rgs80074

Hello everyone,

I have a 96 grand cherokee limited with a 4.0l engine.

I have a number of issues with the jeep (but with all the issues it has i'd have no problem jumping in it and driving it cross the country its got issues but its been reliable as any other vehicle i've had).

anyways when I bought the vehicle I swear it had heat and defrost. living in florida heat is not an issue you run into often but more defrost than anything. I can swear the defrost used to work no problem.

but now when i put on the heat or defrost it just puts out cool air which when your trying to defrost a fogged up window in the middle of the night is not very helpful.

now my ac compressor has bearings going bad, to the point I can not turn on the ac or i get a variety of issues like noises, engine drag etc, when the ac is not on its fine (need to really get to replacing the bearings, compressor or getting a bypass for now but that would require removing the ac compressor which i don't want to do).

so my question is since the ac compressor is going bad could that have an effect on my heat/defrost? if not maybe the heater core had issues before i bought it and it was bypassed but I swear I used to have heat/defrost in it.

guess if thats the case (bypassed heater core) given how little i need the heat/defrost i might be better off getting on that plugs into a cigarette lighter and use that if/when needed.

any help would be appreciated.

ryan

wingless

This reply shows the interior of the heater box on my manual control ZJ. The vee shaped door directs the airflow through the heater core (not installed), or bypass the heater core.

This reply shows the bottom of my heater box and the electrical motor that moves the vee shaped door that controls airflow through the heater core, to the right of the yellow circle.

If the issue is control of output airflow direction, then that is likely a vacuum problem.

BlueRidgeMark

Two separate problems. The cool air on defrost is because your heater core is not getting into the act. On most vehicles, the defrost setting turns on the AC and then cools the air to get the moisture out of it, then runs it over the heater core so you get hot, dry air blasting on your foggy window. Works well.

So, you have the cooling part, but you aren't getting the heating. That's either a controls problem (including a possible vacuum problem), or your heater core is plugged.

The compressor problem is the easy part. Replace it! Of course, you need the right tools for that due to the AC refrigerant, or you need to pay a mechanic to do it. I was quoted $1000 for the job on my WJ, so I bypassed it.

rgs80074

hello,

no issue with air flow if it set it to defrost it comes out the defrost vents, if i set it to the other vents it comes out of them.

the issue is its no longer putting out heat and I swear it used too but in florida is not something used often especially the heat, the defrost more.

so it sounds like the ac compressor thats going bad (bad bearings) is not causing it not to heat up but it does get used which explains another symptom that happens when the ac is turned on, i can not run the vehicle iwth the ac on due to the noise, no power i assume to the extra work drags down the engine.

so if i recall right and i used to have defrost/heat then its not likely a bypassed heater core but how can you tell if its been bypassed easily.

i don't think there's a vacuum leak i don't hear any hissing or anything like that, so even changing form cool to heat/defrost uses vacuum? ok I am not really a mechanic just try to do as much as I can as money does not grow on tree's. well i guess they do but my grandfather never did tell me where the money tree was all i know is it was in the back yard, i searched over and over and never found it. where or what vacuum line should i be looking for and where at, in the dash or under the hood? and the other possibility is a bad switch, i'll have to look at seeing how much that is to replace, all these things just get added to my want to fix list although if i got the ac and window fixed this would probably become my daily driver again over the kia soul.

and if for some reason its a clogged heater core, first how would i test that? how would it have gotten clogged isn't it a sealed system for the most part?

and thank you all for your respones.

ryan

dave1123

Yes, it's a sealed system except for temperature expansion control, but if you don't have adaquate rust control, as in antifreeze or water pump lubricant in it, the block and head can rust internally and that rust can plug radiators and heater cores. Being a FL car, I'm assuming you don't have much but water in it, right?

The blend door controls temperature and is controlled by a stepper motor (electrical) unless your heater panel has a slide lever to raise and lower heat temp. In Wingless'es second reply photos, the small box with the red label on it is the motor, just to the right of what he has circled.