cooling issues - baked relay - 2001 deville - 8 ft stretch limousine (factory built)
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1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, cooling issues - baked relay - 2001 deville - 8 ft stretch limousine (factory built) in Past Cadillac Vehicle Discussion; sorry that this post is lengthy, but i'm trying to answer all questions to someone in the know, before they ...
  1. #1
    crxted is offline Cadillac Owners Member
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    cooling issues - baked relay - 2001 deville - 8 ft stretch limousine (factory built)

    sorry that this post is lengthy, but i'm trying to answer all questions to someone in the know, before they have to ask them.

    here's what i've ascertained so far. there are two radiator cooling fans. one draws +/-2.5 amps of current under load, the other draws +/-8.5 amps. the 2nd one seems a bit excessive so i'm hoping that someone can verify if that's normal or not. the amount of heat generated inside the relay box in the right front corner of the engine compartment is enough to thaw and heat my lunch. i replaced all of the 3604 relays (the square ones) because they looked really tired (brown tint on the gray housings). one of the relay contacts (30/87?) of the higher amperage fan is bubbled on the plastic where the relay plugs into the board next to the other relays. as a result, i believe that relay is functioning intermittently thereby causing my overheating problems. what i would like to do is to bypass the OEM relays and extend the 10 ga. wiring to a couple of 30 amp Bosch relays that i would mount directly behind the r/h headlight where there is much less heat. i went to the boneyard and tore apart another deville to see exactly what i'm dealing with, and i grabbed several feet of the l.blue, white, and gray wiring to keep everything uniform. there is a black 10 ga. also that appears to go to a ground distribution. so one fan has a l.blue and the black which goes to ground. the other fan has a white and a gray, both 10 ga..

    here's where i'm stuck: on the fan with the white wire and gray wire - what is the current path of each wire? which is the negative, and is the negative switched as well as the positive for some reason? the diagram that i saw online was just a bit confusing. i'm hoping that an expert in this area can clarify this before i start my little project. thanks in advance.

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    JimD is offline Cadillac Owners Connoisseur
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    Re: cooling issues - baked relay - 2001 deville - 8 ft stretch limousine (factory bui

    First a fine print disclaimer. I have no idea if the engine cooling setup for a Limo chassis is different than a standard Deville 5 passenger chassis. Considering Limo service and the potential for extensive operation at engine idle with A/C and high current loads, there could easily be differences.

    Quote Originally Posted by crxted View Post
    ....here's what i've ascertained so far. there are two radiator cooling fans. one draws +/-2.5 amps of current under load, the other draws +/-8.5 amps. the 2nd one seems a bit excessive so i'm hoping that someone can verify if that's normal or not.
    An 8 or 9 amp continuous draw through a 30 amp fuse is not excessive. If there is a fan motor issue, I would suspect the motor that only draws 2 to 3 amps. But before leaping to conclusions, I would want to know if the fans were commanded to high speed or low speed when the current was measured.

    here's where i'm stuck: on the fan with the white wire and gray wire - what is the current path of each wire? which is the negative, and is the negative switched as well as the positive for some reason? the diagram that i saw online was just a bit confusing. i'm hoping that an expert in this area can clarify this before i start my little project. thanks in advance.
    The RH fan motor is the one that has the gray wire and the white wire. The white wire will eventually reach chassis ground, but not directly. The COOLING FAN S/P relay determines whether the RH fan motor is connected directly to chassis ground (high speed fan operation) or if the RH fan motor gets to chassis ground in series with the LH fan motor (low speed fan operation).

    Since you are in a relay buying mood, I would suggest you also replace the COOLING FAN S/P relay as a test. Be careful as that is a 5 pin relay and I do not know if aftermarket parts stores carry such a beast.

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    rodnok01's Avatar
    rodnok01 is online now Cadillac Owners Connoisseur
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    Not uncommon for corrosion to overheat those relays. I've found more than a few toast from bad connections.
    I get the five pin relays on ebay dirt cheap compared to loacl fyi.

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    Submariner409 is offline If it won't run, stick on fender vents
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    Re: cooling issues - baked relay - 2001 deville - 8 ft stretch limousine (factory bui

    2000 and later cooling fan circuit diagram in my albums.

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    crxted is offline Cadillac Owners Member
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    Re: cooling issues - baked relay - 2001 deville - 8 ft stretch limousine (factory bui

    sincere thanks for all of the helpful replies. after surveying the diagrams for the cooling fans, the series/parallel relay convinced me that i simply needed to replace the fuse/relay box. it's a much simpler operation than the bypass that i was planning to do. i hit several boneyards and found an exact replacement* fuse/relay box as the one in the limo. it cost me $50, but well worth every penny since the one got is in pristine condition - no baked terminals. i shudder to think what the dealer would've charged to get that piece over the parts counter. anyway, i will be installing it tomorrow morning. i expect that it will resolve my cooling fan issues, but i will come back here to confirm that tomorrow around this time. once again, thanks for the fast and helpful responses.

    *the deville appears to have a couple of different configurations of the same fuse/relay box. one of them is missing a mini fuse and two maxifuses. mine is the one with the extra fuses.

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    crxted is offline Cadillac Owners Member
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    Re: cooling issues - baked relay - 2001 deville - 8 ft stretch limousine (factory bui

    well, i swapped out the modular fuse/relay panel. it took a total of about 10 minutes, including swapping out the relays & fuses (yes, i replaced the questionable fan relay with a known good one). drove the limo for the better part of the day including some substantial "sit and wait" time. it appears to have held up well by the indication that the temp didn't climb at all. i pulled the fan relays after parking the car at the end of the day so that i could look for any potential burn marks developing. it all looks good. i'm hoping that it will stay that way.

    next issue... that notorious northstar engine and it's alleged propensity to leak oil and blow head gaskets. i guess that's for a separate thread.

  8. #7
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    Submariner409 is offline If it won't run, stick on fender vents
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    Re: cooling issues - baked relay - 2001 deville - 8 ft stretch limousine (factory bui

    Quote Originally Posted by crxted View Post
    next issue... that notorious northstar engine and it's alleged propensity to leak oil and blow head gaskets. i guess that's for a separate thread.
    "Alleged" is the operative word.

    Drive the car, perform all recommended maintenance at the recommended intervals - EXCEPT change/have changed the coolant at 3 year intervals - NOT that this exercise will prevent anything from failing - but block/head corrosion is the last thing you want in an aluminum engine.

    2001 car - Spend $450 at a Cadillac dealer for their "Fluids Exchange Special" - Coolant, P/S fluid, Transmission fluid (the new DEXRON-VI), brake fluid (the stuff LOVES moisture). If your battery is more than 5 years old it's living on borrowed time - especially in a limo.

    Go back into my albums and copy the pic of the annotated temp gauge - memorize the notes.

  9. #8
    JimD is offline Cadillac Owners Connoisseur
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    Re: cooling issues - baked relay - 2001 deville - 8 ft stretch limousine (factory bui

    Quote Originally Posted by crxted View Post
    well, i swapped out the modular fuse/relay panel. it took a total of about 10 minutes, including swapping out the relays & fuses (yes, i replaced the questionable fan relay with a known good one). drove the limo for the better part of the day including some substantial "sit and wait" time. it appears to have held up well by the indication that the temp didn't climb at all. i pulled the fan relays after parking the car at the end of the day so that i could look for any potential burn marks developing. it all looks good. i'm hoping that it will stay that way.
    You killed a entire species of birds with that stone. And I do understand that vehicle must be 'in service' to produce any revenue and excessive 'downtime' is not a profitable situation.

    It would be an interesting academic exercise to inspect the original fuse panel for corrosion/oxidation in addition to testing the original COOLFAN S/P relay.

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