Corso

pcolt94, I just got done putting everything back together. I want to thank you for your thread and info. The cap was blown. And now thanks to you my 94's air works great. It's was one of the most frustrating repair job I've ever done but worth it. Again thanks.

Oh yeah, a tip that may help someone else. I used painters tape to hold the screws to the socket. Just run the screw through the tape and stick to the socket. It holds it in place and rips right off when the screw is tight.

mattavetteguy

Yeah, its not easy. After I broke the visible "tab" off the top, I then turned the box so I could see the back, removed the crumbly cardboard, and used a thin flat blade screwdriver to pry up the blue "latch" part of the connector which is just visible from the inside of the programmer box. I then used the screwdriver to apply upward pressure on the connector body while pulling down on the programmer box. It took a goodly amount of force to get it free, and about the same to seat it back into place when the repair was complete. It does snap in with a perceptible "click"

Stay with it- If I can do it so can you. Totally worth it in the long run. I think if I had to do it all over again I would remove the seat first.

WisconsinJake

To the original poster, pcolt94 - you sir, are a Corvette Forum hero.

Picked up a 94 LT1 6 speed over this winter, and spent weeks trying to figure out what was going on with the climate control. You saved me many hours and dollars...

Cliff Harris

If you replace the electrolytic capacitors with tantalum capacitors you will never have the problem again. They cost more but don't leak any electrolyte like the electrolytic capacitors do.

Cyclonite

OP.... PM sent

banditt1979

Excellent write up guys. Working on a 1990 with the same problems, blinking lights no codes. I am assuming the same idea will possibly work, replacing the capacitors. Mine has different value caps. Also on the 90, the vacuum lines are too short to drop the box down far enough to get anything done, so I ended up cutting one of them and was able to walk the washer off to remove the vacuum line bulkhead. Just in case someone wanted to do this to a 1990. Gonna replace the caps and cross my fingers!!

JMelton

The idea sounds promising replacing them with Tantalum, but given the potentially dangerous failure mode of tantalum caps (heat, smoke and fire) I'm wondering if it would really be worth it.

http://www.capacitorguide.com/tantalum-capacitor/


Replacing the existing caps with the same type should give another 15 to 20 years of service, and stay within the design scope the engineers envisioned.

Cliff Harris

I've never seen a tantalum capacitor fail in 50 years of working with electronics. I have seen electrolytic capacitors explode, though. That usually happens if it's put in backwards.

Opihi59

Searching for solutions for an A/C problem in my 94 and came across this thread. I have the FSM open in front of me and it seems to be pretty worthless for this. Just this AM I pulled out my speedometer/cluster and replaced the polarizing film on the LCD display, which now displays fine once again, but on driving it for the first time after this repair, the AC is not working right. None of the AC buttons respond, though it sounded like the compressor was running and I was getting a whiff of cool air on my feet as well as out the defrost vent. I was thinking that I had messed something up while pulling the speedo, but I did disconnect the Negative terminal on the battery before starting this job, and think this may have something to do with this new AC problem.
I turned the car off, then started it up again, and had control over the AC buttons and thought I had the problem solved but in less than a minute it shut down again and I had no button control. I did this one more time (turned car off, then started it again) with identical results.
While pulling out the programmer and replacing the capacitors is possible, I'm curious if there is a better way to work thru this problem before diving in to this process. I just had the AC system evacuated and recharged 2 weeks ago and it had been working fine up til now.

EDIT--Just so I don't leave this hanging for anyone searching this valuable thread, I did come up with a solution. It's in this thread in case it ends up being helpful.

grandspt

I hate to disagree with you but I have seen quite a few tantalum capacitors fail, shorting and smoking! I have also been in the electronics engineering field for over 50 years. The surface mount type are usually the ones that I have seen fail!
Also I noticed a post above where they could not find a 39uf capacitor so he chose a 33uf. It is always better to choose the next higher value not lower. Example if no 39 uf is available use a 47uf and always keep the voltage rating the same or higher. Keep the temperature rating the same or higher as well.

pcolt94

My thread grows

Just going to throw in my 2 cents from my 45+ years of commercial and aerospace engineering electronic experience. This is just my own experience and observation and not to disagree with any other comments. Just some general highlights and comments.

Electrolytic capacitors generally can go down in value with age, usage, time and temperature till they no longer work or cause strange symptom in the circuit. They also may short.

Tantalum capacitors on the other hand don’t seem to go down or change in value. They have some different characteristics with temperature and age. But I have seen tantalum polarized caps short. Mostly they were used as decoupling caps from a power supply feed and were generally a low value capacitor.

I am not a capacitor expert, but have seen and experienced a lot thru the years and I'm not done yet. There still more to learn.

ACECO

Even though this is an old thread, I just wanted to leave a quick note to thank pcolt94 for his excellent write up on this subject. My 95 developed much the same climate control symptoms over this past weekend. After much troubleshooting (and cursing), I discovered this thread later that evening. Next day after more cursing and contortions, I got the programmer board out, changed the caps and lo and behold, it all works again.

FWIW I had a couple 33uf, 35v tantalum caps so I used these, along w/new electrolytic caps for the 22uf & 100uf. My logic was the 35v caps were still 4+ and 6-7 times the buses they were attached to, so they should be fine, voltage wise. I suspect the original 50v rating is a bit of overkill, and may have likely been the result of the manufacturer only wanting to stock one value voltage rating to cover all uses vs having various voltage caps within the same uf/capacitance rating.

As to the tantalum caps, I'm not worried about their failure mode at this point. Doubt I will have any issues but if so and the car burns to the ground, so be it. Had the 95 for nearly 10 years now so this would give me the excuse I've been looking for to shop for a newer model.

Thanks again!

trebor8008

Good info

Speedball

Does this apply to the LT4 1996 also? This is news to many here in CA I'm sure, where except for heat we don't get weather.. : )

SPEEDBALL

Speedball

AC/Heater gone goofy....83,000 miles with great maintainence....CA car always garaged, suddenly heater/AC goes crazy alternating on and off and then the heater starts blowing steam in the outside of the windshield....(different problem soon to be fixed also...) This doesn't seem to be a solveable problem here in Sunny LA...until I found this on the Forum...off on a search for parts now....A big Thank You

SpeedBall

Brew14u

This is an old thread, but I wanted to thank pcolt94 and to add a few tips. My 1994 daily driver with C68 started locking up after responding to button commands for a few seconds once the key was turned on. I used pcolt94’s detailed and well written procedure to remove the programmer and replace the capacitors. I would not have been able to diagnose problem and make the repair without pcolt94’s guidance. I want to let pcolt94 know that his time and effort spent writing this up is greatly appreciated – thank you!

Mine has a manual transmission, so I don’t know if the clutch pedal changes the clearance, but after removing the single bolt that holds the programmer to the firewall and trying for 30 minutes, I could not get enough leverage to disconnect the electrical connector to drop the programmer down to an accessible level. Having just replaced the power brake booster for the second time in less than a year by unbolting and lowering the steering column to access the right brake booster nut, I used that same process to gain “better” access to the programmer.

Once the driver’s knee pad is removed, there is a metal reinforcement held in place by four 10 mm bolts. Two are to the left where the door is when closed and two are far right only accessible with a box end wrench because of the carpeting up the tunnel. Note that even though all four bolts are 10 mm, the two on the right and two on the left are different lengths and thread diameters, so they are not interchangeable. Once the four bolts are out, the panel slips out without any other things in the way or attached. Next use a 2x4 or other support under the steering column and remove two 15 mm bolts attach the bracket that supports the steering column. Once the bolts are out, remove the support and lower the column. At that point, I could see the programmer and electrical connector and was able to use a flat blade screwdriver to pry the electrical connector to disconnect. The electrical connector has a lip and I was able to insert the screwdriver between the lip and programmer and rotate the screwdriver to pry the connector off. Clearance is tight, but there is a small amount of play in the steering column once lowered and I was able to move the steering column to the left enough to drop the programmer down. From there, I followed pcolt94’s instructions verbatim to remove the programmer board and replace the 4 capacitors. My soldering skills and equipment are basic at best, but I was able to do it. I am not a mechanic or electronics tech and I tend to work slowly and methodically, so it took me an hour to get the board out (remove hush panel, reinforcement panel, lower steering column, remove electrical connector, and programmer board) and another hour to slowly and carefully replace the capacitors.

Reassemble in the reverse order. Once I got the programmer board back in and maneuvered it roughly into place, I put the steering column bracket back in. There is a bracket on the firewall that holds the programmer. At the bottom of the bracket there is a small lip that acts like a clip and holds the programmer in place and aligns the bolt hole while you put the single bolt back in. Reassembly took me about an hour.

I read several other programmer removal horror stories about twisting into a pretzel and various other painful positions, spending 5 hours cursing the electrical connector and not being able to get enough leverage to dislodge it, removing the driver’s seat and staring upside down for prolonged periods of time into the dash abyss, etc. For me, lowering the steering column was reasonably easy – 4 easy to get to bolts and 2 that were more time consuming, but I was comfortably sitting in the drivers seat while removing and replacing the two with poor access. For reference, I rank the programmer repair easier than brake booster replacement, ignition wire replacement, and power window motor replacement, but more difficult than antenna replacement and spark plug replacement. This forum is a great source of information without which I would not have been able to do these repairs.