Another maf burnoff thread
09-07-2018, 08:49 AM
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Another maf burnoff thread
I’ve searched and searched but can’t find any other cars who’s relays look like mine.
Can anyone label these for which is fuel pump, which is maf power and which is maf burnoff relay?
On the firewall, the relay on left is PN: 14078907. Relay on right on 14089936.
Every other picture I've seen has another relay mounted in the blank spot on my bracket.
09-08-2018, 09:41 AM
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Re: Another maf burnoff thread
Zackly:
A relay is just an electrically operated switch. From another thread; this one was re. the fan motor relay, but the principle is of course identical in all cases. Only difference in your case is that the ECM is commanding the relays rather than a temp switch.
IIRC the relays are nearly identical to begin with; only difference is, one has 4 terminals and is a form A ("make" contact only), and the other has 5 which is a form C ("changeover" contact). The 5th terminal makes its connection to the "common" terminal only when the relay is not energized and "breaks" when it operates, and doesn't matter to the 4-terminal circuit. Therefore you can use that part # in both places.
I suspect that the relay that's just hanging there used to be mounted like the others, in that empty spot.
A relay is just an electrically operated switch. From another thread; this one was re. the fan motor relay, but the principle is of course identical in all cases. Only difference in your case is that the ECM is commanding the relays rather than a temp switch.
A relay is a relay is a relay is a relay, as far as being "right"... it's just an electrically operated switch. A small signal (temp switch) controls a magnet (relay coil) that moves an iron piece that has the high-current contacts on it, and makes or breaks or changes over or lifts off, to switch the load (fan motor) on or off. It's a "make" configuration in this case. Gotta be the simplest thing imaginable.
I suspect that the relay that's just hanging there used to be mounted like the others, in that empty spot.
09-08-2018, 07:20 PM
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Re: Another maf burnoff thread
It’s not just sitting there it’s mounted there. Found the gm testing procedure for the code 36 I’m chasing and everything tests fine. Went scorched earth and ordered new power and burnoff relays and a new maf anyway.
Both relays test fine and the burnoff also is triggered by pcm and the wire lights up. Well see what happens when I replace it all.
Both relays test fine and the burnoff also is triggered by pcm and the wire lights up. Well see what happens when I replace it all.
09-10-2018, 08:00 PM
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Re: Another maf burnoff thread
The pigtail connectors can become borked over time. Your style looks newer...on mine, some of the wire jackets were starting to expose and a few of the wires were really loose in there. But, even with the newer style, get up close with them and make sure the connectors are still viable.
Mentioned above, MAF power and MAF burnoff relays are interchangeable. Swap to see if one makes a difference. Both of mine were bad and I ended up replacing both. It's kinda weird that two would go out, but, these cars are getting really old now.
That one should be screwed into the hanger for the relays...my guess is the holes in the hanger stripped, so at one point it was nailed to where it now sits to make it secure. If you want to make it original-looking, just use a longer bolt with a nut on the other side.
Mentioned above, MAF power and MAF burnoff relays are interchangeable. Swap to see if one makes a difference. Both of mine were bad and I ended up replacing both. It's kinda weird that two would go out, but, these cars are getting really old now.
That one should be screwed into the hanger for the relays...my guess is the holes in the hanger stripped, so at one point it was nailed to where it now sits to make it secure. If you want to make it original-looking, just use a longer bolt with a nut on the other side.
09-11-2018, 01:14 PM
#6
Re: Another maf burnoff thread
You can always use a newer style relay
https://www.thirdgen.org/forums/tech...-l98-88-a.html
https://www.thirdgen.org/forums/tech...-l98-88-a.html
09-11-2018, 01:47 PM
#7
Re: Another maf burnoff thread
I was chasing a code 36 as well. 86 Iroc Z, based on pictures, looks like the same setup as yours. I replaced all three relays in that location. Napa sells the appropriate relays. I'm not sure the information that the MAF power/burnoff relays are different, is correct. I am using the same relays there, with no more code 36.
AR255, "fast idle relay" (for both MAF power, and MAF burnoff) is what they call it, although it's not, for our application. Ordered two of them.
https://www.napaonline.com/en/p/ECHAR255?interchange=1
AR257, "throttle control relay" is the one for the fuel pump. I replaced it for good measure.
Both types are still made by Echlin.
AR255, "fast idle relay" (for both MAF power, and MAF burnoff) is what they call it, although it's not, for our application. Ordered two of them.
https://www.napaonline.com/en/p/ECHAR255?interchange=1
AR257, "throttle control relay" is the one for the fuel pump. I replaced it for good measure.
Both types are still made by Echlin.
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09-11-2018, 04:20 PM
#8
Re: Another maf burnoff thread
The original relays are different - I had my connectors swapped and that's what led to the code 36 in my case. I swapped them around and the code never returned. Also there are threads around here with pictures detailing that insides of the relays and they do have different resistors inside. Now it is obviously the case that only one of the two circuits needs the correct resistor (or doesn't need a resistor) and the other circuit will work with either relay - so if you get lucky and get the correct burn-off relay it appears that one will also work for the power relay but perhaps the voltage isn't quite right on the MAF power (or? Does the power relay have the resistor and having the wrong power causes the burn-off function to be out of range?!?). Does that mean it won't run? No because the computer adjusts for MAF output on the closed loop end of things. It may not read correctly when cold and I would suspect there would be some cold warm-up mapping issues. They may be insignificant..... this is all speculation and it may not matter in the least in practice but I can tell you FOR CERTAIN, that the relay ARE different, carry different part numbers from GM, and there is a reason for it. They wouldn't design it that way if all they needed was a generic relay - it would be cheaper obviously to use off the shelf parts not custom one's with carefully chosen resistors inside.
GD
GD
Last edited by GeneralDisorder; 09-11-2018 at 04:30 PM.
09-12-2018, 06:37 AM
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Re: Another maf burnoff thread
Pigtails and wiring is all fine and in great shape. This is a 3 owner 60k mike car that’s never been messed with. Also it’s interesting about the location of my relay. Every picture I’ve seen shows it on that bracket but looking at the bracket it’s not stripped - quite the opposite it looks like it’s never had anything screwed into it there.
Ive ordered NOS gm relays for both power and burnoff and have a new maf on the way (the newer one that doesn’t require burnoff wire). If it still throws a code after I’m going to just have someone program the prom to either delete the code or change the voltage sensitivity that throws it.
Ive ordered NOS gm relays for both power and burnoff and have a new maf on the way (the newer one that doesn’t require burnoff wire). If it still throws a code after I’m going to just have someone program the prom to either delete the code or change the voltage sensitivity that throws it.
09-15-2018, 07:22 PM
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Re: Another maf burnoff thread
Replaced all relays and installed a micro tech 49-1018
Drove it all day today and the lights gone. Only issue I have is the new maf doesn’t mount to the core support bracket and is only held on by the clamps. Don’t really like that. It’s also a bit larger and sits against the idler pulley. Not really sure what to do but for now it runs much better and no light staring at me.
Drove it all day today and the lights gone. Only issue I have is the new maf doesn’t mount to the core support bracket and is only held on by the clamps. Don’t really like that. It’s also a bit larger and sits against the idler pulley. Not really sure what to do but for now it runs much better and no light staring at me.
09-29-2018, 09:31 AM
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Re: Another maf burnoff thread
Few weeks and a few hundred miles later and light still gone. I’m fairly certain in my case it was the maf and not the relays.
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