project88mj Posted November 4, 2008 Share Posted November 4, 2008 so if you can't understand me or the video does not work here is the problem as i have the heater on at all high or low. if i drive up a hill the heater cuts out almost compleatly and no air will blow :???: but... as i crest the hill and go back down the heater will blast back on hot as it ever was before :huh???: the size of the hill doesnt matter at all if there is any change of grade up the heater cuts out then comes back on when i level out or go back down :doh: never heard of the before have you? :dunno: :hmm: Link to comment Share on other sites More sharing options...
mvusse Posted November 4, 2008 Share Posted November 4, 2008 Gotta be a broken or loose wire or connection somewhere. Up hill it moves away, level or downhill it makes contact. Link to comment Share on other sites More sharing options...
mvusse Posted November 4, 2008 Share Posted November 4, 2008 Gotta be a broken or loose wire or connection somewhere. Up hill it moves away, level or downhill it makes contact. Link to comment Share on other sites More sharing options...
project88mj Posted November 4, 2008 Author Share Posted November 4, 2008 did the video work? Link to comment Share on other sites More sharing options...
project88mj Posted November 4, 2008 Author Share Posted November 4, 2008 did the video work? Link to comment Share on other sites More sharing options...
mvusse Posted November 4, 2008 Share Posted November 4, 2008 Yes it did. Link to comment Share on other sites More sharing options...
mvusse Posted November 4, 2008 Share Posted November 4, 2008 Yes it did. Link to comment Share on other sites More sharing options...
summerinmaine Posted November 4, 2008 Share Posted November 4, 2008 Sounds like the heater operation is responding to engine vacuum. Isn't the switch vacuum controlled? Link to comment Share on other sites More sharing options...
summerinmaine Posted November 4, 2008 Share Posted November 4, 2008 Sounds like the heater operation is responding to engine vacuum. Isn't the switch vacuum controlled? Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 4, 2008 Share Posted November 4, 2008 Look on the right front bulkhead near the firewall near the battery where the vacuum hose passes through to the cannister behind the front bumper. The vacuum hose has probably split or has a hole in it - very common problem. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 4, 2008 Share Posted November 4, 2008 Look on the right front bulkhead near the firewall near the battery where the vacuum hose passes through to the cannister behind the front bumper. The vacuum hose has probably split or has a hole in it - very common problem. Link to comment Share on other sites More sharing options...
aemsee Posted November 5, 2008 Share Posted November 5, 2008 It is probably switching to defrost when you lose vacuum to the control head. Next time you go up a hill see if it is coming out the defrost vents. Link to comment Share on other sites More sharing options...
aemsee Posted November 5, 2008 Share Posted November 5, 2008 It is probably switching to defrost when you lose vacuum to the control head. Next time you go up a hill see if it is coming out the defrost vents. Link to comment Share on other sites More sharing options...
Eagle Posted November 5, 2008 Share Posted November 5, 2008 It is probably switching to defrost when you lose vacuum to the control head. Next time you go up a hill see if it is coming out the defrost vents. ^^^ Agreed. The heater isn't "cutting out." It's "redirecting." The flappers that control air flow are operated by vacuum. One of the functions of the vacuum canister (the "football" or the "blimp") behind the right corner of the front bumper is to maintain vacuum when the engine is under load, such as going uphill, so the ventilation controls operate normally. The default position for the vants in the dashboard is the top-of-dash defrost outlets, so when you lose vacuum the air flow switches to those. When the vacuum comes back, the airflow reverts to wherever you had it set for. Either your vacuum reservoir is cracked (or missing), or you have a vacuum leak. Link to comment Share on other sites More sharing options...
Eagle Posted November 5, 2008 Share Posted November 5, 2008 It is probably switching to defrost when you lose vacuum to the control head. Next time you go up a hill see if it is coming out the defrost vents. ^^^ Agreed. The heater isn't "cutting out." It's "redirecting." The flappers that control air flow are operated by vacuum. One of the functions of the vacuum canister (the "football" or the "blimp") behind the right corner of the front bumper is to maintain vacuum when the engine is under load, such as going uphill, so the ventilation controls operate normally. The default position for the vants in the dashboard is the top-of-dash defrost outlets, so when you lose vacuum the air flow switches to those. When the vacuum comes back, the airflow reverts to wherever you had it set for. Either your vacuum reservoir is cracked (or missing), or you have a vacuum leak. Link to comment Share on other sites More sharing options...
BLHTAZ Posted November 5, 2008 Share Posted November 5, 2008 Yeah...it sounds like there is a loss of vacuum and the vacuum controlled door inside is closing and opening based on the angle of the vehicle. There seems to be enough vacuum there to hold it while level, but it's not strong enough to support it when you point the nose up :cheers: Link to comment Share on other sites More sharing options...
BLHTAZ Posted November 5, 2008 Share Posted November 5, 2008 Yeah...it sounds like there is a loss of vacuum and the vacuum controlled door inside is closing and opening based on the angle of the vehicle. There seems to be enough vacuum there to hold it while level, but it's not strong enough to support it when you point the nose up :cheers: Link to comment Share on other sites More sharing options...
mvusse Posted November 5, 2008 Share Posted November 5, 2008 My bad. I thought he meant the FAN for the heater was cutting out. Link to comment Share on other sites More sharing options...
mvusse Posted November 5, 2008 Share Posted November 5, 2008 My bad. I thought he meant the FAN for the heater was cutting out. Link to comment Share on other sites More sharing options...
FxRacing282 Posted November 5, 2008 Share Posted November 5, 2008 I thought he meant the FAN for the heater was cutting out. same. sounds like all the guys on here got it nailed. but i not going to agree with them. i think that someone is playing a joke on you and has rigged a system in your truck so that this would happen on purpose. maybe they think you wouldn't notice or wouldn't do anything about it. i say that you find their car and take the schraider valve out of their tire. Link to comment Share on other sites More sharing options...
FxRacing282 Posted November 5, 2008 Share Posted November 5, 2008 I thought he meant the FAN for the heater was cutting out. same. sounds like all the guys on here got it nailed. but i not going to agree with them. i think that someone is playing a joke on you and has rigged a system in your truck so that this would happen on purpose. maybe they think you wouldn't notice or wouldn't do anything about it. i say that you find their car and take the schraider valve out of their tire. Link to comment Share on other sites More sharing options...
Eagle Posted November 5, 2008 Share Posted November 5, 2008 My bad. I thought he meant the FAN for the heater was cutting out. It feels like that, if you don't know what's happening. It happened in my '88 XJ about ten years ago. Naturally, it was the coldest part of the winter. I'd be motoring along with the heat on high and the fan on to keep my feet nice and toasty, get to a long upgrade -- and all of a sudden my feet were freezing. Of course, it feels much worse than it is when you've been in a nice warm breeze and all of a sudden -- no more warm air. It's still blowing, but it's pushing the air up to the windshield, and you don't really notice or feel it there when your feet suddenly start icing up. First thing to check is the vacuum tubes in the vicinity of where they run past the battery tray. Link to comment Share on other sites More sharing options...
Eagle Posted November 5, 2008 Share Posted November 5, 2008 My bad. I thought he meant the FAN for the heater was cutting out. It feels like that, if you don't know what's happening. It happened in my '88 XJ about ten years ago. Naturally, it was the coldest part of the winter. I'd be motoring along with the heat on high and the fan on to keep my feet nice and toasty, get to a long upgrade -- and all of a sudden my feet were freezing. Of course, it feels much worse than it is when you've been in a nice warm breeze and all of a sudden -- no more warm air. It's still blowing, but it's pushing the air up to the windshield, and you don't really notice or feel it there when your feet suddenly start icing up. First thing to check is the vacuum tubes in the vicinity of where they run past the battery tray. Link to comment Share on other sites More sharing options...
project88mj Posted November 5, 2008 Author Share Posted November 5, 2008 :needpics: i looked and saw a bunch down there can i get some visual help here I thought he meant the FAN for the heater was cutting out. same. sounds like all the guys on here got it nailed. but i not going to agree with them. i think that someone is playing a joke on you and has rigged a system in your truck so that this would happen on purpose. maybe they think you wouldn't notice or wouldn't do anything about it. i say that you find their car and take the schraider valve out of their tire. hold on a second can you say rash deisison :nuts: Link to comment Share on other sites More sharing options...
project88mj Posted November 5, 2008 Author Share Posted November 5, 2008 :needpics: i looked and saw a bunch down there can i get some visual help here I thought he meant the FAN for the heater was cutting out. same. sounds like all the guys on here got it nailed. but i not going to agree with them. i think that someone is playing a joke on you and has rigged a system in your truck so that this would happen on purpose. maybe they think you wouldn't notice or wouldn't do anything about it. i say that you find their car and take the schraider valve out of their tire. hold on a second can you say rash deisison :nuts: Link to comment Share on other sites More sharing options...
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