What's the deal with waterproof relays?

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MagicBeans

MagicBeans

10 Year 15 Year
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May 22, 2007
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Virginia Beach, VA
I'm looking at wiring up all the accesories on the cruiser in the next few days, and I want to do things right the first time. After watching a recent 4x4 t.v. show, it was brought to my attention that relays are not impervious to the elements. So, I went about finding some for my build that were. What I found was that waterproof relays were typically a 'potted' construction with a lower half (lower half sold seperately) outfitted with a waterproof seal. Hella, and painless wiring being the major suppliers at a cost of approximately $40-50 a relay :eek:. Then I got to thinking of just using some di-electric grease on some normal ones, or just sealing them with hot glue... Then I found these Parts-Express.com:*12 VDC Waterproof 5-Pin Relay SPDT 30/40A with Metal Bracket | spdt relay automotive 12v bosch alarm for a whopping cost of $5 a relay. SO, what gives? Is it worth my time and money to spend $40 on a single relay? Should I just by a dozen $11 ones and replace them as they burn out? Are the $5 sealed ones legit? Any takers???
 
I think most relays are water-resistant to some extent. I'm guessing that the waterproof ones will continue to work when submerged in water for a long period of time??

I'd want to protect the wires going into the relay, especially if it's closer to the bottom of the truck where water crossings could soak the relay. $40-$50 is worth the peace of mind for me if thats the relay that starts my truck or runs the fuel pump.

Just my 2 cents.
 
My '92 Z-28 engine donor has weather-resistant relays OE. They are sealed at the plug to relay body with a silicone rubber seal, but I'm not sure that they are water-proof. They are not the typical 'sugar cube' relay and I think that they are unique to GM products, but I noticed a bunch of them on cars and trucks during my last junkyard foray. Would be simple enough to harvest the relays and their matching Weatherpack-like plugs.
 
A lot of relays are internally sealed against the elements, but the terminal pins are not. They plug into an open socket. You could put some di-eletric grease on the pins and that would probably last a long time. You might also consider an enclosed weather tight fuse/relay block (see my sig line below).
 
Thanks guys for all the input. I have also seen the OE relays that have a similiar construction as the hella's etc, and I would use those, but I would worry that I'm grabbing the wrong ones. Otherwise I'm just suprised that they would charge $40 for waterproofing the pin terminals on the bottom of a relay. IMO, it's not very often that terminal pins get shorted out because they are wet. I'm much more concerned with the guts inside the relay. That being said, I'm thinking the $5 sealed ones are a good deal.
 
It's not the "shorting out" of the relay pins that is typically the problem with relays and exposed pin terminals--it's corrosion. Get a little water, a little dirt, a little salt in there and in a few years you start to have problems. Di-electric grease will help forestall the problem, but with relays of this type in the engine bay you will eventually get corrosion. The $40 waterproof ones are probably in low demand, and hence the high price. Have you tried marine electric suppliers? I would imagine there is a little higher demand for waterproof relays on boats.

Also remember to factor in the cost of fuses and fuse holders with the cost of the relays and the cost of shipping when you are considering total cost.

BTW, my Aux fuse/relay panel averages out to $17 per relay/fuse combination (includes shipping), are weather tight, looks good and installation is simple and elegant--just two wires to connect per relay.
 
Last edited:
slcfj62 said:
BTW, my Aux fuse/relay panel averages out to $17 per relay/fuse combination (includes shipping), are weather tight, looks good and installation is simple and elegant--just two wires to connect per relay.
Click to expand...

Yeah, I do like your setup. If I hadn't already ordered about $45 worth of Bluesea fuse block I would probably go with your option. It seems pretty straightforward and clean. Good points about the terminals getting corroded too - but I've never had it happen on any of mine. I think I'm going to try out the $5 waterproof ones, although the hella potted ones do look cool. But I can't seem to find a good distributor for them either. Anyways, thanks :cheers:
 
A simple solution to the waterproof issue is to put the relays under the dash or other interior location.... If it's convenient

For the most part anything with "marine" attached to the name is more expensive (I work in a boat yard) Surprisingly the typical relays we seem to use for aux lights etc. on our cruisers are not used very often in the boats we work on, mostly 35 to 65 footers. I would have to ask one of the electricans why but my guess is that boats most of the time have a dedicated power distribution panel.

Tony
 
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