why doesnt my heater work?

how much is vacume involved in making my heater blower turn on? it works intermitinly, mostly just doesnt work when its cold. is it just a loose connection behind the dash? it still gets hot and some air will slowly leak out when i have the heater on buy no blower. am i being clear? it hasnt been over 35 out here in weeks, save me!

Build a campfire in the passenger seat. :flame:

Give us some info on the Heep...year for starters

1987 4.0 AW4 "tow package" (really.) stripper, has a heater, full gauges. (not idiot lights) thats about it, no ac, i put a stereo in it so there has been some messing around behind the dash. it started around the same time as i tried that stupid zip tie shift mod, and i put on 30x9.5's. all at the same time abouts. the heater has always done the thing where when the engine is working hard AT HIGHWAY SPEEDS ONLY the heater will switch from vent to defrost until i let up off the gas a little.

3.55 gears, no power anything, 196k miles

The blower motor itself is completely electric. Only the HVAC settings (Defrost, Vent, Heat) are controlled by vacuum. Sounds like your blower motor is dead.

You need to check the vacuum bottle. I had some leaks in the vacuum hoses going to it and it made the heater not work because the vacuum switch that controls the coolant flow into the heater core wasn't opening.

Another thing you can do that's pretty easy and really helped out the heat on my rig was to flush the heater core. I just got a little barbed fitting from the hardware store that screwed onto the end of my garden hose and fit into the disconnected heater hoses. Flush against the normal coolant flow first, you'll probably get a bunch of junk coming out first, then let up when it starts running clear, then go to the other one and flush that way, back and forth a bit. My heater hardly put out any heat at all until I did this, and now it will suffocate you with heat if you leave it on full blast.

mine did the same thing yours does. If I smacked the dashboard occasionally it would function again. Pull the dash trim, and then pul the HVAC controls. Make sure you tag all the different things back there before you unplug them. Mine was the connection at the switch. The motor had 12V, but without the switch there isn't a ground. You can test the blower motor by running 12v directly to it and grounding the ground. I just used some 18Ga wire I had lieing around. Don't run it on this wire for long, it's really not heavy enough to supply the kind of current you need. It was handy to verify that I had a wireing problem and not a dead blower motor though.
Good luck.

yeah, blower has worked since yesterday afternoon, therefore its not dead, just a wiring problem. but i think that there is a vacume leak somewhere, when the engine is working hard and the heat switches to defost, its not even warm air. does flushing the heater core help with engine heat too? my buddy Hutt just did his turbo mini van and i think he said it helped with coolant temps too. more flow maybe? tee hee turbo mini van, Hutt is gonna buy a new top end kit for one grand that will solidly put him in the 13's in the quarter. i want to run that in my heep for 1000 worth of mods! (well he will need a new clutch and slicks too)

Check those vacuum lines going under the battery like "NotMatt" was saying. Without that canister working right, the doors will be very intermitent and will shift on you when you change the motor speed. I have to backflush mine also cause I procrastinated about doing this past year. This is not good to do as it sometimes starts leaking afterwards. Wrong time of the year to pull the dash down. Ah well. . .

Grizzley said:

Check those vacuum lines going under the battery like "NotMatt" was saying. Without that canister working right, the doors will be very intermitent and will shift on you when you change the motor speed. I have to backflush mine also cause I procrastinated about doing this past year. This is not good to do as it sometimes starts leaking afterwards. Wrong time of the year to pull the dash down. Ah well. . .

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marshall...what do you mean ? With the wind chill its 19 degrees.

so I've got my dash apart to fix this properly. Before I just wiggled the connector. If anyone wants pics let me know. Mine was the big connector at the upper passenger side of the HVAC controller. THe connector plugs into an edge style connector, the contaces on mine were intermittent. I cleaned the contacts with cleaner, and bent the contacts back into the center. The blower works much better than it ever did now. I've also creamed it with di-electric grease.

87manche said:

so I've got my dash apart to fix this properly. Before I just wiggled the connector. If anyone wants pics let me know. Mine was the big connector at the upper passenger side of the HVAC controller. THe connector plugs into an edge style connector, the contaces on mine were intermittent. I cleaned the contacts with cleaner, and bent the contacts back into the center. The blower works much better than it ever did now. I've also creamed it with di-electric grease.

Click to expand...

mmmmmn......grease.

so yeah, blower was dead, still have to order one from napa, or get one online?
anybody done this, where and with what results? ive looked and there seems to be about 8 Different part numbers, all listed years run 88-96, except for one says fits 84-94. i have not ran the p/n off of my old one yet.