MAF relay differences. They are not all the same - TPI - Third Generation F-Body Message Boards

elcam84 · 07-02-2007, 12:54 PM

Just informational...

It's repeated many times that the MAF power and burn off relays can use the same part. Well not exactly.

The MAF power relay has a couple added resistors to it that the standard 5 pin relay does not. You can see one of them in the inserted picture. There is also another resistor under the coil that you cannot see.

In the picture an original MAF burn off relay is on the left and an original MAF power relay is on the right. The added resistor is obvious.

If they were really interchangable GM wouldn't have made the modifications to the MAF power relay. They would have just thrown in a standard 5-pin relay. Also the aftermarket would have been the first to jump on that as their primary motive is to reduce part numbers.

Now the fuel pump relay and MAF burn off relay can be used interchangably but there are differences but not enough to cause an issue.

The correct GM part numbers for the relays are. GM Borg Warner and GP Sorenson.

GM 10067925 MAF power
GM 10094701 MAF burn off
GM 14078914 Fuel pump

BW R3009 MAF power
BW R671 MAF burn off
BW R761 Fuel pump

GP MR22 MAF power
GP MR82 MAF burn off
GP MR5 Fuel pump

My TPI has been doing some goofy things and it was at the time I did the swap and replaced the relays. I dug out the old relays and checked the current part numbers. Since the MAF power one was not the same number I needed to open it up and find out why.
I had always thought that the GM relays were pretty much one of two types 4 terminal or 5. After a little research they are minor differences in some applications. Yes any 5 terminal will work in pretty much all apps but they may not be exactly right and could cause issues due to missing internals.

Well after putting the correct power relay in my goofy issues have been solved. So make sure you buy the right relay. (my current relays were a year old and show no resistance with an ohm meter)

S10Wildside · 07-02-2007, 03:12 PM

It should be mentioned that this information applies to years prior to 1989.

Formula350Scott · 07-02-2007, 05:34 PM

Are the Maf power and burn off relays the same part number on the 89's?

IROCThe5.7L · 07-02-2007, 05:53 PM

Hmm, interesting. I have the same part number for both my power and burn off and no problems. That's good to know though, I always thought they were the same.

S10Wildside · 07-02-2007, 07:19 PM

Quote:

Originally Posted by S10Wildside

It should be mentioned that this information applies to years prior to 1989.

The relays for the 1989 system can be the same, GM # 14089936

This is the newer weatherpack style relay.

elcam84 · 07-02-2007, 09:55 PM

Quote:

Originally Posted by IROCThe5.7L

Hmm, interesting. I have the same part number for both my power and burn off and no problems. That's good to know though, I always thought they were the same.

I'm not sure why the difference. They are both controlled by the ecm in the same way. It stumps me why the difference.

All I know is that when I went to a GM relay with the same guts it runs better.

IROCThe5.7L · 07-03-2007, 08:24 AM

Quote:

Originally Posted by elcam84

I'm not sure why the difference. They are both controlled by the ecm in the same way. It stumps me why the difference.

All I know is that when I went to a GM relay with the same guts it runs better.

What was the problem before you replaced the relay?

elcam84 · 07-03-2007, 09:29 AM

I replaced all the relays whan I put the TPI in. Ran the same one for both MAF relyas like others have. Never ran quite right. I never could find a reason for the problems so I changed the power relay for a GM one and the drivability issues have cleared up.

The relays only had a few 100 miles on them. The relay in the picture is the original from the TPI that I dug out of one of my boxes to compare.

Stephen · 07-03-2007, 09:38 AM

On my 87 GTA, I was getting a SES code of my MA burn off, so I switched the connections for the fuel pump relay, suspecting that the relay was the cause. I figured if the fuel pump gave me issues, that would pretty much decide it, huh?

Well, the SES went away, but the fuel pump hasn't given me ANY problems.

I switched the connections back, as a double check...SES MAF burn off again. So, I switched the connections again, and that was around the end of last year. So, around 8 months now, with no problems.

IROCThe5.7L · 07-04-2007, 06:08 PM

Hmm, interesting. I have three relays on the driver side. I was informed the two round style ones were for the power/burnoff, and the square one is for the fuel pump. I actually have a brand new relay in my room with the part number: GM 10067925 and it is square, so I figured it was wrong (bought it for the MAF Power). But according the the part numbers posted in this thread, it says it is for the MAF power.

Stephen · 07-04-2007, 07:51 PM

Here is a pic of the relays I'm referring to, showing the 2 I switched the plugs on. The left, (inner most) one is stamped with MAF POWER.

The middle and right one, marked in the pic, are both 14078907.

Stephen · 07-07-2007, 12:39 AM

Found my notes...

They are both 14078907 relays. My SES code was code 36, MAF burn off relay.

By simply switching the plugs, my SES light went off, and I've had zero effects.

gta_knight · 07-08-2007, 05:20 PM

Quote:

Originally Posted by Stephen

Found my notes...
By simply switching the plugs, my SES light went off, and I've had zero effects.

So all you have done is plug the burnoff connector into the fuel pump relay and vice versa ? i might try that ! ive had a code 36 on my 87 GTA for ages now.

JB22 · 07-09-2007, 08:21 AM

I will just post to say that those arent the right part numbers for my 88.

Mine are the rounder style.

thunder85 · 07-10-2007, 04:33 PM

I have an 88 GTA, and my relays are the rounded off type as well. they both were the same part number. i am having an issue with my maf reading 5g/s when the engine isn't running... would this be a power relay issue? i have changed the burnoff relay (which resolved my 33 and 34 engine codes, just stuck now with incorrect maf values).

IROCThe5.7L · 07-10-2007, 10:30 PM

Quote:

Originally Posted by thunder85

I have an 88 GTA, and my relays are the rounded off type as well. they both were the same part number. i am having an issue with my maf reading 5g/s when the engine isn't running... would this be a power relay issue? i have changed the burnoff relay (which resolved my 33 and 34 engine codes, just stuck now with incorrect maf values).

My car runs fine. And when the car is on and not running, the MAF reads 5g/s. I think that's normal.

patgta · 07-13-2007, 02:00 PM

Nice post guys. I been having this code 34 problem for years. I have replaced the maf sensor and still no success, the code only comes up maybe once a month but it is still annoying. So i guess its either a bad relay, ecm or bad wire connection somewhere. I'll try to solve this problem with this new information. Thanks Pat

thunder85 · 07-14-2007, 03:03 PM

well, i am running a bit rich.. i have changed my coolant temp sensor, both relays, cleaned my maf, replaced ign module, etc. its not REALLY rich, just enough that when starting cold, i have to try several times to get it fired up. i can smell the gas, so i know its a rich condition.. and stepping on the gas to open up the butterflies helps it start quicker. any ideas? i can get more sensor values if it would help

skewbbasteve26 · 08-12-2007, 11:43 AM

I am so glad I founf this site... I was wondering if you could send me or post a picture of what color wires are going to these three relays MR22 MR82 and MR5. I have taken my relays off and don't remember the order in which they go. I have drawn up a picture of the pigtails and need to know what relay goes on what. I dont want to damage anything if I put them in the wrong place. 1986 Trans Am TPI 305.

resinlake · 07-11-2008, 09:02 AM

Really interesting posts. I swapped an 88 Iroc into an 85 that was just about 100% rust free and eliminated my heat/ac and all smog. I am getting Code 34. I de-screened the MAF, no loose wires or anything, how would I actually test to see what it is, relays or sensor that would be throwing the code? The cars just about ready to be put on the road but I'm concerned about drive-ability and yes even mileage if the MAFs f'd up. Thanks guys.

thunder85 · 07-11-2008, 11:56 AM

which relays did you use? the 85 maf burnoff and relay are not the same as those used in an 88.

resinlake · 07-11-2008, 08:23 PM

It was a fully swap, engine harness and body harness. Nothing remains in the car that was 85. It is all 88 except for the steering column.

pandin · 07-11-2008, 09:01 PM

If you open up the relays you will see the contacts are different sizes.

Control type relays have smaller contacts and power relays have bigger.

DC relays include a diode across the coils to prevent the coil EMF from spiking the driver transistor and shorting its life or arcing the controling relays contacts.

Resistors are added to control power flow (restrict in rush currents "soft start"). Also added with capasitors to filter the power harmonics (AC).

It is these spikes that cause random gliches in electronic circuits (MAF).

If you are controling a motor (fuel pump/fan) the contact inrush can be very high and the contact cut off spike very large (acts like a small welder).

resinlake · 07-13-2008, 01:04 PM

Interesting. I swapped in a CS144 alternator last week from a Fleetwood with 2 guage wire for the (+) and when I went to put the (-) lead on the ground post it was obviously acting like a welder if you know what I mean, there was a short somewhere or a great spike. Anyway, I let the car sit for a day and then tried again the next and was able to put the wire on the post with no arc back. Just made me go hmmm. I was even wondering why when I jump A and B on the diag port to read the code and turn the key my cooling fans come on. I know theyre hard wired to both run when the engine is running. Im obviously not an electrical genius. The fans were set up that way when I bought the car back in 02'

pandin · 07-15-2008, 10:30 PM

This info comes off the AutoZone Web Page

MR82
http://www.thirdgen.org/techboard/at...1&d=1216175175

MAF burn off
Part Number: MR82
Weight: 0.154 lbs.
Note: O.E.M. #10038792, 10094701, 14078907, 14078979

Gp-Sorensen / Relay - Anti-Lock Brake
MR82
Gp-Sorensen / Relay - Fuel Pump
MR82
Gp-Sorensen / Relay - Throttle Control
MR82
Gp-Sorensen / Relay - Fast Idle
MR82
Gp-Sorensen / Relay - Mass Air Flow Sensor
MR82
Gp-Sorensen / Relay - A/C Compressor Control
MR82
Gp-Sorensen / Relay - Radiator Cooling Fan Motor
MR82

MR22
http://www.thirdgen.org/techboard/at...1&d=1216175175

MAF power
Part Number: MR22
Weight: 0.15 lbs.
Application: With 4 terminals

Note: O.E.M. #10067925, 14039663, 14073412, 14078915

Gp-Sorensen / Relay - Fast Idle
MR22
Gp-Sorensen / Relay - Blower Motor Cutout
MR22
Gp-Sorensen / Relay - Fuel Pump
MR22
Gp-Sorensen / Relay - EFE Control
MR22
Gp-Sorensen / Relay - Air Pump
MR22
Gp-Sorensen / Relay - Upshift
MR22
Gp-Sorensen / Relay - A/C Compressor Control
MR22
Gp-Sorensen / Relay - Mass Air Flow Sensor
MR22 Note: Optional
Gp-Sorensen / Relay - Throttle Control
MR22
Gp-Sorensen / Relay - A.I.R. Control
MR22

MR5
http://www.thirdgen.org/techboard/at...1&d=1216175175

Fuel pump
Part Number: MR5
Weight: 0.149 lbs.
Note: O.E.M. #14078902 (14078914)

Gp-Sorensen / Relay - Amplifier
MR5
Gp-Sorensen / Relay - Aux. Engine Cooling Fan
MR5
Gp-Sorensen / Relay - Radiator Cooling Fan Motor
MR5
Gp-Sorensen / Relay - Fuel Pump
MR5
Gp-Sorensen / Relay - Anti Diesel
MR5

Notice all three will run fuel pumps (large inrush and large magnetic cutoff, EMF) , and the MR82 weights the most.

The MR82 has larger relay contacts then the MR22, and did not see the extra resistors in the GP relays.

pandin · 07-17-2008, 04:53 AM

Maybe this pic (from GM manual) will help to show how the resistors are used.

They are the zig zag lines across the coils (D & F) on the Maf relays. When used this way the resister helps to bleed off power when the control circuit breaks the connection.

It also makes up a LR circuit (type of filter) which is tuned to some frequency that will dampen oscillations when the circuit is energized.

Coils of wire act like electrical flywheels, slow to start and slow to stop (they store energy that can be used when the coil collapses).

Capacitors act like electrical springs (also can be seen as small quick discharging batteries).

Resistors are like a narrow place in a pipe (they limit the electrical flow and cause the power to turn into heat).

Note that the Maf power relay is controlled by the Fuel pump relay and is tied directly to the fuel pump motor. Any issues (shorts and intermittent connections) with the fuel pump and/or wiring will effect the maf power relay.

The Fuel pump motor is a brush motor, like a portable drill, ever see the lightning storm inside the motor, when running the drill under load.