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Was just looking at some readings on my Tech1 when my C68 system developed a major problem. Lost all control of the system.
One minute all was working OK, then it just developed a mind of its own doing different things. Sometimes one led was lit, or none at all and no control over it. Resetting power with fuse 18 and 43 (head and programmer) would reset display and look OK till I hit any button and it just locked up. Sometimes just dashes across the screen, fan would run and no control of anything, you get the idea. The interesting thing is the last year or so I would momentary lose control and could not change the button so I blamed it on the control head, dirty button or such. (But I had cleaned them twice over the years).
Pulled the control head cause it's easy to get out. Just on principal clean all the buttons, pins for board interconnect and a little soldering. Put it back in and was just the same.
While messing around with the fuses and evaluating the whole situation, all started to work again 100%, - days end OK. Then next day was back to same problems. My gut said it was probably the programmer so I pulled it. Checked the pin connections and some routine stuff. I thought it was bad so I located a part near me for pick in a few days
In the mean time took the programmer board in the house just to see what I can see. As I stared at it I saw the 4 electrolytic capacitors. Kind of reminded me fixing the Bose amplifier boards. So I got out my capacitance checker and checked them all. Three of the four were low some more than others (still might work) but one was 4 mfd on a 39 mfd capacitor. That’s just too far out of spec for me. I decided to install one temporary that was close to value.
Put it in the car and it all worked first time not problems. Put the old part back in, no work. Put the new cap in all is good. So I think I'm on to something and it is not to hard a fix if you have some electronic skills. I believe each capacitor if bad will give a different symptom.
I think a lot of these boards are failing due to age, and their not semiconductor related problems. After all, it is down by the heat vents, not good for capacitors as they might dry up sooner.
My plan was to get the correct capacitors and replace them all.
I am still going to also buy the new programmer just to have a spare since I got a good price on it (in today's prices) .
Now for some tech stuff if you care to stay longer. I have made a picture of the board so you can see what I am referring to. The "C" designations were arbitrary as there is nothing on the board at all.
All were 50 volt capacitors, seemed a bit excessive but I went with the same thing.
C1 - 39 mfd electrolytic measured 31 mfd and was probably still working. It has 8 volts on it and is the reference voltage in the programmer
C2 - 39 mfd electrolytic measured 4 mfd and was probably was not working enough due to low capacitance. It has 5 volts on which is probably the voltage for most of the TTL and logic. It was probably to low (under 5 volts) which caused my problem.
C3 - 22 mfd electrolytic measured 24 mfd and was probably still working. It has 1.80 volts on it when any button is selected other than off on the control head.
C4 - 100 mfd electrolytic measured 85 mfd and was probably still working. It has 12 volts on it which is probably main battery voltage in.
The 5 volt supply was probably right at the edge where it would tidier causing a intermittent condition. I have 2 pictures here so you can see it all. I think if you suspect the programmer as being bad, replacing all the capacitors might be worth a shot.
I left the case in the car with the vacuum lines attached, and just removed the board by itself. Seemed to be easier then messing with the lock nut for the vacuum lines.
(New pictures, deleted photobucket)
Not the end, only the beginning.
All is working OK now..
This is good news, and not terribly surprising. Electronics that are misbehaving and are the age of these cars or older, often only need to have the electrolytic caps replaced to restore them to good working order. Electrolytic caps are probably the components that are most susceptible to age-related failures, as the electrolyte dries up.
Replacement electrolytic caps are readily available from numerous distributors, including Digi-Key, Newark Electronics, Allied Electronics, Mouser, and even Radio Shack probably carries some values in stock, although it's been years since I've looked at their inventory.
So I went out to pick up the programmer I said I was going to buy. They allow you to plug in the box to check it out. I had the connecter hanging, plugged it in and it all checked out OK. The display was good and the relays clicked.
The box was a mess so decided to clean it up and I removed the board. Just for the heck of it I decided to check all the capacitors. All checked good except for the same one that was bad on my board. C2 measured 4.5mfd. The board works now but it's just a matter of time till it acts up.
So I am going to replace that capacitor and put it all back together for a spare.
So what do you think, are there more of these out there? I'll bet most of the programmers are on the verge. And it seems like it tends to be the 5 volt supply filter capacitor.
I realize this is only a sample size of 2, but I think it's got merit. How many of these programmers are laying in a pile and are repairable (for $1 in parts).
Thanks for posting the instructions on how to check and fix the programmer on my 95 vette; however, I don't know of anybody that can work / solder the new capacitors onto my board, so I will need to purchase me a rebuild replacement unit and do the removal and installation of the old / new programmer by myself. Can you please give me some instructions of the do's and don'ts of the removal and re-installation of the programmer? Anything that you can give me in regards to the removal and re-intallation instructions / sequence / told required would be greatly appreciated.
Andy - While I look for a write up I did on the removal of the programmer. Why don’t you tell us exactly and in detail what the symptoms and problems are. I would hate to see you spend $100-$400 and not get it fixed.
Thanks for replying. I posted a couple of weeks ago the problems which I encountered after I foolishly checked some fuses without having the battery disconnected. One of the fuses I pulled must have been the HVAC circuit and apparently caused the programmer to stop responding to the head control unit. As of now, all fuses are fine, I disconnected the battery for 12 hours twice to prompt a computer reset without any luck of fixing or resetting the heating / AC system. I have been driving the car on average 2 - 3 times per week hoping that a reset would just happen by luck....., but that does not seem to be working out for me. The head unit has power, at least the digital display's back light is lit, but no digital readouts or button control power to the individual push buttons. So it appears that the head unit for all intense purposes is dead besides lighting up the orange background display window. I had a very detailed reply from a member telling me that it sounds like that the programmer was probably my issues, and that he fixed his by replacing 4 capacitors on the programmers pc board. It sounds to me that I have the same issues with my unit, which is almost 20 years old now, and me having pulled and reinserted several fuses at random to find a blown interior light fuse while the ignition key was in the on position was maybe all that it took to kill the programmer. I am sure that I could find someone in the Raleigh, NC area that could trace the exact issues that I have out, but I already talked to a guy and he just told me that electrical issues could take a long time to diagnose, and that it could cost me $100.00's just to diagnose the problem..... So, here I am trying to save me hopefully some money by pulling the programmer out, hopefully find a local person that could check the capacitors for me, and if all possible replace them for me at a lesser cost then having to purchase a rebuild unit for $400.00 + online. So I am now trying to find out what it is that I need to do in order to remove, and then reinstall the programmer without causing any additional problems.
I would like to know if there was any initial problem as to why you were pulling fuses. And it is OK to pull fuses with the battery connected but would be good practice to have the key off. I have never heard of a problem occurring by removing a fuse with the battery connected, which is a common practice
It sounds to me like the programmer is a fault from what you have described. Please make sure that fuse #43 (and #18) is good, pull it and look at it or test it. Fuse 43 keeps memory alive in programmer but will re-learn when power is applied and buttons are pushed.
Someone who has no firsthand experience on the corvette and with these problems and no spare parts can really spend weeks muddling around with these kinds of problems and not just hours. Not to take anything away from anybody's expertise, but to come in cold on this problem is not the way to go and the customer will pay for the mechanics education.
To Remove Programmer
You have to first remove the knee pad from the driver's side for visibility. Screws on bottom and the star screws on side.
Look up to the right of the gas pedal and you will see a black box on the fire wall.
One screw (7mm) holds in the programmer.
The programmer won't drop down till you remove the connector.
Get a flashlight with lots of light. This is the hardest part. There is blue tab you push down and the connector will release, not easy to do. (there might be a locking pin in the connector - can't remember?)
Once that is done, the box will drop down where you can get to it.
The cardboard backing is held on with tape so just open it up so you can see the boards. Regardless if you are going to fix the programmer or replace it, it's easier to just replace the main circuit board. (Taking the vacuum lines off is hard as it has a non reusable lock nut) Once box is opened, remove 2 screws from the top board and let it hang.
Remove inter-board ribbon connector from the larger board by pulling it off by connector.
Then remove the 2 screws from the larger board and remove it.
You can then replace the board or work on it.
Observe electrostatic practices, don’t wrap in paper or plastic only ESD bags. (Careful with it, don’t throw it around. Even foam is better than nothing. No static discharges around it if you are in dry weather.
If you know somebody who knows how to work on printed circuit boards, removing components correctly and not destroying the circuit lands and who knows how to solder, then you can get the board fixed. This is a pretty easy job for anybody who has worked on circuit cards or an electronic technician.
Thanks for the instructions. The only initial problem which made me check the fuses was that the interior "bottom" compartments convenience lights did not work. I did find a blown fuse, replaced it, and the lights did started to work again after I installed a new fuse. I did trigger for several warning lights, who were displayed within the diagnostic screen, to come on from checking virtually every fuse I have, but all faults cleared out as soon as I disconnected the negative cable from the battery which allowed the main computer to reset all settings. Everything is working now as it should except the heating / cooling head unit.
So, I will check the fuses one more time to make sure that they are OK, and if they are, then I will have no choice but to pull the programmer out and have it worked on or replace it with a rebuild unit.
Thanks again for the instructions, and I will let you know after I get the system hopefully working again on what we found out about the issues that we needed to address in order to get the unit communicating again.
Andy
Originally Posted by pcolt94
I would like to know if there was any initial problem as to why you were pulling fuses. And it is OK to pull fuses with the battery connected but would be good practice to have the key off. I have never heard of a problem occurring by removing a fuse with the battery connected, which is a common practice
It sounds to me like the programmer is a fault from what you have described. Please make sure that fuse #43 (and #18) is good, pull it and look at it or test it. Fuse 43 keeps memory alive in programmer but will re-learn when power is applied and buttons are pushed.
Someone who has no firsthand experience on the corvette and with these problems and no spare parts can really spend weeks muddling around with these kinds of problems and not just hours. Not to take anything away from anybody's expertise, but to come in cold on this problem is not the way to go and the customer will pay for the mechanics education.
To Remove Programmer
You have to first remove the knee pad from the driver's side for visibility. Screws on bottom and the star screws on side.
Look up to the right of the gas pedal and you will see a black box on the fire wall.
One screw (7mm) holds in the programmer.
The programmer won't drop down till you remove the connector.
Get a flashlight with lots of light. This is the hardest part. There is blue tab you push down and the connector will release, not easy to do. (there might be a locking pin in the connector - can't remember?)
Once that is done, the box will drop down where you can get to it.
The cardboard backing is held on with tape so just open it up so you can see the boards.
Regardless if you are going to fix the programmer or replace it, it's easier to just replace the main circuit board. (Taking the vacuum lines off is hard as it has a non reusable lock nut)
Once box is opened, remove 2 screws from the top board and let it hang.
Remove inter-board ribbon connector from the larger board by pulling it off by connector.
Then remove the 2 screws from the larger board and remove it.
You can then replace the board or work on it.
Observe electrostatic practices, don’t wrap in paper or plastic only ESD bags. (Careful with it, don’t throw it around. Even foam is better than nothing. No static discharges around it if you are in dry weather.
If you know somebody who knows how to work on printed circuit boards, removing components correctly and not destroying the circuit lands and who knows how to solder, then you can get the board fixed. This is a pretty easy job for anybody who has worked on circuit cards or an electronic technician.
I have purchased a used programmer from a Corvette salvage yard, which came with a 30 day warranty, so I hope that I can exchange the "New" programmer this weekend and then have my original unit fixed per your instructions. I was wondering, just in case, should I have my car's battery disconnected when switching the boards from the donor programmer to my car? The last thing I need now would be to shorten out the donor unit. And just in case, what should I do, or try in case my head-unit is still not responding after the board switch?
I had Wayne Womble, from Womble Corvette in New Hill NC, change out the programmer on my car with the donor unit. Wayne called me earlier today to let me know that the head-unit is working fine again after the replacement unit was installed. He did tell me that he could not find anything wrong with my original programmer except that some of the solder connections had some signs of corrosion, almost like they were exposed to some moisture. Maybe the 1/2" of water which was puddled up on the driver and passenger side floor board after my car was damaged during the storm gave of enough evaporation moisture that the water was enough to cause the programmer to go out?
I do have one more question that you can maybe help me out on..... The body shop who repaired my car's storm damage told me that they had to add some air into one of my tires since it apparently had a leak in it..... I picked up my car and the Service TPMS System light was on which was a little strange. I checked the air pressure of the tire in question, and was a little stunned as my gauge read 75 psi. Could the actual sensor mounted on the rim gotten damaged from the tire's over inflation? The service light goes off after I start and drive my car for maybe 15 seconds or 300 feet.
Thanks again for your help with the programmer. You saved me a lot of money by not having someone guess around on what the problem may, or may not was.
Thanks Corvette Forum for the excellent thread! After much research, diagnostics, and pointless "easy fixes" which did nothing, I finally found this thread which clearly described my exact problem (complete freeze of the control head) and the step by step on how to repair. No reading of the FSM would have pointed me to this solution, and it saved me at least $165 for a new programmer unit, as well as at least $200 for a new head which I was about to purchase on the mistaken assumption that the logic circuit had failed.
Although I did wind up laying upside down in the driver foot-well for about 4 hours (remove and re-install combined), and removal of the circuit board WAS a remarkable PITA (as described) it was well worth it for a $4 total cost repair and a like-new functioning HVAC unit.
For about a year before the complete failure of the system I had been experiencing an intermittent failure of the "Outside Temp" reading (I wasted $50 on a new sensor which did not help), which then sent the HVAC into a series of random vents and temp selections. All of this is also fixed now.
The few things I would add are;
1) The cardboard backing on the programmer unit disintegrated right above my eyes as soon as I touched it. Wear safety glasses on this project if you dont want that stuff, as well as bits of filter foam, in your eyes. Wear a mask if you don't want to breath a bunch in.
2) The local electronics supply place did not have 39 micro-farad capacitors in stock. I used 33's and they work fine.
3) Have some solder wick on hand to remove the old solder from the PC board.
4) Use a good quality solder pencil with a fine tip. Some of the components on the PC board are very close. I started this work with a butane powered "general duty" solder pencil and quickly found it was too cold and crude to do the job well.
Was just looking at some readings on my Tech1 when my C68 system developed a major problem. Lost all control of the system.
One minute all was working OK, then it just developed a mind of its own doing different things. Sometimes one led was lit, or none at all and no control over it. Resetting power with fuse 18 and 43 (head and programmer) would reset display and look OK till I hit any button and it just locked up. Sometimes just dashes across the screen, fan would run and no control of anything, you get the idea. The interesting thing is the last year or so I would momentary lose control and could not change the button so I blamed it on the control head, dirty button or such. (But I had cleaned them twice over the years).
)
Great write up and thanks for the info and sharing your experience with the repair!
Any tips for getting the wire harness off? I've been trying now for about an hour 1/2 and it's not budging. There's just no room for any leverage at all. I've pressed the blue clip and can see it's now unhooked but the damn thing won't come out of the board connector. I don't know how you took being upside down and cramped like that but it's killing my back and neck.
01-26-2014, 12:40 PM
94 HVAC A/C failure - Programmer - *REPAIRED*
