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  1. #1

    Default why doesn't my front defroster work?

    Does my A/C need to be charged in order for the front windshield defroster to work? I can have the defroster cranked up to the max, with the lever on cool or warm and it'll blow for 10 + minutes and still not do a **** thing. Does anyone have this problem? How can I fix this? I hate having to drive with my head sticking out the window.
    Corey
    1965 Mustang
    1986 Mustang GT T-Tops - Explorer engine swap, MAF Conversion, 5 lug Cobra Brakes
    2001 True Blue Bullitt
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  2. #2

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    do you mean nothing happens as in it doesn't blow hot air, or doesn't blow at all or what?

  3. #3
    FEP Super Member MurPHy's Avatar
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    Default

    Sounds like a shot heater core. Do you smell antifreeze when it's running? I had the same problem awhile back.

  4. #4

    Default

    Sounds like your heater core isn't getting hot. Is it blocked in the lines somewhere?

    Do you feel air coming through the vents?

    -Mike

  5. #5

    Default

    oh yeah, which car? i see an 88 and an 86 in your sig. i know on my 79(w/ ac, not charged) i have a vaccum line coming out of the firewall that must be hooked up or i don't have any control over where it blows the air(floor vents or defrost).

  6. #6

    Default

    it's for the 86. It blows air alright. It blows really well. It's just the air that blows out doesn't do jack to clear the window up. I don't understand it. After a loooong time finally the window starts to clear up around the general area where the air is blowing but the window never clears up all the way. The heater core is less then a year old.
    Corey
    1965 Mustang
    1986 Mustang GT T-Tops - Explorer engine swap, MAF Conversion, 5 lug Cobra Brakes
    2001 True Blue Bullitt
    www.thompsontransmission.com - coming soon
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  7. #7

    Default

    Quote Originally Posted by negusm
    Sounds like your heater core isn't getting hot. Is it blocked in the lines somewhere?

    Do you feel air coming through the vents?

    -Mike
    The heater works great in the car, I don't think anything is blocking any lines, but then my car gets really hot when I sit in traffic and this is with a fluidyne radiator, new hoses, new heatercore, new thermostat, water pump is good. It's possible the coolant passages could be clogged maybe. I dunno. The heater does blow hot air though and I do feel air coming through the vents.
    Corey
    1965 Mustang
    1986 Mustang GT T-Tops - Explorer engine swap, MAF Conversion, 5 lug Cobra Brakes
    2001 True Blue Bullitt
    www.thompsontransmission.com - coming soon
    Fox Body Black Interior Interchangeability Guide

  8. #8
    FEP Supporter Zap's 85 GT's Avatar
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    Default

    The vent system is primarily switched by vacuum. Maybe one of the lines has become disconnected or the defroster door/cylinder is stuck.

    Does your car switch between FLOOR and VENT and MIX properly? If not maybe your primary vacuum line going to the HVAC control isnt hooked up. There should be a line for that in the engine compartment that goes from the main vacuum tree into the firewall.
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  9. #9

    Default

    Quote Originally Posted by Zap's 85 GT
    Does your car switch between FLOOR and VENT and MIX properly?
    I'll check in a little bit when I leave for work.
    Corey
    1965 Mustang
    1986 Mustang GT T-Tops - Explorer engine swap, MAF Conversion, 5 lug Cobra Brakes
    2001 True Blue Bullitt
    www.thompsontransmission.com - coming soon
    Fox Body Black Interior Interchangeability Guide

  10. #10

    Default

    Quote Originally Posted by Zap's 85 GT
    The vent system is primarily switched by vacuum. Maybe one of the lines has become disconnected or the defroster door/cylinder is stuck.

    Does your car switch between FLOOR and VENT and MIX properly? If not maybe your primary vacuum line going to the HVAC control isnt hooked up. There should be a line for that in the engine compartment that goes from the main vacuum tree into the firewall.
    This is what happens..
    When Mix is on, only the defroster and floor vents have air coming out through them. The vents facing me are dead. When I put the hvac controls onto floor or defroster, air blows through just fine. When I put the controls on vent, things blow through just fine too. So I don't know. Air blows through the defroster vents but the window just doesn't defrost, very frustrating. Could this be a result of the A/C system needing to be recharged?
    Corey
    1965 Mustang
    1986 Mustang GT T-Tops - Explorer engine swap, MAF Conversion, 5 lug Cobra Brakes
    2001 True Blue Bullitt
    www.thompsontransmission.com - coming soon
    Fox Body Black Interior Interchangeability Guide

  11. #11

    Default

    So you get a good SOLID stream of HOT air going past your windshield?

    If so, then you have a MAGIC windshield! Call Ripley's!

    What are the temperatures there? in so cal? It can take 10 minutes (under load) for a car to warm up and get the heater core hot enough to defrost the windshield....more time if you just let the car idle with no load.

    Once the air coming out of the defroster is HOT, it should take 3-5 minutes to defrost the windshield.

    Your AC system should have no effect on the heater. My AC was discharged for the longest time and the heater worked.


    -Mike

  12. #12

    Default

    yea i can feel a good stream of air going across the windshield. The defroster in my friends civic works off of the A/C and clears the whole windshield in probably not more then 30 seconds. Damn new cars.
    After the engine has warmed up, the defroster will defrost but it just takes forever and a day to do it.
    it just sucks though because in the morning I can't see jack out the front windshield. I can't sit there and wait for the defroster to clear the window, i'll be late to work if I do that. I can't drive the car to put load on the engine to get things heated up because I can't even see out of the windshield. oh well. Maybe I should just stop my complaining and deal with it
    Corey
    1965 Mustang
    1986 Mustang GT T-Tops - Explorer engine swap, MAF Conversion, 5 lug Cobra Brakes
    2001 True Blue Bullitt
    www.thompsontransmission.com - coming soon
    Fox Body Black Interior Interchangeability Guide

  13. #13
    FEP Member
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    Default

    The Defrost setting works in conjunction with the A/C compressor. The A/C system will dehumidify the air prior to send it thru the Heater core and up to the windsheild.

    Your defroster would work better if your A/C was also working.

    Steve
    1983 Mustang GT

  14. #14

    Default

    the previous owner of my 85 had the AC updated to the newer charge and damn.. all I can say is that windshield defrosts very quick compared to the other FOXes I've had. The other FOXes I've had... the AC either didn't work or KINDA worked. But even the ones that didn;t work the defroster still did it's job... alot slower though.
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  15. #15

    Default

    hmm, i guess I should get the A/C fixed then. Does anyone know whats involved with converting to the newer type of A/C and how much it costs? Maybe I should put up a new thread...
    Corey
    1965 Mustang
    1986 Mustang GT T-Tops - Explorer engine swap, MAF Conversion, 5 lug Cobra Brakes
    2001 True Blue Bullitt
    www.thompsontransmission.com - coming soon
    Fox Body Black Interior Interchangeability Guide

  16. #16

    Default

    Quote Originally Posted by 50 Proof
    The heater core is less then a year old.
    Bad heater core.

    Did you put a cheapy aftermarket one in?

    Have you even touched those hoses since you put the heater core in? Are your motor mounts original?

    Seems like even a slight breeze will crack a tube in one of those piece of crap aftermarket cores.

    Get a Ford core. 45 bucks or so, but the tubes are braced. Also get new hoses and spray/soak the hoses in WD 45 before slipping them on.
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  17. #17
    FEP Member
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    Default

    I can give you some advice on the a/c conversion. I've done two of them. One the expensive way and one the cheap way. But why don't you start a new thread and I'll post to it.

    Steve
    1983 Mustang GT

  18. #18

    Default

    Quote Originally Posted by GT350R
    Quote Originally Posted by 50 Proof
    The heater core is less then a year old.
    Bad heater core.

    Did you put a cheapy aftermarket one in?

    Have you even touched those hoses since you put the heater core in? Are your motor mounts original?

    Seems like even a slight breeze will crack a tube in one of those piece of crap aftermarket cores.

    Get a Ford core. 45 bucks or so, but the tubes are braced. Also get new hoses and spray/soak the hoses in WD 45 before slipping them on.
    it's a ford heater core, the motor mounts are bad, they have 187k miles on them. I haven't touched those hoses or tubes since installing the heater core. I don't get that film on the window when a heater core is bad, and hot air blows great through the vents. Otherwise, how else can you tell that the heater core is bad?
    Corey
    1965 Mustang
    1986 Mustang GT T-Tops - Explorer engine swap, MAF Conversion, 5 lug Cobra Brakes
    2001 True Blue Bullitt
    www.thompsontransmission.com - coming soon
    Fox Body Black Interior Interchangeability Guide

  19. #19

    Default

    Is this in the comvertible?

    If so, start looking for leaks. I have seen this on cars with trunk leaks or wet carpet.
    The sheep lie!
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    84 Turbo GT 11.70@120MPH 418RWHP
    89 LX Vert 5.0 twin turbo , 90 GT triple back vert, 91 Gt vert 347, 89 Coupe 2200 miles, 93 Coupe , 87 Gt , 91 Gt

  20. #20

    Default

    it's in my 86 T-Tops, no leaks so far, carpet is dry.
    Corey
    1965 Mustang
    1986 Mustang GT T-Tops - Explorer engine swap, MAF Conversion, 5 lug Cobra Brakes
    2001 True Blue Bullitt
    www.thompsontransmission.com - coming soon
    Fox Body Black Interior Interchangeability Guide

  21. #21
    FEP Power Member LTDScott's Avatar
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    Default

    The defroster relies on the A/C compressor to de-fog the windows. Apart from making the air cold, part of the A/C's job is to remove moisture from the air. So if you flip your controls to "Defrost," the air should come out of the dash vents and the A/C compressor should kick in.

    So if your A/C isn't working, the moisture isn't being removed from the air and the regular "non-conditioned" air blowing on the windshield won't help much. Does your normal A/C work?

    On my Mazda, I have to turn the A/C on manually (has a separate switch) even if the defroster is on. If I don't turn the A/C on, it'll take forever to clear the window. I don't think the heater core has anything to do with your problem, unless it's leaking and CAUSING the windows to fog up.
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  22. #22

    Default

    Several times in this thread I've seen Corey say "defrost". So are we talking about "frost" on the windshield that's not clearing up or "fog" that's not clearing up?
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  23. #23

    Default

    Are we talking de-fog or de-frost?

    More of a concern to me is the frost on the outside of the car...which won't be affected one bit by the moisture in the air coming out of the heater...

    -Mike

  24. #24

    Default

    Quote Originally Posted by FoxChassis
    Several times in this thread I've seen Corey say "defrost". So are we talking about "frost" on the windshield that's not clearing up or "fog" that's not clearing up?
    sorry, i guess I mean defog. I can take my hand and wipe the inside of the window clear kind of(it gets fogged up again). The windows are not fogged up because of a bad heater core. Frost on the outside of the windows doesn't happen very often in california.
    Corey
    1965 Mustang
    1986 Mustang GT T-Tops - Explorer engine swap, MAF Conversion, 5 lug Cobra Brakes
    2001 True Blue Bullitt
    www.thompsontransmission.com - coming soon
    Fox Body Black Interior Interchangeability Guide

  25. #25
    FEP Power Member LTDScott's Avatar
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    Default

    LOL, maybe this is a regional difference. I believe 50Proof lives in Corona, CA, where it's probably 80 degrees today, and actual frost is not something he usually has to deal with. So more than likely he needs to "de-fog" the inside of the windshield, something that we have to deal with frequently.

    Or maybe I'm making incorrect assumptions!
    85 Ford LTD LX: Four eyes and Four doors

    EFI swap, AFR 165 heads, 5-speed conversion, Cobra brakes, etc.

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