Electrical Gurus help please

[G-ZUS]

I am trying to hook up heated seats in my car. My car did not come from the factory with leather or heated seats. I bought the seats from a v6 Accord of the same year (1999 Honda Accord coupe). I got the power seats hooked up but I am trying to hook up the seat heaters. I have a fuse for it in the under hood fuse box, after that it's non existant. (part in the red box in the diagram). I have the switch hooked up to the seat and all the grounds grounded etc. Just have to get power at the switch now

My questions are:
- Can I bypass that part and go straight to the fuse in the fuse box?
- What's the purpose of the relay?
- Can I get an aftermarket relay? Does it have to be a specific volatage etc


http://www.members.shaw.ca/malkadri/Diagram.jpg

[diamondedge]

From a general perspective, a relay is used to switch high currents when turned on. The relay basically works by having a smaller current close a big switch to allow big currents to flow.

The switch on your dash isn't capable of switching on a high current (unless it was a gigantic switch) so the switch on the dash switches on the tiny current (a few milliamps or more) to the relay, which then in turn closes to allow the bigger current to flow to the seat heaters.

1) So no, you can't skip that part. As well, the wires for the seat heater switch are not likely able to handle big current. How big is the fuse for your seat heaters? (Edit : 20A. You'll need that relay, pretty sure now.)

2) See explanation above

3) Aftermarket ones are fine - most are rated for 12V or so and will specify the current they can switch. I've seen as big as 30A.

Hope this helps.

[G-ZUS]

Where would I be able to a relay on the cheap?

[v2kai]

Originally posted by G-ZUS
Where would I be able to a relay on the cheap?

automotive 12VDC relay from thesource ( used to be radioshack)

[diamondedge]

PartSource, NAPA, Canadian Tire, any big name should have something to fit your needs.

[G-ZUS]

Sorry for the shitty camera phone pic. Hope it's readable. Would one of these relays be sufficient for the job? Is 14-16 gauge wire good enough? thats about the size of wire in the seats harness.


http://www.members.shaw.ca/malkadri/relays.jpg

[diamondedge]

20A fuse to cover both seats, theory says each seat draws an even 10A. I'd go with 14 AWG to be safe. The fuse has to blow before the wire melts :)

Googling that relay image FR-3309 tells me it's a turn signal relay, and looking at the pins, I have no idea how it works. Someone can chime in and confirm? Can't tell what the lower relay is, sorry.

You'll need a beefier relay, one that can switch at least 30 A (overrated to ensure it will work)

Edit, check out this site for information:

http://www.the12volt.com/relays/relays.asp

[G-ZUS]

I hooked it up, the seat got a little warm, then hooked it up straight to battery and same result. Am I missing something here? Could the heating element be done for?

[chkolny541]

^^ are you expecting the seat to be steamy hot? maybe thats all you get with those seats

[AE92_TreunoSC]

usually only half the grid works on older seats like that

[mr2mike]

Originally posted by G-ZUS
I hooked it up, the seat got a little warm, then hooked it up straight to battery and same result.

http://www.google.ca/search?q=weak+heated+seats&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

Seems like the norm.

[diamondedge]

Damn, sorry they didn't work as hot as you wished for...

[mr2mike]

I'm sure come winter, you will notice a difference. In -20, those seats will feel like a million bucks.

[diamondedge]

Originally posted by mr2mike
I'm sure come winter, you will notice a difference. In -20, those seats will feel like a million bucks.

Yeah, it may be more noticeable on colder days.

[G-ZUS]

A little warm is better then freezing cold leather. Thanks for the replies guys! If I were to hook the seat heaters directly to power. Would I put 12V at the white/red wire, and ground the white/blue wire

[mr2mike]

Looks to me (I looked quick though so someone could verify) that the solid black wires are what you ground.

white/red and white/blue are essentially the same wire in that it just turns on another heating element. So I think both the red and blue wires are 12V. As far as I can tell.

[diamondedge]

Originally posted by mr2mike
Looks to me (I looked quick though so someone could verify) that the solid black wires are what you ground.

white/red and white/blue are essentially the same wire in that it just turns on another heating element. So I think both the red and blue wires are 12V. As far as I can tell.


Yeah, looks that way here too. Notice on the diagram the black wire connects to a block that says "distribution ground" My only presumption is that goes somewhere to chassis, which is ground.

[G-ZUS]

That being said, can I connect them both to each other and connect to 12 V? or would that fry my heating elements?

[mr2mike]

Ok with you doing this, I would be more concerned with not having thick enough wires and they get too hot and melt the plastic sheathing. That being said, I think you went with 14 gauge wire. I think there was a mistake above and he meant to say go with 12 gauge just to be safe. The lower the gauge, the thicker the wire. But I think 14 gauge would be okay too.

Get a relay kit which AutoValue sells.
Just need 14 gauge and 30A like in the picture:
http://www.hho-unlimited.com/catalog/97eb_1_16_1.JPG
The kit lets you wire it in and then plug the relay into it.

Basically, you run the automotive switch to turn the relay on.
http://img214.imageshack.us/img214/5461/relay4ix.jpg

Run switch in line on the wire going to post 86, then ground wire off 85 post to chassis. This activates the relay to click on or off. As most automotive switches can't handle being run inline on a seat heater setup. If it's hooked right, you should hear it click and can check continuity between 30/51 & 87 and multimeter should beep when switch is on and stop when switch is off.

Then you could twist the white/blue and white/red wires like you talked about above and connect them both to the 30/51 post and the 12 V White/Green power source to post 87.
No worries that the seat will burn out with the two wires getting 12V. The drawings show they both get 12V with the seat switch on High.
Hope that helps.

[G-ZUS]

Originally posted by mr2mike
Ok with you doing this, I would be more concerned with not having thick enough wires and they get too hot and melt the plastic sheathing. That being said, I think you went with 14 gauge wire. I think there was a mistake above and he meant to say go with 12 gauge just to be safe. The lower the gauge, the thicker the wire. But I think 14 gauge would be okay too.

Get a relay kit which AutoValue sells.
Just need 14 gauge and 30A like in the picture:
http://www.hho-unlimited.com/catalog/97eb_1_16_1.JPG
The kit lets you wire it in and then plug the relay into it.

Basically, you run the automotive switch to turn the relay on.
http://img214.imageshack.us/img214/5461/relay4ix.jpg

Run switch in line on the wire going to post 86, then ground wire off 85 post to chassis. This activates the relay to click on or off. As most automotive switches can't handle being run inline on a seat heater setup. If it's hooked right, you should hear it click and can check continuity between 30/51 & 87 and multimeter should beep when switch is on and stop when switch is off.

Then you could twist the white/blue and white/red wires like you talked about above and connect them both to the 30/51 post and the 12 V White/Green power source to post 87.
No worries that the seat will burn out with the two wires getting 12V. The drawings show they both get 12V with the seat switch on High.
Hope that helps.

Thanks for the information! I tried hooking it up with the relay. I thought about the wires getting hot and increasing resistance so I went up to 12 gauge wire. I will try twisting white/red and white/blue together and see if it gets hotter that way