Mark viii fan - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**pete63** · 05-07-2013, 07:15 AM

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 · 05-07-2013, 08:38 AM

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

**pete63** · 05-09-2013, 07:09 AM

Thanks for the reply..I talked to them yesterday prob the route I am going to go
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Custom 68 · 05-09-2013, 09:26 AM

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 · 05-09-2013, 09:41 PM

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.

05-07-2013, 07:15 AM	#1
pete63 Active Member Join Date: Aug 2007 Location: wisconsin Posts: 112	Mark viii fan 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 Posted via Mobile Device

05-07-2013, 08:38 AM	#2
Big Port Jimmy 6 Addicted to Rust Join Date: Dec 2009 Location: Abbeville SC Posts: 1,030	Re: Mark viii fan To be honest by the time I bought the relays and connectors, that Hollister Road set up isnt a bad deal. Jay __________________ Current trucks: (48 GMC100 320 inliner) Gone (48 Suburban in pieces) Sold 87 GMC CCSB 5.3 4l60E Daily Driver ECTA National record holder XO/PP We never really grow up, we just learn how to act in public.

05-09-2013, 07:09 AM	#3
pete63 Active Member Join Date: Aug 2007 Location: wisconsin Posts: 112	Re: Mark viii fan Thanks for the reply..I talked to them yesterday prob the route I am going to go Posted via Mobile Device

05-09-2013, 09:26 AM	#4
Custom 68 Registered User Join Date: Nov 2001 Location: Springfield, MO Posts: 2,939	Re: Mark viii fan 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 __________________ Dave 1968 Custom Chevy with turbo charged 5.3 gen III 4l80e swap 1967-71 GMC 3/4 ton long step 4x4 (not sure what year exactly?) "A good friend will bail you out of jail...but a true friend will be sitting next to you saying "that was frekin awesome". "If it doesn't fit force it...If it breaks then it needed to be replaced anyway!"

05-09-2013, 09:41 PM	#5
OKGMC4 Registered User Join Date: Oct 2009 Location: Broken Arrow, OK Posts: 1,245	Re: Mark viii fan 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. __________________ 56 GMC BUILD THREAD: http://67-72chevytrucks.com/vboard/s...d.php?t=368649 69 long bed Chevy turned 67 gmc jimmy roadster: https://67-72chevytrucks.com/vboard/...d.php?t=851167



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