Mark viii fan

[pete63]

I did a search but couldn't seem to find exact answers. I have a 2002 5.3 and will be using mark viii elec fan. Wondering if anyone has info on wiring this into PCM? I know I will need larger relays for the power draw, but wondering if someone had a drawing how they did theirs. Also has anyone used this companies setup, is it worth the $ to go this route?
http://www.hollisterroad.com/proddet...?prod=MarkVIII
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[Big Port Jimmy 6]

To be honest by the time I bought the relays and connectors, that Hollister Road set up isnt a bad deal. Jay

[pete63]

Thanks for the reply..I talked to them yesterday prob the route I am going to go
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[Custom 68]

ok I will try not to make this too confusing... lol
The computer of course controls the fan off and on and some will even control 2 fans. Mine is a 5.3 and I only have one hooked up. I dont have the diagram for the harness but it can be found, the wire for the fan go to GROUND when the computer tells it to come on. What that means is that your relay must be setup to trigger on when it is grounded. I dont remember the schematic but I do remember there must be 2 hot wires going to the relay. The wire coming from the relay to the fan will still be the hot wire.
It is not too bad but you just have to remember the relay will be hooked up different than what the normal (on the box) method. I believe most of those require a hot wire for the switching rather than the ground. This is not a special relay just any 30 amp should work.
hope that helps.
Dave

[OKGMC4]

I don't know how to do it with the ecm, but I did mine with a volvo two speed relay and a BMW two speed fan switch. I explained how I did it on my 5.3 here...

http://67-72chevytrucks.com/vboard/s...=368649&page=7

...with pics and wiring diagram, post 162 and 165. Thing works great, and in 3500 miles, some of it in stop and go traffic, some over 100 degree weather, and with the A/C on I still havn't had the high speed kick on yet.