1998 5.9 ZJ HVAC

[macgyvr]

1998 5.9 ZJ with 236k.

When you are driving in the summer the a/c is cold while you are driving. While you are stopped, it gets hot and there's a slight smell of burning oil.

In the winter, when you are driving the heat works great. While you are stopped, it gets cold.

I played with the Freon in it. I thought maybe it was low. I tried to add a can and it appeared to be way over filled. It was maxed out on the gauge. I then put just the gauge on it without trying to put a can of Freon in. I watched the gauge as the Jeep idled with a/c at max. It would show maxed out over filled until the fan kicked on. When the fan kicked on it would go back in the normal range. Once the fan kicked on it would slowly build pressure until it was maxing the gauge out. The compressor would kick on and off, once the fan kicked on again it would go back into a normal range and repeat. The a/c was warm to just barely cool while doing this.

I have no clue if the odd operating of the a/c is related to the heater being cold at stops or not.

The 5.9 from the factory has an electric fan and doesn't use a mechanical fan at all. The jeep appears to be cooling normally.

mac 'not sure where to start' gyvr

 

[altrocker1]

Does the 5.9 use vacuum to control the blend door or is it cable or electric operated? I don't think its vacuum activated, but if it is, its possible you have a vacuum leak.

As far as the pressure spikes, you should only be reading the gauge when the compressor is engaged. That's when you should get an accurate reading and it will be much lower than when the compressor is off.

 

[macgyvr]

I am not sure how the blend door is engaged.

The odd thing about the pressure is that its building while the compressor is engaged. The compressor shuts off when the pressure is up to OMG. Then the fan kicks on, because the radiator is at the temp where it turns the fan on, and everything falls back to normal....but the a/c isn't cold like it should be...just cooler than completely warm.

I read on another forum where the fan is supposed to kick on when the a/c is on and run on the low speed setting all the time. I'm wondering if I don't have a fan issue with it only running on the high speed setting.

mac 'silly gremlins' gyvr

 

[IllianaXJ]

Blend door and mode door are electric.

My 01 XJ was programmed to run the e-fan when the rad temp was 215* (maybe?) and when the A/C pressure was at a certain level. Maybe your A/C pressure switch isn't communicating with the PCM to run the fan when the A/C is on?

 

[macgyvr]

I am with you on the a/c fan not running when the a/c is on could be part of the a/c problem...

but would it be related to losing hvac at stop lights for both a/c and heat?

Apparently if you ground the sensors out for the low and high speed fan sensors you can force the fan on at anytime. So I might run a two pole switch that is ground to both sensors and then I can make the fan work whenever I want. If I forget to turn it on, the high speed will still work (I think the low speed sensor isn't turning the fan on).

mac 'at least I think' gyvr

 

[Talyn]

I would get it checked with a proper machine and make sure it is at the correct charge. You seem to indicate that it is still over charged. This can also damage the compressor.

As you sure that both the low and high speed switches are coming on at the correct temp?

On the heat, its a bit of a pain to fully bleed the cooling systems in these. I would check that. Do you hear a water rushing sound when you first start it? Also, a little leak can easily draw in air in to the cooling system. What temp does the engine run at when you lose heat? Have you flushed the heater core?