View Full Version : Electrical: amps rating headlight relay Auto-Lite HRB-4201

09-25-2012, 12:44 AM
I'm new to this forum. and have a question on the headlight relay Auto-Lite #HRB-4201 used in (I think) 1940-1941 Hudson/ 1939 Studebaker). How many amps is this relay rated for.
I've got a 1955 Plymouth suburban. The electrical system 6V. I have a 2V drop in the wiring. By using 2 relays, one for headlight and one for highbeam, I can shorten the wire length by about 5m (15 feet). Thus having more voltage at the light bulbs.
I need about 22-25 amps rating as the headlights are 55W.
I've seen that when you buy this relay there is also a fuse next to the relay. Is this a special one? Socket is shown on the right of the picture 1 and 3.
Picture downloaded from this seller, www.ebay.com/itm/Autol...0953131247 (http://www.ebay.com/itm/Autolite-HRB-4201-Headlight-Accessory-Relay-fits-39-Studebaker-40-41-Hudson-/110953131247)

09-25-2012, 09:10 AM
This has some tech info on that part but does not give the current rating of the contacts:


Amazes me that there was a expectation someone would take apart such a relay and adjust it! Similar items today are sealed and not serviceable.

I think I'd look for a Bosch 141-951-251 C SP as used for horn relays on old VW's. I would think easier to find in europe? They are a more modern type with plastic housing and blade tabs but what you are doing is not original anyway. Normally, a circuit breaker is used instead of a fuse with the headlights. That way, if there is a fault, the lights may flash on and off instead of being completely out. Supposedly a little safer since you do get a little bit of light! At least enough to pull off the road.

Research on that VW relays shows others have used it for headlights.

Dwain G.
09-25-2012, 10:52 PM
The 1955 Plymouth wiring diagram in Motor's Handbook doesn't show any circuit protection in the headlight wiring, but there must be a fuse or circuit breaker somewhere. Check your Plymouth shop manual or owner's guide. Use a fuse of the same value that will fit in the relay fuse holder.

09-26-2012, 12:28 AM
I know this is not in original to the Plymouth wiring but want to solve this problem and have the old looks, so I would like to stick to old relay's as they look better then the modern plastic one.
Where can I find the rating for this relay?

Dwain G.
09-26-2012, 11:13 AM
Try here............. http://www.mymopar.com/index.php?pid=25