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Thread: Heater blows cold

  1. #1
    Supporting Member II Turbo Mopar Contributor
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    Heater blows cold

    Hey guys, just wanted to bounce this off the members here before I go about draining my coolant and tearing into things.

    When I parked my car 5 years ago the heater worked. I rebuilt it finally, but now my heater does not work.

    When the car was waiting for the short block to be finished, I flushed out the heater core with CLR, and everything seemed fine there.

    I've verified that the blend door is moving from side to side when moving the cable controls.

    Below is an image of how I have my heater bypass valve routed...I'm pretty sure this is correct.

    Click image for larger version. 

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    I've also verified that the valve isn't seeing vacuum and bypassing the heater core itself.

    Both of my heater hoses remain cold.

    At this point I don't know what to do except drain it, replace the bypass valve for good measure, and triple check that the heater core and associated hoses are all free of blockage and can flow freely.

    -Zach
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  2. #2
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    Re: Heater blows cold

    if you need heat ,now ,simply delete the valve using some tubing to join the hoses

    I think later cars maybe 90's + don't have it anyways

    the blend door may prove sufficient ..at least until mid summer (?)

  3. #3
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    Re: Heater blows cold

    You could also bypass the bypass valve.

  4. #4
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    Re: Heater blows cold

    Quote Originally Posted by Dr. Johny Dodge View Post
    if you need heat ,now ,simply delete the valve using some tubing to join the hoses

    I think later cars maybe 90's + don't have it anyways

    the blend door may prove sufficient ..at least until mid summer (?)
    Agreed. Not only did they do away with it on latr cars, but I doubt it would be noticed in OR anyway.

  5. #5
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    Re: Heater blows cold

    Tempting to just remove it altogether, hmm..either way I'll have to drain the coolant and get in there. If the problem is apparent when I do, I may just pop in my spare. Never had a problem with the system before..but, I do know some squirrels got into the engine bay when the car was sitting. They stuffed acorns in my turbo and heater hoses..they might have shoved some ---- in that valve too lol
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  6. #6
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    Re: Heater blows cold

    The bypass valves are prone to leaks, esp. aftermarket ones. That is main reason for eliminating them. I have removed mine from several cars with working AC. All work great without it. Not much of a risk.
    Heater hoses should not be cold regardless. Something obviously isn't right, as even a stuck open thermostat will eventually result in warm but not hot heat. You should probably check every hose in the entire system for blockage. Is the car running cold/hot on gauge? Is the car reaching full operational temperature? Do you have infrared temp sensor to check head/radiator temps? If not, pretty useful tool for checking all sorts of things. They have come way down in price.
    Todd

  7. #7
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    Re: Heater blows cold

    Hi Todd,

    I have an aftermarket temp gauge and the stocker hooked up. Engine temps are reading just fine, with normal ranges and proper fan scheduling. Haven't checked with an infrared, but I have a middling quality one from Amazon I can play with next time I take it for a drive.

    Honestly I'm expecting some sort of physical blockage, the rodents had a lot of fun with this car when it was sitting. Here's what I dug out of my cowl when prepping to drop in the engine🙄
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  8. #8
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    Re: Heater blows cold

    potential blockage .. if unused for a length of time the little pivot shaft in the valve is likely rusted stuck in the plastic..

    or the diagram is wasted..
    or you have vacuum leak in the line somewhere

    have you at least tried to move the little link below the diafram on the valve?
    start ..there

  9. #9
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    Re: Heater blows cold

    Yup, I did. The spring does it's job and the valve isn't seeing vacuum when it shouldn't. The valve itself appears to be okay.
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    Re: Heater blows cold

    if you have a few pairs of locking pliers and some cardboard you don't need to drain much to remove the valve .. simply , gently clamp off the heater hoses using the cardboard wrapped around the hoses to protect them

    cereal box or such will do and an old towel under the work area will take care of any minor spillage

    a spill tray could be easily made cutting up a washer fluid jug to pour the little bit of coolest in the hose ends out..if you don't have room to simply stick the hose end in the jug opening

  11. #11
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    Re: Heater blows cold

    nice suggestion Johny
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  12. #12
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    Re: Heater blows cold

    thanks..
    some dollar store C clamps would do the trick , probably better with regard to space

  13. #13
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    Re: Heater blows cold

    Just as an update. Found the problem. Was the fecking squirrels like I suspected!

    Dang acorn was in the return line to the water pump. So, the water in the heater system just had nowhere to go. No flow, no heat.

    Problem solved. I ended up deleting the bypass valve, and I don't think my heater has ever worked as well lol
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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Heater blows cold

    So, someone or something dropped an acorn down in the raf? Thatís a rare one!

  15. #15
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    Re: Heater blows cold

    The car seat for quite a while all torn apart, the rodents had some fun. I thought I had caught everything, acorns in the turbo, IC, and charge piping. Acorns in some radiator hoses. Nest in the cowl. They chewed through the lower IC hose so I had to source another one of those 🙄

    But I guess I missed one last surprise. They haaad to stuff another 'present' in that lower water pump hose.
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  16. #16
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    Re: Heater blows cold

    Well glad you found it Zach. One by one, all those bugs are getting worked out! Yes those squirrels once got into the interior of one of my l-bodies. They decided the top of my radio was a good place the pee and defecate. In the spring, found radio had shorted out. Tore the whole car apart looking for their nest. Of course started at the front of vehicle, found the nest in the carpet insulation between the taillights. That took a while...Another time the distance sensor wiring was apparently used as dental floss. That could have been squirrels too I guess.
    Todd

  17. #17
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    Re: Heater blows cold

    Quote Originally Posted by 4 l-bodies View Post
    Well glad you found it Zach. One by one, all those bugs are getting worked out! Yes those squirrels once got into the interior of one of my l-bodies. They decided the top of my radio was a good place the pee and defecate. In the spring, found radio had shorted out. Tore the whole car apart looking for their nest. Of course started at the front of vehicle, found the nest in the carpet insulation between the taillights. That took a while...Another time the distance sensor wiring was apparently used as dental floss. That could have been squirrels too I guess.
    Todd
    Thanks Todd. Yup! I'm determined to restore old Jango to his former glory. While I've had the car for 15 years, it's been down for about the last 5. But before that I took it everywhere for 10 years without any major issues. Still chasing down that misfire condition, but that's the last high priority item for me.

    This has been my first encounter with rodents making a home out of my car - certainly frustrating, but I think I got off somewhat easy compared to you. At least my best was pretty obvious. It's the piss that's the worst. Can't imagine what radio electronics shorting in it must have been like 😬

    Just today when I was fixing the heater I figured I'd fix the driver corner light on the fender cause it was burnt out since I got the Lancer running again. Popped it out and the whole pigtail just came with it. Looks like rodents chewed through the wires right where they travel through a port in the sheet metal, tucked behind the SMEC, battery, and overflow tank. I can probably solder it, but not without taking all that out..

    I ended up just popping the thing back in it's socket and dusting my hands. That's a project for another time lol
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