Voltage drop from 14 to 12 when turning A/C (L83 swap)
12-28-2018, 05:35 AM
#21
Teching In
Thread Starter
Join Date: Sep 2016
Posts: 21
Likes: 0
Received 0 Likes
on
0 Posts
afaik, the signal to tell the ecm to turn on the a/c compressor are on the can bus and come from the ac module in the cab so there's not yet an easy way to have the ecm turn the ac compressor which is the wire you mentioned (it is an output from what you said i believe)
if its the stock alternator it should do fine to keep up with the requirements you have, and it should be regulated by the ecm so i'm wondering if there's something missing that is goofing that up or that it is just idling down too far when the ac engages. i'm not sure what the strategy is for the ecm to change the output voltage.
might check out this thread, might be a band aid for your situation if there isn't a way to keep the rpms up when ac engages.
https://ls1tech.com/forums/conversio...hrow-away.html
another option might be to raise the target idle rpm in the tune to see if that helps any though the tradeoff is having a higher idle speed when not necessarily needed...never know though if it only takes 50-100 rpm might not be noticable and an easy way to solve the problem.
i'd like to know how this turns out so please follow up if you can
if its the stock alternator it should do fine to keep up with the requirements you have, and it should be regulated by the ecm so i'm wondering if there's something missing that is goofing that up or that it is just idling down too far when the ac engages. i'm not sure what the strategy is for the ecm to change the output voltage.
might check out this thread, might be a band aid for your situation if there isn't a way to keep the rpms up when ac engages.
https://ls1tech.com/forums/conversio...hrow-away.html
another option might be to raise the target idle rpm in the tune to see if that helps any though the tradeoff is having a higher idle speed when not necessarily needed...never know though if it only takes 50-100 rpm might not be noticable and an easy way to solve the problem.
i'd like to know how this turns out so please follow up if you can
Im talked to my tuner he told me he can fix the problem only if the A/C is controlled by the ecm and I’m not sure if it connected. but now I’m thinking about maybe the issue is like you said about the idling rpm is not enough when the A/C engages.
I tuned my truck before installing the A/C compressor so maybe that’s the problem. I just need to figure out how to make it work with the ecm so even at the higher rpms it should disconnected automatically to prevent damages in the compressor.
but for sure I’m going to try to rise the idle a little bit and seeing if that’s work
12-28-2018, 05:48 AM
#22
Teching In
Thread Starter
Join Date: Sep 2016
Posts: 21
Likes: 0
Received 0 Likes
on
0 Posts
If you rev the engine up to a higher RPM, does the voltage go back up to normal?
Did you swap the throttle plate to a throttle cable?
My gut feel is that it's not the charging system, but rather the low RPM. The charging system can't possibly supply the demand when the engine RPM is too low. So what could be causing the low RPM? You would think with a 2015 engine management that the ECM would increase the idle speed when the A/C comes on.
Maybe the tune has a mistake where the A/C RPM is low.
Did you swap the throttle plate to a throttle cable?
My gut feel is that it's not the charging system, but rather the low RPM. The charging system can't possibly supply the demand when the engine RPM is too low. So what could be causing the low RPM? You would think with a 2015 engine management that the ECM would increase the idle speed when the A/C comes on.
Maybe the tune has a mistake where the A/C RPM is low.
So you are saying that I should rise the rpm just I little ?
12-28-2018, 07:58 AM
#23
I have a 2016 gmc sierra, it does have a voltage regulator. You will see the voltage drop at times, this is normal. Even with the ac full blown you will see a drop. It will start at around 14.4 give or take when the truck is running and will go down pretty quick to hover around 12. It will jump back eventually. As far as the sluggish feel goes, i tuned mine because i hated the AFM. I changed shift points, firmness, throttle response etc... i took off AFM but lost 3+ mph. So i ended up turning it back on and kept changing the settings to compensate for it. But the voltage drop is normal. From what I've read its to help on gas mileage.
12-28-2018, 12:53 PM
#24
11 Second Club
As it'd be good to get a tach on there to see where your engine rpms are. As you say it sounds like it's going to stall it's probably too low. Hopefully you can get the a/c tied into the pcm & have it setup correctly to compensate. Keep us updated.
For a joke. I remember, on a carb car, having to set the idle. You'd have to set the idle with the a/c on & in drive. As it'd be high in park w/ a/c off. If just set at idle w/ a/c off the car would stall on the road with the a/c on. Lol. Old school.
For a joke. I remember, on a carb car, having to set the idle. You'd have to set the idle with the a/c on & in drive. As it'd be high in park w/ a/c off. If just set at idle w/ a/c off the car would stall on the road with the a/c on. Lol. Old school.
01-06-2019, 09:53 AM
#26
I don't mess with the stock ECU's but shouldn't the ECU try to keep it at the target idle speed regardless of load?
Maybe the throttle blade is set closed further than it should be and the IAC is already open so far that it can't add enough air in to maintain idle. I know on the Holley systems I've tuned you have adjust the throttle blade so that the IAC is at 5%-15% so that it's within range. Otherwise it can't control a slow or fast idle condition.
There is a bush fix, Just rig up a so that it's triggered when the AC is turned on.
