HVAC Gremilins
 

I am having strange actions from my HVAC operation. I have read the damper threads, but wonder if this is the issues. 1993 C4 Cabriolet

With the AC running (Max cold, I live in the Florida Keys), fan speed Hunts from low to high periodically, and passanger side Foot Vent will go to maximum heat, cooking the passenger at random times, for random periods. The AC will then return to cold and the problem will dissapear for minutes/hours/days, then start again.

Any Ideas Guys?
Thanks

Sounds like it could be a servo misbehaving. At some point when it is acting up take the piece of plastic that covers the servos off and inspect the position of the passenger side servo. Then see if it moves as you change the temp setting from cold to hot.

If hot air is blowing out it *HAS* to be coming through the mixing bowl which is controlled by the servo. The only question I have is if the servo is malfunctioning, the AC control is malfunctioning, it is not fully closing, or if you actually have a leak in the paper heater ducts at the passenger's feet and you only periodically have a passenger in there to notice it.

Search this forum for heater servo and you should get a LOT of info.

If you are talking about the condenser fan hunting it's possibly a problem with the ballast resistor on top of the condenser itself. If it's the cabin fans, just ignore my suggestion.

If it IS the condenser fan it's likely to be cycling between no speed and full speed and the condenser will not be cooling the refrigerant sufficiently for the evaporator to cool the incoming air.

JD's suggestion of the mixing servos is just as likely too.

Regards

Dave

Dont know much about the fans, I know mine will only work when the climate is set to cold then when the car warms up, you can "gradually" turn the heat up and the fans will stay on. Go to far, the fans will shut off. I just put the windows down for now. Dont mean to steal thread but I need help too

As for the burning issue, I know my ductwork(aluminum flexpipe) that connects the tube coming up from the frame/floor on right side to the dash was dry rotted and a quarter size whole appeared, forced hot air out, melted my kickpanel and burnt the heck out of my ladies feet. Since Im in florida, I removed the pipe and stuck a 2.75" PVC threaded plug in there and was done with it until I go to the dealer or wherever to get the ductwork. Who needs heat, I need AC!!

The reason the cabin fans turn off as you turn the heat up is that there is insufficient air flow from the rear blower. Blocking the tube (there is one each side) doesn't help!! You get a similar effect is the fuse breaks for the rear blower.

The replacement tubes are really cheap from the dealer - I'd guess around $20, perhaps less.


Regards

Dave

It was just a quick fix to prevent forced hot air getting in. I havent run the heat since it came down from Philly in December and the hose was connected then. I will do a big trouble shoot one of these days. Thanks for the price estimate. I hate the way the dealer man looks at me when I walk in the door...like a fat man lookin at pie!!!