Cools fine, but a/c quits, fan continues blowing cold air, hit a bump and cold air starts again.

Sounds like a loose wire in the fan circuit

Low coolant, if there is an air pocket in the engine it will make it to the heater core. Once there , the air coming out is cold/cool. Once the coolant fills the heater core, it gets hot. If the coolant is fine hot or cold, then have the HVAC system scanned.

Make sure your fan clutch is working. No fan, no cooling of the condenser, no heat dissipation, no cold air. Start the truck and make sure you feel air movement, a lot.

check your blower moter connection it might be loose

They are right. It is difficult to find a bad or loose connection When the compressor is not cooling, open the hood and start moving the ac wires. You might be able to find it yourself.

You have to have a good air flow through the condenser..make sure the condenser is clean and clear of debris, dirt, leaves, ect....make sure the fan or fan clutch is working properly?

what you need is a new blower motor. It is located under/behind the glove box. The reason that it comes on when you hit a bump is because it jars the brushes in the blower motor to make better contact then when you hit another bump it losses contact.

first useing a scanner or temp gun check the actual engine temp. if it is hot check for fan opperation, air lock in the cooling system water pump operation I think youll find the prblem to be the fan

Hi!
It appears we have an Air lock scenario and you will need to perform a system Bleed.
Park the vehicle on level ground, when cold remove coolant filler cap, start engine and leave to idle, turn heater on full and blower to max. When engine reaches operating temperature watch and listen near coolant filler, keep clear as gurgling and hopefully a boil over should occur. Top up with very warm coolant and wait as it may do it again.
Check for heat inside vehicle if warm replace coolant cap but keep an eye on temperature gauge as the ~Air lock may have moved on from heater matrix/core so proceedure needs to be carried out again from COLD.

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Paul 'W' U.K

my 2000 dodge caravan heat sometime working sometime not working