so it tells you to take a feed from pedal switch instead, Am i somewhere close or do you have a wiring diagram for it __________________ 04 XC90 D5 --- Big bus 00 pug 306HDi --- Run about 88 pug 309GTi --- Project track car 07 CB600 Hornet --- 2 wheel fun

Jul 27th, 2007, 11:18	#7
malb Member Last Online: Dec 29th, 2013 11:04 Join Date: Apr 2007 Location: Melbourne	Niloc, in answer to the question posed in previous post, it should not make a difference whether you use hydraulic/mechanical overrun or electric brakes provided that the systems are properly set up and working efficiently. Electrics as discussed will be applied as soon as any normal vehicle braking occurs, as with overrun systems. Overall there is an advantage to electrics with some control systems which provide an additional driver operated control so that the driver can independantly apply trailer brakes only in the event that a caravan etc. develops a sway. This allows the combination's speed to be reduced using trailer braking only, safely eliminating the sway. Applying car brakes generally will exagerate the sway, and if the sway is speed generated, then attempting to accelerate will most likely lead to problems also. Another benefit is the ability to quickly and easily adjust the overall braking capacity for load variations. For example, a trailer loaded to near the maximum permissable for the tow vehicle requires substantial trailer braking, but the same level of breaking applied to the same trailer once unloaded would most likely result in locking wheels and flat spotting tyres. With better electric controllers, it is an easy matter adjust the brake current to reflect the changed load condition. __________________ Drive it till it drops... Then kick it back to life!!!

Jul 28th, 2007, 19:37	#8
d_link New Member Last Online: Sep 19th, 2014 09:40 Join Date: Jul 2007 Location: Elk Grove	V40 Electric Trailer Brake Wiring Problem--SOLVED Hello all, We now have full wiring and our electric brakes in operation. It was a time consuming and expensive operation, however, it will be much less expensive for future Volvo towing candidates in our area. 1) The brake pedal switch, located near the top of the pedal, is a simple rheostat. The auto electric company was easily able to tap off a "cold" connection which only passes voltage when the pedal is pressed. Power comes from the battery which passes through a circuit-breaker attached to the apron on the inside of the fender wall. Manual operation allows the caravan/trailer brakes to be operated independently of the car brakes and the modulation can be altered via a thumb wheel above the manual slide bar. 2) Caravan/trailer lights/signals/brake lights are all operational, however, a powered 3-wire to 2-wire converter was necessary. USA trailers do not usually include separate brake, turn, and running bulbs, combining the 3 operations into two less efficient bulbs. Directly wiring these to the Volvo harness would have drawn too much power, causing warning lights to appear on our dash, stating that bulbs were out, or an electrical system failure. A simple converter will not work, causing too much of a voltage drop, while the powered converter maintains a steady signal, satisfying the Volvo electronics. 3) We were able to maintain our blade-type 7-pin USA system, which is unlike the round pin 7-pin Volvo connector. The USA connector has a spring-loaded center pin for 12-volts while the others are flat blades for lights, brakes, etc. The total cost of the wiring was way too much. I am embarrassed to mention it here, but we were under a time constraint and found ourselves in the position of lab rats or guinea pigs, allowing the auto electric company in Sacramento, CA, to experiment with our 2004 V40 to find the best means to connect our wiring. We are still VERY UNHAPPY with Volvo USA who still refuse to support trailer brakes or wiring systems. Volvo V40 is an excellent tow vehicle for any trailer/caravan up to 2000 pounds, while the V70, S60, and XC series can tow 3500 pounds and up easily. While surge brakes would have been a possibility for some, our folding trailer came equipped with electric brakes able to be operated independently of the tow vehicle, helping in extreme braking situations or trailer sway problems with crosswinds or excessive tow speeds. I hope that my information above will offer others assistance when needed. The auto electric company in Sacramento, California, which did the wiring was Lehr Auto Electric, if any USA forum members from our west coast require assistance. They have now performed this operation on a V40 and XC90.

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