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iTrader: (1)

I removed my air pump and all related parts (EGR too)when I replaced my fried main harness (engine fire). I put in resistors where all the unused connectors were. I read on this forum to use 33ohm resistors.

Well my car still had problems when I got it back together (and still does). To make a long story short, the ECU was bad and when I replaced it, the car ran pretty good (best I have had it running).

Then I had another problem (unrelated) and had to remove the UIM. When I did this I saw that the resistors were all fried except the air pump one; even the EGR resistor. So I thought maybe it had to do with the bad ECU. I replaced them. But when I turned the ignition on, I could see the port air bypass, split air bypass, and relief2 resistors all sizzling and smoking. The others are under the UIM and I cannot see them, so I do not know what they are doing.

I don't get a CEL but then again I don't know if it works because I have had so many problems and it never comes on and stays on, but that's for another thread.

Anyway, what would cause the ECU to send a siganal that would fry the resistors? I did some seaching on the forum and saw some conflicting info. Some said to use 330ohm resistors. Does anyone know the real values? Please help?!

InsaneGideon

33ohm resistors would soak up ~4.3W of power at 12V. and 3/4W at 5V, which some sensors run at.

Typically resistors are 1/4W, 1/8W, and 1/2W ranges (unless we're talking large power resistors here). Much much smaller than 4.3W. Not only does this kill the little resistors, but may also damage the ECU, if its connections aren't current limited.

I've never had to do anything like this to my 7. But I'd check the FSM to see what was supposed to be in each harness, look up the resistance ranges for those sensors/solenoids in the "inspection procedures", and place properly valued resistors accordingly.

jwhite94RX7

33 ohms is right for the three solenoids mentioned.

Use 10 watt resistors. Radio Shack might have them.

BOTTLEFED

iTrader: (1)

Thanx,
I thought 33ohms sounded right so I looked in the shop manual and it gave 26-32ohms for the solenoid resistance.

jwhite94RX7: Radio Shack should have 10W resistors? I bought 1/2W becasue that was all they had. I'll see if they can order me some 10.

jwhite94RX7

Sorry if that mislead you. It's been a while since I bought any high wattage resistors there. Their web site says they have 10 ohm resistors (here) but I don't see any 33 ohm resistors. You could string three in series, but that would be pretty ugly. You might try the 50 ohm ones. The ECU probably wouldn't notice.


Digi-Key has 30 ohm 10 watt resistors for about $2.00 but you'll get hit with a minimum order size charge unless you buy a lot of other stuff at the same time.

BOTTLEFED

iTrader: (1)

I'm getting more confused now. I went to Radio Shack to see what they had and I saw the 10W resistors (50ohm and 10ohm but no 33). They look like little bricks, not resistors. I know the ones the other guys are using cannot be these; they're HUGE. I looked at Rob Robinette's site becasue his turbo syst. simplification how-to has a picture of the resistor in the connector. See here:
http://www.rx7turboturbo.com/robrobi...lification.htm
So now I don't know what is going on.
Please help!

jwhite94RX7

The solenoids in the rats nest are different.
I don't know what their resistance is, but it's clearly much higher than the solenoids you're talking about.

If the resistance were 330 ohms instead of 33 ohms, the power rating would be 0.43 watts and a 1/2 watt resistor would work.

I checked the wiring diagram, and the solenoids you're talking about are running on 12 volts. To be safe, we have to assume the ECU doesn't reduce that. (In reality it typically will reduce it by about 0.7 volts.)

Power is voltage x voltage / resistance.

12 x 12 / 33 = 4.36 watts.

But running resistors at their rated power results in warm or even hot resistors. Since you will have them lying loose next to wires or hoses, you should double the power rating. That's why I suggested 10 watt resistors.

jwhite94RX7

This thread suggests that the rats nest solenoids are 330 ohms. The originator says he plans to use 330 ohm resistors ALL of the solenoids, including those of the ACV.

But it doesn't say that he was successful.

You're trying to fool the ECU into thinking that the solenoids are still there. Perhaps 330 ohm resistors will do that. Perhaps you don't have to duplicate the resistance of the original solenoids in order to fool the ECU. You might even get away with 1000 ohm, 1/4 watt resistors.

Trying high valued resistors is safer than trying low valued ones. Since you already used 33 ohms and the ECU didn't burn up (we hope!), there's no harm in trying higher valued resistors. They will be less load on the ECU circuits than the 33 ohm resistors were. If the ECU is happy and the resistors and the ECU don't burn up, you're in.

jetmech77

I had a similar problem....what I did to solve the problem is took the old sensors that had burned and basically put tape over them to hold them in. when the ecu does its magic it just accuates the electromagnets. It worked for me.... also I am assuming you put in a 49 state or maybe japanese air control valve right??

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iTrader: (1)

thanx jwhite94RX7,
I hope this has not hurt my ECU.
At first I was not sure how you were calculating the watts, but now it makes sense. You're definitely right about the 330ohm resistors; it can't hurt to try them and it sounds like the guys from that thread have not had any problems so far.

jetmech77: I didn't want all the sensors and solenoids plugged in and laying around under the UIM; that is why I went with the resistors.
I'm not sure what you mean by the air control valve?
I used a BOP set that I made myself, if that is what you are asking.

InsaneGideon

As long as you placed the 33ohm resistors where the ECU is expecting ~33ohm solenoids, the ECU should be fine. That only killed the resistors.

Careful with the higher power resistors. Depending on their case design (like the white sand filled "bricks"), they may have heatsink/airflow cooling requirements. If you can fool the ECU with higher resistances, you'll save this hassle.

BOTTLEFED

iTrader: (1)

InsaneGideon: I think you're right because when I checked the resistance of the melted ones the first time, their resistance went really high (>500ohms). If the the resistance had went down and the amps went up, then I may have something to worry about.
Thanx for the reassurance.

Cihuuy

i used 330ohm resistor 1/2 watts on all solenoid on the rat nest... no problem so far...

BOTTLEFED

iTrader: (1)

BTW, I got some 330ohm 1/2W resistors from Radio Shack yesterday, and today I'm going to install them in all the places where the 33ohm resistors are.
Wish me luck!

BOTTLEFED

iTrader: (1)

Thanx Cihuuy,
That's good to know.

If there is anyone else reading this that have done this, let me know. It would be nice to know for sure that the 330ohm 1/2W resistors are the ones to use in place of the solenoids. That way others that need this info in the future get the right ones and don't have to go through this.

Also, if I know that the 330s are the right size and I still fry them, I'll know something else is wrong.

Cihuuy

even 1W will work... I just solder the end of the resistor with a female/male end (forgot which one) and just make sure you cover it with electrical tape!

yeah, if it doesnt work then we all know the problem lies else where...

COsborne

damn, I thought this thread was about robot food...

reza

I used 330 Ohm 1/4 watt for the solenoid rackl, works fine, not even hot, well as hot as the engine bay can be

For the EGR feedback on Cali cars, you need to get relays. There is a thread about it somewhere in this 3rd gen forum too.

jwhite94RX7

Over last weekend I had occasion to disconnect my wastegate solenoid.

I unplugged the solenoid and turned on the ignition. Sure enough I got a check engine light. I displayed the ECU error code and it was for the wastegate solenoid.

I measured the resistance of the wastegate solenoid. It was just over 30 ohms. I inserted a 1000 ohm, 1/4 watt resistor into the connector in place of the solenoid and turned on the ignition. No check engine light. The resistor was not warm.



The EGR relay fix thread is here

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iTrader: (1)

Thanx a lot jwhite94RX7 for all your help.

I was not able to work on my car this weekend because of bad weather (no garage); hopefully this week I get a chance, here and there, to tinker with it. Thanx again for all your guys' help and I'll post my results as soon as I get it done.

BOTTLEFED

iTrader: (1)

Well its all back together after dodging a couple snowy days. I removed all the resistors I put in when I did my hose job/new wiring harness. These were 33ohm 1/2W. I did not remember but I had a straight (0ohm) wire connecting the 2 terminals of the air pump connector. I'm not sure why I did this at the time; I must have read somewhere that it was correct.

So I replaced all of them with 330ohm 1/2W resistors. I started the car and no smoking or frying resistors this time, SUCCESS! However the car still ran exactly the same . But at least it is fixed.

The funny thing is, the fried resistors all had reasonable resistance to them when I removed them. All read about 40-55ohms. In fact the EGR and switching solenoid resistors were not even melted a little. And the one that surprised me the most is that the air pump wire (no resistance) was perfectly fine too.

Thanx again to everyone that helped and I hope this thread will help others.