Stock Fan Relay And Wiring Questions To With Install Of Holley Efi

Discussion in '1994 - 1995 Specific Tech' started by moneypit94, Sep 19, 2013.


  1. moneypit94

    moneypit94 Active Member

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    I need to know what pins are positive and negative on the fan and which control the high and low speeds. Also What amp is the fan rated at?

    I am wiring up my holley efi system and I need to know what relay size or sizes I need. When the high side kicks on does it draw from the same power/relay as the low side or do I need to have two relays?
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  2. moneypit94

    moneypit94 Active Member

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    Ok.. The little I found with the search says there is a high side relay and a low side relay. Were where the stock relays for this located? Also if you have the low side on and then turn on the high side does the power to the low side need to be cut off? Im pretty sure either way I can setup the ECU to handle this. I am about 3 sensors, a few lose wires, and some setup on my laptop from starting up my car again. LONG TIME COMING after the PMCS kind of let me down along with two pistons.
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  3. toyman

    toyman SN Certified Technician

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    This thread from a week or so ago should give you most of what you are looking for.
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  4. HISSIN50

    HISSIN50 "How long does it take to get help in here? SN Certified Technician

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    If Richard's link doesn't open, try this: CLICKY

    Quick replies here: High and low should not be on at the same time (it causes the fan to run at slightly less than full speed but with a greater draw than high). If you can't accomplish shutting off low with the puter, you can do it mechanically with a relay.

    People will say you can use 40 amp SPDT relays but I would use a 75 amp HD Bosch/Tyco relay (for high speed at least).

    You need two relays (low and high).

    I would use separate fused battery supply wires (one for each relay).
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  5. moneypit94

    moneypit94 Active Member

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    Im sorry.. I meant to ask about the 3 pins/spades on the fan or wiring colors for high side +, low side +, and ground? I am assuming that's what they would be. I removed most of the old ECU and wiring. I still have all the harnesses and use the pigtail ends that I need.

    I found this randomly. So does the fan diagram match up? Is the ground in the middle? This is a nice diagram but I don't think I need a manual override switch though.

    [​IMG]
    Last edited: Sep 19, 2013
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  6. moneypit94

    moneypit94 Active Member

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    Where are the factory relays located? Is there a way of reusing them? The cheapest 75 amp relay is $26 from what I have found. They advertise 50 amp relays for cheap and I looked at autozone for a quick fix and was just going to use spade connectors on one of their relays. They were advertised in watts though and the biggest one was like 134 watts and 12.2 volts I think. That's only like 11 amps, so it made me kind of question the cheap 50a ones advertised.
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  7. HISSIN50

    HISSIN50 "How long does it take to get help in here? SN Certified Technician

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    The factory relays are inside the CCRM. You could continue using. You'd want to pair up the EDF and HEDF triggers to the ECU drivers (BE SURE THE POLARITIES ARE CORRECT).

    I can't remember what terminal is what on the fan motor but I seem to recall that the terminals are labeled.

    If you keep the CCRM intact and just use the new ECU to trigger it (CCRM Pins 14 and 17. AGAIN confirm polarity coming from the ECU, as Pin 14 needs to receive 12V and Pin 17 needs to see ground, and both should not be active at the same time), you should be able to leave the fan pigtail/connector alone.
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  8. moneypit94

    moneypit94 Active Member

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    I don't think I will be using the CCRM. I have cut out anything that wasn't used for like lights or the starter. Quick question. Just found they sell cheap 80 amp relays from china for dirt cheap. (as I was typing that I kind of smacked myself in the head for everyone.) That a bad idea to just buy a couple of those and try them out. 5$ a piece.
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  9. HISSIN50

    HISSIN50 "How long does it take to get help in here? SN Certified Technician

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    I'm a frugal guy, but for something like a fan I would use a brand name. That's just me.

    You could get a couple of the cheapies if you want to try them, but I'd still have a Tyco relay on hand (you could always sell it later, though it's great to have one around. You know you'll use it one day).

    Those Bosch/Tyco relays come in some Fords too (I'd have to google to figure out which), but if you're a J/Y hunter, that's another option.
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  10. ProKiller

    ProKiller Founding Member

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    wow, he's back! how's the beast coming along?
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  11. toyman

    toyman SN Certified Technician

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    The fan control outputs from the ECU are:
    Low fan pin 55
    High Fan pin 32
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  12. HISSIN50

    HISSIN50 "How long does it take to get help in here? SN Certified Technician

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    Great info!
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