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Doug, ASE Certified Technician
Category: Car
Satisfied Customers: 8594
Experience:  16 years automotive and OTR repair including specialized training from Toyota and Mitsubishi
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Ref: 1994 Fleetwood Bounder M36P (Cummins diesel/Oshkosh chassis):

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Ref: 1994 Fleetwood Bounder M36P (Cummins diesel/Oshkosh chassis): I converted the sealed beam headlights to H1/H4 elements. They work well for about 30 minutes when the begin flashing on/off with about 2 second cycles. Unable to locate a relay or breaker specific to headlights. Received wiring diagrams from Fleetwood but they dont show headlight switch or wiring between switch and fuse panel or fuse panel and wiring harnesses at headlights. I have the relay in hand that Hella recommends for this installation, but can't find where to put it.

The relay that is provided by Hella is for an auxillary power run. Hooking up the higher power lights directly will result in excess power draw that is unsafe for the existing wiring which is why you are having power problems as things heat up with extended use.

The relay provided needs to be hooked up so that the power feed to the headlights is connected to the relay on the load side then straight to a auxillary fuse then the battery. The feed previously going in to the head light needs to go to the control side of the relay, and the other end of the control side to 12V or ground (depending on the headlight switched input... it will be the opposite).
This needs to be done for both low and high beams, one relay each (tap to the headlight input prior to the split to both sides so you only need one low beam and one high beam relay)
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Customer: replied 4 years ago.

Doug: Thanks for the response. Any chance that you can direct me to some form of schematic or diagram that shows me how I can wire up the relays? The "relays" provided are about 3/4" cubes with 5 plug-in spades. I assume that some form of receptacle would be required. Would this be something available off-the-shelf? Or would some other type of relay be appropriate? Jerry

Hi Jerry,


You can buy receptacles for these relays or just use blade terminals to plug in (receptacle is more desirable of course).

I do not have access to a schematic for your vehicle, however the general configuration would be the same on any vehicle. The 3/4" 5 pin relays are standard "Bosch" type relays. They will be numbered somewhere on the relay to identify each pin. Pins 85 and 86 are your coil pins. Essentially, if your headlights are positive trigger like all vehicles basically, you would connect one of these to constant ground and the other to the headlight trigger signal (the wire that normally goes hot when you turn the switch on for whichever beam you are wiring) which would go positive when the switch is turned on. When this happens the coil of the relay has power and ground and it energizes.

Pin 30 on the relay would be your load power which would connect to a fuse then battery positive, using the recommended gauge of wire for the lights you chose.
Pin 87 is the output load which would then run 12V to each headlight positive input for the beam you are wiring, and the wire would need to split off to power both headlights (same beam) on the same relay feed. The headlight bulb would retain constant ground.

The same process would be repeated for the high beams, again using one relay to power both beams.

Here is a very nice illustration someone else has made to visualize what I described. You will see the factory wiring at the bottom going in to the relays as triggers on 86, the red new power feed fused going to pin 30 on each relay. The ground on pin 85 is shared with the headlight grounds in the illustration, though this is not necessary since you are working on a vehicle that uses a shared chassis ground.... 85 just needs to be grounded to chassis if that is easier.
Pins 87 show the output wiring to the appropriate headlight and beam on each side.


I just wanted to add, you can disregard the different design (4 headlight, 2 low 4 high configuration), something you won't be using on yours.... the illustration is primarily to show the items I described only. I didn't want that wire to cause any confusion.