climate control circuit repair
07-18-2010, 10:38 PM
#1
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climate control circuit repair
Hi All.
Recently had an issue with the climate control on my '84. The unit was turned off, and I turned it on to the defroster and within approximately five seconds smoke began coming out from the front of the unit. I immediately turned it off and finally got around to opening it up to see what happened. The results are below.
I there any way to repair the board, or are there replacement boards?
Thanks in advance.
http://forums.rennlist.com/upload/bu...rd_1_copy1.jpg
http://forums.rennlist.com/upload/bu...e_up_copy1.jpg
http://forums.rennlist.com/upload/fr...cuit_copy1.jpg
Recently had an issue with the climate control on my '84. The unit was turned off, and I turned it on to the defroster and within approximately five seconds smoke began coming out from the front of the unit. I immediately turned it off and finally got around to opening it up to see what happened. The results are below.
I there any way to repair the board, or are there replacement boards?
Thanks in advance.
http://forums.rennlist.com/upload/bu...rd_1_copy1.jpg
http://forums.rennlist.com/upload/bu...e_up_copy1.jpg
http://forums.rennlist.com/upload/fr...cuit_copy1.jpg
07-18-2010, 10:51 PM
#2
Rennlist Member
Hi Keith,
Am I seeing just one fried trace on the PCB?
If so, you may be able to just solder in a trace bypass wire.
Also follow the other traces and check continuity, WYAIT.
Am I seeing just one fried trace on the PCB?
If so, you may be able to just solder in a trace bypass wire.
Also follow the other traces and check continuity, WYAIT.
07-18-2010, 11:05 PM
#3
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Join Date: Mar 2010
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The trace is repairable, depending on the damage, either by just cleaning and reinforcing with solder, or with a bit of wire or component lead soldered along it.
The questions are:
1. Was the relay also damaged by this excess current draw?
and, more importantly,
2. What is causing this current draw?
Traces don't just burn up by themselves. You need to trace the wiring diagram to see what components get power through that trace... something along the way is shorted.
The questions are:
1. Was the relay also damaged by this excess current draw?
and, more importantly,
2. What is causing this current draw?
Traces don't just burn up by themselves. You need to trace the wiring diagram to see what components get power through that trace... something along the way is shorted.
07-19-2010, 02:27 PM
#5
Former Sponsor
You have a short circuit/high resistance between the control unit and the A/C compressor, which fried the trace and will have killed the relay.
This wire is unfused, which was a poor design.
The wire runs from the control unit to the de-icing switch, under the front windshield cowl. It then goes from there to the front of the vehicle hooking up to the low pressure switch on the dryer. Note that the wire in inside a loom, for this run and very seldom has problems. It goes from there to the 14 pin connector inside the engine compartment. From there it goes to the front of the engine, right above the air pump where there will be a single wire leaving the loom with a clear plastic connector (originally clear). The wire then splits and goes to the compressor and to the auxillary air valve that hangs on the front crossmember. 99% of the short circuits occur on the otherside of this connector. The wire that goes to the compressor can rub through and touch ground, the A/C clutch can have high resistance/short, or the wire can touch a ground going to the air valve.
If you send the controller to 928 International, they will forward it to me and I'll rebuild it. New relay, eliminate the trace with the new relay, cleaning, new bulbs, *****, calibrations, etc. Unit comes back with a custom fuse that you can connect to this circuit, so it doesn't keep cooking control units. If you request, we can rebuild your own unit and return it. Nice looking ones are getting harder to find.
This wire is unfused, which was a poor design.
The wire runs from the control unit to the de-icing switch, under the front windshield cowl. It then goes from there to the front of the vehicle hooking up to the low pressure switch on the dryer. Note that the wire in inside a loom, for this run and very seldom has problems. It goes from there to the 14 pin connector inside the engine compartment. From there it goes to the front of the engine, right above the air pump where there will be a single wire leaving the loom with a clear plastic connector (originally clear). The wire then splits and goes to the compressor and to the auxillary air valve that hangs on the front crossmember. 99% of the short circuits occur on the otherside of this connector. The wire that goes to the compressor can rub through and touch ground, the A/C clutch can have high resistance/short, or the wire can touch a ground going to the air valve.
If you send the controller to 928 International, they will forward it to me and I'll rebuild it. New relay, eliminate the trace with the new relay, cleaning, new bulbs, *****, calibrations, etc. Unit comes back with a custom fuse that you can connect to this circuit, so it doesn't keep cooking control units. If you request, we can rebuild your own unit and return it. Nice looking ones are getting harder to find.
07-19-2010, 02:34 PM
#6
Rennlist Member
You have a short circuit/high resistance between the control unit and the A/C compressor, which fried the trace and will have killed the relay.
This wire is unfused, which was a poor design.
The wire runs from the control unit to the de-icing switch, under the front windshield cowl. It then goes from there to the front of the vehicle hooking up to the low pressure switch on the dryer. Note that the wire in inside a loom, for this run and very seldom has problems. It goes from there to the 14 pin connector inside the engine compartment. From there it goes to the front of the engine, right above the air pump where there will be a single wire leaving the loom with a clear plastic connector (originally clear). The wire then splits and goes to the compressor and to the auxillary air valve that hangs on the front crossmember. 99% of the short circuits occur on the otherside of this connector. The wire that goes to the compressor can rub through and touch ground, the A/C clutch can have high resistance/short, or the wire can touch a ground going to the air valve.
If you send the controller to 928 International, they will forward it to me and I'll rebuild it. New relay, eliminate the trace with the new relay, cleaning, new bulbs, *****, calibrations, etc. Unit comes back with a custom fuse that you can connect to this circuit, so it doesn't keep cooking control units. If you request, we can rebuild your own unit and return it. Nice looking ones are getting harder to find.
This wire is unfused, which was a poor design.
The wire runs from the control unit to the de-icing switch, under the front windshield cowl. It then goes from there to the front of the vehicle hooking up to the low pressure switch on the dryer. Note that the wire in inside a loom, for this run and very seldom has problems. It goes from there to the 14 pin connector inside the engine compartment. From there it goes to the front of the engine, right above the air pump where there will be a single wire leaving the loom with a clear plastic connector (originally clear). The wire then splits and goes to the compressor and to the auxillary air valve that hangs on the front crossmember. 99% of the short circuits occur on the otherside of this connector. The wire that goes to the compressor can rub through and touch ground, the A/C clutch can have high resistance/short, or the wire can touch a ground going to the air valve.
If you send the controller to 928 International, they will forward it to me and I'll rebuild it. New relay, eliminate the trace with the new relay, cleaning, new bulbs, *****, calibrations, etc. Unit comes back with a custom fuse that you can connect to this circuit, so it doesn't keep cooking control units. If you request, we can rebuild your own unit and return it. Nice looking ones are getting harder to find.
I didn't know this was a service offered by 928 intl and yourself. Can you tell me the cost of the calibration? Mark A?
This offering requires a thanks from myself and the people who will do whatever they can to avoid confusing electrical operations.
07-19-2010, 04:23 PM
#7
Former Sponsor
Mark has had rebuilt climate control units for quite some time. Recently there was a problem with some of the rebuilt units he was supplied and he asked me to look at them and find out what was wrong. The replacement relays had continuity where they should not have had it, causing problems. The supplier didn't want to hear that there was some sort of "systemic" problem, so I've been fixing them for about a month, for Mark. I've fixed them, for myself, for years, intermittently. I won't install one without a fuse on that circuit (if there happens to be a short in the vehicle...like this vehicle obviously has....the short will smoke the new relay, if not fused), but Mark was never thrilled with my fuse location. Mark and I found a really nice, simple place to install a fuse, which should work very nice, for everyone.
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07-19-2010, 04:27 PM
#8
Mark has had rebuilt climate control units for quite some time. Recently there was a problem with some of the rebuilt units he was supplied and he asked me to look at them and find out what was wrong. The replacement relays had continuity where they should not have had it, causing problems. The supplier didn't want to hear that there was some sort of "systemic" problem, so I've been fixing them for about a month, for Mark. I've fixed them, for myself, for years, intermittently. I won't install one without a fuse on that circuit (if there happens to be a short in the vehicle...like this vehicle obviously has....the short will smoke the new relay, if not fused), but Mark was never thrilled with my fuse location. Mark and I found a really nice, simple place to install a fuse, which should work very nice, for everyone.
Thanks Greg.
07-19-2010, 04:28 PM
#9
Rennlist Member
Mark has had rebuilt climate control units for quite some time. Recently there was a problem with some of the rebuilt units he was supplied and he asked me to look at them and find out what was wrong. The replacement relays had continuity where they should not have had it, causing problems. The supplier didn't want to hear that there was some sort of "systemic" problem, so I've been fixing them for about a month, for Mark. I've fixed them, for myself, for years, intermittently. I won't install one without a fuse on that circuit (if there happens to be a short in the vehicle...like this vehicle obviously has....the short will smoke the new relay, if not fused), but Mark was never thrilled with my fuse location. Mark and I found a really nice, simple place to install a fuse, which should work very nice, for everyone.
Yet again you show that with experience comes value that quickly overpowers low price.
07-19-2010, 06:43 PM
#10
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good deal. really appreciate the detailed explanation Greg.
is the relay you speak of the one on the board or is there another relay on the main fuse block?
by way of explanation, my A/C was not working when I purchased the car, and during engine removal noticed the aforementioned shorted wire in front of the previously clear plastic connector. i thought i had tied the single wire up when i removed the A/C, but it is entirely possible, (and now proven definite), that I did a ****-poor job of covering it up and it has shorted to ground somewhere. i will trace down the little bugger and eliminate the shorting potential.
many thanks!
is the relay you speak of the one on the board or is there another relay on the main fuse block?
by way of explanation, my A/C was not working when I purchased the car, and during engine removal noticed the aforementioned shorted wire in front of the previously clear plastic connector. i thought i had tied the single wire up when i removed the A/C, but it is entirely possible, (and now proven definite), that I did a ****-poor job of covering it up and it has shorted to ground somewhere. i will trace down the little bugger and eliminate the shorting potential.
many thanks!
