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what to do? 89 swb 4.0l

 

Normally the sign of a bad resistor pack is that is only works on high. But it can in some instances quit working all together. I assume you have checked for a blown fuse. It can also be a bad blower moter speed switch.

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If the fan is blowing, but no heat then either your heater core is plugged up or your heater control valve is not working.

 

If the fan is not working, then it could be a fuse, the fan switch, the blower motor or the blower motor resistor has gone bad.

 

If the blower is not working, I would start with finding out why and getting that going first. If you have no heat after that, then you will need to determine if your heater control valve is working or if the core is plugged.

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Pete said this in the other heater thread:

 

Yup. Check your lines and check the vacuum ball in the front bumper for cracks.

 

Lets just say that I cut my bumper real short in the front and instead of screwing this "ball" down I kinda let it dangle, then lets also say that one time when I was tooling around that my passanger front LTB was able to grab this ball and launch it very far away from the truck.... The lets also say I forgot where I put said "ball" and have just been driving around with out this "ball" ever since.... We could additionally gander that MAYBE I did have heat before the "ball" earned its wings.

 

What does the ball do exactly?

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Pete said this in the other heater thread:

 

Yup. Check your lines and check the vacuum ball in the front bumper for cracks.

 

Lets just say that I cut my bumper real short in the front and instead of screwing this "ball" down I kinda let it dangle, then lets also say that one time when I was tooling around that my passanger front LTB was able to grab this ball and launch it very far away from the truck.... The lets also say I forgot where I put said "ball" and have just been driving around with out this "ball" ever since.... We could additionally gander that MAYBE I did have heat before the "ball" earned its wings.

 

What does the ball do exactly?

 

It collects negative(vacuum) pressure and stores it for things like heater controls,,, and axle disconnects,,, and on s-10 4wd's CAD too!!

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What does the ball do exactly?

The ball (a.k.a. "the blimp") is a vacuum storage reservoir. The heater controls are all actuated by vacuum. That's what moves the flappers that direct air to your feet, the front of the dashboard, or the top of the dashboard. The default (if you have no vacuum) is the defrost outlets on top of the dash.

 

What the blimp does is provide a small reservoir to hold vacuum when the engine is under heavy load, such as going up a long incline. When the hose to mine started leaking, I had normal heat on my feet on level ground, then going up long hills the output would gradually shift to the defrost. Once I topped the hill and had vacuum again, the output would $#!& back to my feet.

 

IIRC, there is also a vacuum tube running to the water shutoff valve under the hood, but I don't recall which way that defaults when you lose vacuum.

 

If you don't have the ball, start by replacing it and then see what happens.

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I would dare say the coolant shutoff valve defaults to hot, unless mine is stuck.

 

My vacuum line is currently disconnected (and has been for a few weeks now, long story) and I have hot air at the defrost vents.

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