A/C Expert Help Needed

A little background 1st.
Wifes 97 GMC Jimmy, 3 weeks ago I replaced the leaking intake gaskets. I also flushed the heater core since she had no heat. After all back together she now has heat and no more coolant leaks from the rear of the intake. As expected now she has a very very slight heater core leak. It doesn't leak enough to make the floor wet or use any noticable amount of coolant, but just enough that I can smell it. I plan to do the heater core replacement ASAP, know the basic details that the job requires, until now we have another problem :banghead: & I'm not sure if it is related. I noticed the last 2 days that the condensate that drains on the ground is more than usually seen (I know its straight water as I collected about 1/2 cup in a glass last night). 2 days ago I noticed a crack in the top of the plastic cover that houses the A/C evaporator. Today I get a frantic call from wife that the car is on fire & the fire department is on the way. When I get there I find the very top of the plastic cover over the evaporator is all cracked up and very hot like it was heat damaged. The area smells like burnt electrical. I think there is resistors in there & would like to know what they actually do or control. I had noticed that the A/C compressor does cycle on & off more often even though the Heat is ON & the A/C is turned off. I do know its supposed to cycle but why more often? Could the compressor be controls by this resistor? I plan to open it up tomorrow for a look see.

Any comments or suggestions would be highly appreciated.
Gene

The resistor pack, (located in the evaporator housing), is how the system changes the speed of the blower. Heater blower resistors are available at most auto parts stores.

A/c clutch cycles in A/C and defrost modes. Cycling rapidly is the result of a low refrigerant charge.

A BIG Thanks OldMaster!
I checked & appears that she has only one blower speed of high. Maybe the resistors fried & caused all the smoke. But I am surprised no fuses blew. Also, the A/C has always blown cold air, but ain't check that lately. I did move the compressor during the intake gasket replacement, but did not loosen or disconnect any hoses in the A/C system.

Thanks Again,
Gene

The blower resistor is comprised of coiled wires that look like springs. Each "spring" has a different resistance value that produces a different fan speed. The "springs" get red hot when in use. It's possible the resistor burned out on it's own. However, a very common problem is that mice will build a nest in the warm housing. I have seen them use everything from wool home insulation, to fiberglass, to newspaper to dog food. The resistor is situated in the housing in such a position that airflow from the blower cools it. If that path is blocked, it can overheat.

The HT6 compressor is VERY sensitive. When it is installed, the mounting procedure and torque specs must be followed exactly. If not done properly, the case WILL leak. If the case develops a leak, it's time for a new compressor.

Got the cover over the blower & evaporator off and removed the resistor pack. Everything in there looks exceptionally good with no signs of burning. Although the cover I removed basically fell apart because it was so brittle. So got to get a new one one of those. Guess that would be a dealer item. Further looking around all I could find was the Transmission vent tyewraped to the tip stick tube. It is obvious that it puked some fluid out that ran down some of the wiring harness & plug wires eventualy dripping on the exhaust manifold. I'm sure that coulda caused a moderate amount of smoke. Its hard to justify the problem without actually seeing it & the poor description from the wife (White smoke coming from under the hood on passenger side / sweet smell). When she called in a panic I instructed her to leave the hood closed (For her safety) and just stand back & watch it burn to the ground. I plan to move the tranny vent line to the other side like my 2000 Sonama, & go ahead & replace the heater core.

The only other question I have is how to get to the last bolt securing the evaporator & blower cover off? It is located between the fender & the side of the blower, about half way down.

Thanks Again,
Gene

Sounds like you've got it figured out. Very common for the housing to dry out and become brittle, and yes, dealer only item. Don't bother with used, you'll get the same thing as you have now...brittle. Transmission fluid and coolant will both give off white smoke when burning. The evaporator drain is very close to the exhaust pipe and if the heater core is leaking, coolant could drip on the exhaust pipe very easily, and give off that "sweet" smell.

As far as evaporator housing retaining bolts, the most difficult one to access is done from under the vehicle. If I remember right, it's behind a foil insulation heat shield. The heater core replacement is time consuming but is not difficult nor does it require any "special" tools. It would be worthwhile investing in a shop manual, be it a General Motors manual, ($65.00) or an aftermarket brand such as Haynes or Chilton, ($15.00). The GM manual is available online, the aftermarkets are available at most auto parts stores. If you're planning on a substantial amount of DIY repairs, I would strongly recommend the GM manual.

Thanks OldMaster,
Got the old heater core out & a new one in. Found it easier to just remove the dash completely for easy access to the heater core. Waiting on the new evaporator cover from the dealer which should be here tomorrow. The only 1 bolt / nut I can't get to for removal of the old cover is 1 nut about half way down between the fender & heater blower. Any ideas? I can see it but the area is to small to get a wrench down there. Maybe drill a hole in the fender well?

Thanks Again,
Gene

Glad to hear you've got the core handled. GM shop manual says to remove the dash completely, as you did. Every one I have done, I did the same way.

The elusive evaporator housing fastener you're having trouble with requires removing the inner fender. The fender itself needs to be removed also to replace the evaporator. Hope this helps.

Glad to hear you've got the core handled. GM shop manual says to remove the dash completely, as you did. Every one I have done, I did the same way.

The elusive evaporator housing fastener you're having trouble with requires removing the inner fender. The fender itself needs to be removed also to replace the evaporator. Hope this helps.

Again Thanks Old Master,
All done but the cover and that should be here tomorrow. But looking closer at the cover I found a line done the cover right at the area of the motor that "Cut Line" Like the new one might just overlap at that spot. I'll wait till I get the new one & see what it looks like.

Anyhow got more problems with my truck now (2000 Sonoma) with the ABS. I'll be posting bout that on a separate thread. Keeping up with my vehicles driving me nuts this past month. 1st wife's intake gaskets (Yes dex-cool), then a week later my sonoma intake gaskets went, this week its wife's heater core, and now just last night ABS light comes on in my sonoma. I figure once I fix that, next week my heater core will spring a leak.........:banghead: And that's when I was gonna do her ball joints.

Thanks,
Gene