Returd

On my drive today I set the temperature at 18 (Canadian vehicle so Celsius).this converts to about 64F. In any case what got was close to sweltering. I was alternating between 18 and cool (18being the lowest temperature setting). I had to switch about every 2-3 minutes being either too hot or too cold. Definitely a Goldilocks kind of day.

The best I could manage was to put into recirc, on 18 with front defrost going. This resulted in a slower heat up. After that I went into recirc on the cool setting with a jacket on.

Could this be the result of a clogged cabin filter or do I have bigger issues. The bummer is I just got the interior back in an cruise working in time to head out on this trip. My parts car spare hvac parts are back home, and I won’t be back for a month or more.

Any hints on what the problem could be will be appreciated. I’ll be a a friends place in a couple of weeks to do the timing belt. I’l have a chance to get HVAC repairs done while there, if I can figure out the issue.

Zerodrag

iTrader: (5)

Check to see if your heater control valve (on passenger side firewall) is working correctly (moving smoothly) when you are adjusting the temp ****. If I recall correctly, the arm should move s the **** is turned. My old one was leaking and was sticky causing the temp to fluctuate when I turned the ****.

Returd

Thanks, I'll check it out tomorrow. I put in about 1200 miles today. A good amount didn't need heat so just vented with no issues. I've noticed on start up I get about 1/2 minute of noise that I initially thought was my stereo.

Hard to describe but I'd say it sounds like a blend of short wave radio trying to tune in with a mix of "Luke you've turned off your targeting computer" kind of beeping thrown in.

t2d2

iTrader: (8)

I don't see how the cabin filter would explain it. That would block airflow, not create temperature swings.

HCV seems unlikely to me. That might mess up controlability or eliminate hot or cold ranges, but full swings like that doesn't seem like it's nature.

My guess would be the cabin temperature sensor, behind the little square vent by the ignition. That or some glitch in the HVAC unit, which is the computer for the climate control.

Returd

Well I think I got to the bottom of my HVAC problem. My air conditioning isn't working. I bought the car in January and thought I tested it as functional then, but being winter its apparent it was just ambient air blowing.

So i assume there's some onerous process to convert from 1992 vintage as to current that will have to happen.

Looks like time for another thread.....

Returd

I found this diagnostic for LS400's, is it valid for the SC ?

http://www.lexls.com/tutorials/air/accodes.html

Returd

oh also does anyone have any idea what would cause all sorts of strange HVAC noises on start up? Lasts about 30 seconds and sounds like a mix between radio static and fluid/vacuum going through a restriction

LoudonMan

Heater door problem, or low on gas. I have used 134a with no problems. Just make sure you add the correct PAG oil if you swap the condenser in the future.

Returd

What's PAG?

How would I diagnose a heater door problem?

LoudonMan

I use a vacuum hand pump, and have my grandson listen. He can hear better than I can. Too many loud cars and industrial noise in my past.
If you can't hear it operate, I jerk it out, and test it.

Returd

So by this I can assume the heater doors are vacuum operated?

Where do you connect to the vacuum? I assume somewhere on the firewall?

Guessing here but once the vacuum is hooked up you operate the doors with the engine not running by pouting the car in run and cycling through the modes?

Also what's PAG?

still learning this car.

LoudonMan

Hi.
Sorry for the vague answer,
Yes, check the heater with the engine running, and cycle through the ventilation from floor, upper, defrost, and recirc. Have somebody that can hear get on the passenger floor and listen for the operation of the heater box. You should be able to hear the doors operating. If not, there is a problem with the vacuum motor or the heater control unit.

PAG oil is simply refrigerant oil. You should probably go to a shop and have a tech check the gas for you if you suspect that low gas may be the problem. As you are experiencing cold air, then hot, I suspect that you may have some gas left in your system. If you are out of gas, Then you must first, find the leak and repair it, change the dryer, then add the proper amount of gas.
I hope this helps,
Gary

Returd

I had a very close listen yesterday and believe the noises I'm hearing are actually coming from the ABS. I changed a caliper and bled the brakes a week or so ago and inspect I may have pulled a bubble into the ABS.

Since I'm away from home and my tools I booked an appointment at a dealership in the city I'm visiting for a test/charge of the AC system.

I cycled through all the modes and the doors seem to be working correctly. I think my "too hot/too cold" is simply because the HVAC uses ac to temper and since the AC isn't working no cool air can be used to temper.

I'll post an update after my dealership visit.

LoudonMan

Please keep me posted.