Low voldtage out of ECM for A/C relay, clutch won't engage
07-01-2006, 08:42 AM
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Low voldtage out of ECM for A/C relay, clutch won't engage
95 Civic DX, DB15B7, OBD0. Okay, I've gone through everything else, even changed out a few parts that tested okay, just to make sure, and my final conclusion is that the ECM ground is creating so much resistance to ground that only 9.5 volts are going across the relay, which is obviously not enough to engage it. Anyone else have this problem and able to fix it without replacing the ECM?
List of things checked:
Clearance on clutch plates
Clutch relay - (replaced with new anyway)
Pressure Switch
Diode
Fuse - (replaced 20 amp anyway)
When I jumper the relayed side, clutch engages fine, no issues there. When I tested the relay, I used 12 volts directly, worked fine. When I checked the voltage from the + side going to the relay directly to ground, it was +12V. When I checked ohms from ground lead to ground directly, it was extremly high, about 2000 ohms. Checking the voltage across the + and - terminals only registers 9.5V. According to the book (Honda Service manual), it's the ECM that regulates ground resistance. Any suggestions, besides replacing the ECM would be helpful.
List of things checked:
Clearance on clutch plates
Clutch relay - (replaced with new anyway)
Pressure Switch
Diode
Fuse - (replaced 20 amp anyway)
When I jumper the relayed side, clutch engages fine, no issues there. When I tested the relay, I used 12 volts directly, worked fine. When I checked the voltage from the + side going to the relay directly to ground, it was +12V. When I checked ohms from ground lead to ground directly, it was extremly high, about 2000 ohms. Checking the voltage across the + and - terminals only registers 9.5V. According to the book (Honda Service manual), it's the ECM that regulates ground resistance. Any suggestions, besides replacing the ECM would be helpful.
07-01-2006, 01:00 PM
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Re: Low voldtage out of ECM for A/C relay, clutch won't engage (Go-kartolddude)
maybe you have a leak in the a.c. system. if there isn't enough refrigerant, the compressor/clutch won't kick on.
07-01-2006, 01:04 PM
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Re: Low voldtage out of ECM for A/C relay, clutch won't engage (aak)
No leaks, pulled vacuum for 1 1/2 hours at 27. Sealed and let sit for another hour to see if any losses. Pressure switch was checked while compressor was engaged, showed to be working properly.
08-03-2006, 06:48 AM
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Re: Low voldtage out of ECM for A/C relay, clutch won't engage (Go-kartolddude)
I have exactly the same problem on my son's 94 Del Sol. It works great if you jumper the clitch relay. I took it to Honda to check out the ECM. They said that there was a ground problem in the ECM and that it has to be replaced.
New one is $800 from Honda, reman is $400. I didn't do it yet. I am looking for a reman unit on the internet, but haven't found one. There are several used ones on ebay, but I'm wooried about going that route.
In the meantime, I ran him a toggle switch to the clutch and he cycles it off and on. I know this is risky since he could over-pressurize the system, but he is using it temporarily until I can find a lower cost ecm.
New one is $800 from Honda, reman is $400. I didn't do it yet. I am looking for a reman unit on the internet, but haven't found one. There are several used ones on ebay, but I'm wooried about going that route.
In the meantime, I ran him a toggle switch to the clutch and he cycles it off and on. I know this is risky since he could over-pressurize the system, but he is using it temporarily until I can find a lower cost ecm.
08-03-2006, 06:50 AM
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Re: Low voldtage out of ECM for A/C relay, clutch won't engage (scofnc)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by scofnc »</TD></TR><TR><TD CLASS="quote">I have exactly the same problem on my son's 94 Del Sol. It works great if you jumper the clitch relay. I took it to Honda to check out the ECM. They said that there was a ground problem in the ECM and that it has to be replaced.
New one is $800 from Honda, reman is $400. I didn't do it yet. I am looking for a reman unit on the internet, but haven't found one. There are several used ones on ebay, but I'm wooried about going that route.
In the meantime, I ran him a toggle switch to the clutch and he cycles it off and on. I know this is risky since he could over-pressurize the system, but he is using it temporarily until I can find a lower cost ecm.</TD></TR></TABLE>
I'd go to a junkyard for a cheaper ECU and investigate with that. I would bet money that you issue isn't your ECU though...
New one is $800 from Honda, reman is $400. I didn't do it yet. I am looking for a reman unit on the internet, but haven't found one. There are several used ones on ebay, but I'm wooried about going that route.
In the meantime, I ran him a toggle switch to the clutch and he cycles it off and on. I know this is risky since he could over-pressurize the system, but he is using it temporarily until I can find a lower cost ecm.</TD></TR></TABLE>
I'd go to a junkyard for a cheaper ECU and investigate with that. I would bet money that you issue isn't your ECU though...
08-03-2006, 06:54 AM
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it sounds like a ground
Either that or apressure switch, u said u only have 9.5v to the compressor - that obviously is'nt enough to engage the clutch like u said... doubt it's the ECU ground tho, or u'd have more problems, it's probably a different ground from somethign else in the circuit...
Either that or apressure switch, u said u only have 9.5v to the compressor - that obviously is'nt enough to engage the clutch like u said... doubt it's the ECU ground tho, or u'd have more problems, it's probably a different ground from somethign else in the circuit...
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08-03-2006, 11:39 AM
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Re: (Syndacate)
If I am understanding what you've described, I don't think you guy's are having an issue with the ecu. You should be getting +12 from the ground on the relay, to the
+ on the battery. It sounds to me like their is a loose or poor ground connection in either the relay to frame, to battery - terminal.
+ on the battery. It sounds to me like their is a loose or poor ground connection in either the relay to frame, to battery - terminal.
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