1998 Frontier (288K miles)

[Cusser]

I've been lending my white 1998 Frontier (288K miles) to my daughter and son-in-law. Apparently 2 weeks ago when it rained in Phx, he tried to rotate the air controller to "defrost" position, and something broke. It turns out that in the approximately 10 years Kori returned the Frontier to us that we'd never rotated that knob to either "defrost" or to "heater" positions, just let hot air come right at us when we did use heat. So it broke with all the air coming out the windshield vents, the defrost position, couldn't adjust; that just doesn't suit as one NEEDS the AC in Phoenix AZ.

Anyway, on the 1998 Frontier the vent flaps are controlled by cables, and mechanism on the driver side of the air control box in middle of the dash, see diagram/photo.


I took at look at this today; first thing I did was to spray some cleaner/lube over the mechanism. Then I had to remove several dash and trim parts. The Haynes manual I have was actually considerably better for trim parts removal than the official factory service manual I have downloaded. Anyway, the mount for the cable sheath had broken loose, because the mechanism had gotten dirty and gummed up over the past 27 years. I cannot fathom anyone would go under the dash to try to clean and lube that every few years. Anyway, after getting enough access, I somehow freed up the mechanism and then used trial and error to get the air coming out the main vents only to driver and passenger, figured we didn't need under-dash or windshield air flow, as long as the AC worked, and heated air come come out the same vents. This took 2 hours, but was under the carport.

So after buttoning that up, I replaced the engine throttle position sensor with a new one, the correct part. And then had to turn off the air bag flashing light (I'd unplugged the harness passenger on-off connector to remove that trim piece). This part took another hour. It was only 109F in Phx today, now back up north now.

[Cusser]

Same 1998 Frontier, and I'm still "fighting" a slow refrigerant leak. Fortunately, this vehicle is an "extra" vehicle but I'll want to address this by fall.

I added 12 oz R134a in 2024, and another in Feb. 2025. The system has dye in it because I added some when I replaced the high pressure line in mid-2017 (pinhole leak). I have UV light/goggles and an electronic leak detector and bubble solution, and I just cannot find the leak. The compressor is still engaging but lines at firewall just ain't what they should be, so I didn't even attach the service gauges this time.

Once it cools down in September/October, plan will be to add 12 oz R134a and look for dye leakage with UV light in dark garage. I'll also take off the AC belt and try the sniffer with "the old storage bag around the compressor" trick and also check the evaporator case drain lines again. I did have a cracked low side cap a few years ago and lost some refrigerant, so I'll re-check that schraeder and replace if necessary. Even though I did buy pure R134a at store closeout for $6 a can, I'd rather find the leak and fix it right. Even if I need a brand-new compressor, I'm OK with that, I just don't want to throw parts at it without confirmation.

[JohnHere]

Cusser, you've probably already done these things, but have you "sniffed" all around the compressor seams? Also, have you checked along the bottom of the condenser, the top of the R/D where the lines attach, the inlet/outlet TXV connections, any metal lines down low (especially those having foam insulation, which could hide oil and refrigerant leaks), the dash vents, and the condensate drains?

If you have and still turn-up nothing, I think I would replace all the accessible o-rings under the hood, giving each one a light coat of Nylog Blue before buttoning-up everything. I'm presuming that the system is empty of refrigerant right now.

[Tim]

Let's not forget the O-rings on the TXV valve inside the case.

https://www.ackits.com/evap-nissan-fron ... ch=59-0011

[Cusser]

Let's not forget the O-rings on the TXV valve inside the case.

Good point, if I detect a leak in the evaporator core through vents or condensate tube.

If I do determine where the leak really is, I'll post here before I order the spare parts from you.

I also have a 2004 Frontier with same engine and AC, and that compressor seized at 103K back in 2018, so I have hands-on with compressor, condenser, drier replacement and line flush....