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TDR Application 2: Motorcycle HID Retrofit

Avoid Hot-Restrike or Starting Problems

Status: Units are built to order - Please expect up to 2-week delay after receipt of order until order is shipped


On many motorcycles, the headlights are left on at all times, including when the bike's engine is started. The HID system has a high current draw which reduces the battery current available for starting, which can cause starting problems especially in cold weather. On other bikes, the headlights are switched off during engine start, causing a "hot restrike", where lights turn on when the bike is first turned on, then turned off during engine starting, then quickly turned back on again after the engine is started. Hot restriking is not very good for the ballast or the HID bulb, reducing its lifespan significantly.

The WolstenTech Time-Delay Relay eliminates hot-restrike and starting problems by allowing the user to set an adjustable turn-on delay of 0 to 2 minutes. The ballast will not be powered on until this delay time has passed, so the HID system only starts after you have started your motorcycle.

Another benefit of the WolstenTech TDR is that it can be used to divert power for the headlights from going through the headlight dimmer switch. Some people who have upgraded to HIDs on their motorcycles have found their hi/lo switches' contacts corroding due to arcing, caused by the high start-up current used by HID systems. By using a WolstenTech TDR and wiring it so that the hi/lo switch is used only to trigger the TDR, this problem can be avoided. See Example 3 below for an example of this on an H4-type system, where each ballast has its own TDR-P and fuse. Note that the high-beam signal from the switch is still used to connect to the H4 HID kit, but this is only for powering the solenoid used by these kits to move the bulb and provide high-beam.

One more benefit of the WolstenTech TDR is if your bike stalls, perhaps in an intersection. On some bikes, the headlights are wired to cut out when you restart the engine, but this can be dangerous when restarting at night on the road, and sometimes HID ballasts may not refire properly. With the WolstenTech TDR controlling your headlights instead, they will stay on when you have to restart your engine after a stall, as long as you don't power cycle your ignition switch. Since HIDs don't use that much current when they're warmed up, and engines are easier to start when they're warmed up, this shouldn't cause any starting problems as there are when the bike and HIDs are cold.

Another important feature of the Time-Delay Relay is its extremely compact size. Space is very limited in motorcycles, and this relay is much smaller than most alternate solutions for this problem. You should have little trouble fitting the TDR into your motorcycle. It also includes two mounting holes for easy mounting, but if an even smaller size is needed, these can be cut off for a total length of only 1.5" or 39 mm.

The following features of the Time-Delay Relay serve to make retrofitting HID lights into motorcycles easier:

  • Compact size of 2.375" x 1.29" x 0.81" or 60 x 33 x 21 mm for fitting into the tight confines of a motorcycle.
  • An adjustable turn-on delay of up to 2 minutes, so that headlights will not turn on for some time after activating switch or starting motorcycle, eliminating hot-restrike.
  • An adjustable turn-off delay of up to 2 minutes, so that, if desired, headlights will stay on for some time after turning off headlight switch or motorcycle.
  • Two independent, isolated input connections for use in H4-equipped motorcycles.
  • Works with both positive and negative-switched headlight systems, so you don't have to worry about finding out which kind your vehicle is before ordering.

This relay is rated for a maximum current of 20A peak, and 10A continuous. A typical HID ballast uses around 6A at start-up, and settles to around 3A after a few seconds, so two ballasts are well within the power limits of this relay.

If you wish to have separate relays for the low and high beams, either because together they exceed the 10A current limit of the TDR, or you prefer the greater redundancy of separate relays, be sure to read Application 3.

How many?
Should you order one or two relays? That's something every customer will have to decide for him or herself. These relays can handle the power consumption of two 35W HID ballasts, so if you wish to use one relay for your whole headlight system, it will work just fine. Of course, if you have a motorcycle with only one ballast, only one relay is needed.

However, if you have two ballasts and desire maximum redundancy, you can use two relays, with two separate fuses, so that if one ballast or relay malfunctions, you still have one headlight functional. It is also possible to use one relay with two fuses, between the relay and the ballasts, to protect against ballast failure, though you will still lose both headlights if the relay fails (extremely unlikely, but it's important to be aware of all possibilities when planning a system for maximum reliability).

Please also see the Installation Instructions page for sample wiring diagrams showing how this relay can be installed in a typical car.


Example 1: Single H4-Type Headlight System with TDR

Single H4 Headlight Diagram


Example 2: Dual H4-Type Headlight System with Dual TDRs

Dual H4 Headlight Diagram


Example 3: Dual H4-Type Headlight System with Dual TDR-Ps

Dual H4 Headlight Diagram


Example 4: Dual Headlight System

Dual Headlight Diagram



Item Added!
Positive-Switching Time-Delay Relay (TDR-P)
Price: $32
Item Added!
Negative-Switching Time-Delay Relay (TDR)
Price: $32