Question about 1998 Jeep Cherokee

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Hello i have a 1988 jeep cherokee. i wanted to know how do i fix the vacuum line toe the heater control valve so i can get heat in the cabin?

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  • BRANDON Feb 26, 2009

    what if there is no suction from the vacumm line when i check the heater control valve?..... where could the problem lie?

  • Uriel Tello
    Uriel Tello May 11, 2010

    two vacuum hoses coming from inside the cabin one goes to the main vacuum supply the other to the control valve?



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  • 6,982 Answers

If line is really old, remove it and replace it. If you don't need to replace the entire length, put a short piece of small diameter steel brake line or other tubing in line where you wish to splice it. You can likely find a coupler made by a company called "help". Easy job!!

Posted on Feb 26, 2009

  • Richard Scordino Feb 26, 2009

    There should be no vacuum signal in that line unless the A/C is turned on. Note: If you have plastic tubing not rubber, to repair use small diameter rubber tubing and slip it over plastic line A small tie wrap at both ends will prevent any lack of sealing.



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1 Answer

Cabin heat

Yes, it might be hard to find such a diagram. Short of a factory service manual, I don't know. Perhaps a friendly parts person at a Chrysler dealership might be able to provide you a copy of how the vacuum lines connect, and how routed.
What you generally have is a single vacuum line from the engine going into the firewall and under the dash to the rear of the heater/AC control assembly. The line enters a fixture that can distribute vacuum signals through several hoses. One of those is the hose to the water valve, the only vacuum line that goes back into the engine bay. Selecting heat on the control obviously will send vacuum from the fixture to the water valve. The other hoses or lines connect to diaphragm operated door levers to control where air is sent.

See where the vacuum line for the valve goes back into the firewall. Then get on the inside and try to find that line-it may have broken or come apart. You may need to pull the heater control assembly out to get to the podlike fixture that the vacuum lines sprout from.
An alternative in this frigid weather, a make-do temporary fix, is to tee off a manifold vacuum line from the engine, and run a hose to the water valve. It will be on constantly, but it's winter, hey?

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There is a vacuum operated control valve in the heater core lines at right rear of engine-the passenger side of engine. If it is closed, no warm coolant will circulate through the heater core. The vacuum signal for it comes from the heater controls at the dash. If the valve is stuck in the closed position, it may need taken off and cleaned or replaced. If the vacuum signal is not working, you may have to pull out the heater control assembly and check that vacuum lines are still plugged into the back of it.

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If the coolant level is good, you could be having a heater control valve fault. Older cars used vacuum to actuate the valve, so if yours is vacuum operated it could be as simple as a split vacuum line. The valve could also be internally broken. It could also be a solenoid failing to ask the valve to open. Check for a bad vacuum line first. Good luck!

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Try checking the heater control valve. Follow the heater hose from the engine, and as you get closer to the firewall, you should run into it. It is in line with the hose, and should have a vacuum hose connected to it. Apply vacuum to the valve and it should move. If not, then replace the valve. If there is no vacuum when engine running and heater turned on, then check the hose for leaks or the vacuum source.

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Check the control valve on the heater core supply line to make sure the Vacuum line or control cable are connected and that it is opening properly.

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I have a 1997 jeep g c.. about 2 years ago i had to have a heater core put in it. since then i have not had as much heat as i had before. even on high i hardly have enough heat to keep the jeep warm...

You may have a vacuum leak affecting the vacuum supply to the control switch. I don't have the manual for your car, but if you have a vacuum operated valve on your heater hose, that could also limit the flow of hot water to the heater core. Look for the small vacuum line that goes from the engine intake manifold through the firewall to the control switch. Look closely at the connection to the intake manifold, as that is one of the primary failure modes. the other typical failure is the vacuum switch itself. If you can get to back of the control switch and pull the vacuum connector off the switch, check for vacuum on the supply line from the engine with the engine running. If you're getting a good vacuum there, your switch is likely the problem. Let me know if you have more questions.

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1999 cherokee heat question?

The valve would be connected in line in the heater hose going to the firewall often it will have a lever attached to it with a cable, can also be vacuum operated, look for a vacuum hose, if it has one. Most likely the heater core is plugged.

Mar 08, 2010 | 1999 Jeep Cherokee

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1988 Cherokee: When the heater is fully on, little heat

The valve that controls the water through the heater is not operating fully or the heater core is getting blocked.There is 2 hoses that go through the firewall to the heater core.If you look at the heater valve whilst someone operates it from inside the car,and you look in the engine bay,make sure the valve is working.Put your hands on the hoses and you can feel the hot water going through.(or not)Use this as a starting point and you may work out what is wrong.Hope this helps

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1 Answer

I have a 1988 jeep cherokee.... if im not getting suction from the heater control valve...... where could the problem lie?

If you are talking about the vacuum line going the the heater control valve, the problem can be the control panel or a vacuum line that feeds the control panel. The cherokee has a football shaped vacuum canister in the front bumper on the right side. Check the canister out for cracks or disconnected lines.

Feb 26, 2009 | 1998 Jeep Cherokee

1 Answer

Heater only blows warm air.

The hoses from your heater core should be very hot to the touch. Check the hoses going to the core from the water pump. It should be very hot. The return hose should also be very hot. Now check the hoses going to the core. If they are not the same temp, then your heater control valve is not working correctly or the vacuum is not working. At any rate, locate the vacuum line going to the heater valve. Remove the silver bar on the valve from the plastic plunger arm. You will have heat all the time now if it was only a vacuum problem. You can fix it later when it's warmer out. BTW a 200* thermostat will make your heater even hotter.

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