Is this what a "ballast resistor" looks like?, I have little faith in the Radio Shack guy |
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Is this what a "ballast resistor" looks like?, I have little faith in the Radio Shack guy |
Porsche Rescue |
Sep 22 2008, 09:35 AM
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#1
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Saving and Enjoying Old Porsches Group: Members Posts: 2,978 Joined: 31-December 02 From: Bend, Oregon Member No.: 64 Region Association: None |
I'm trying to follow the suggestion of Brad Anders and others on this board. They recommend trying a 270 ohm ballast resistor in the the head temp sensor line as a way to richen the mixture as a fix for a poor cold running engine.
I asked for such a resistor and this is all the Radio Shack guy could provide. I had a choice between 220 ohms and 330 so I took 220. What concerns me is that the word "ballast" is nowhere on the item. Are these what I want or do I need keep looking? |
dr914@autoatlanta.com |
Sep 22 2008, 09:57 AM
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#2
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914 Guru Group: Members Posts: 7,858 Joined: 3-January 07 From: atlanta georgia Member No.: 7,418 Region Association: None |
the 270 ohm is available in factory form, but a 12 v radio shack 270 ohm would suffice placed in line with the head temp sensor. It was used to solve the hot running problems not cold running as the temp sensor at a full 2750 did fine to make the car run well cold. The residual 50 or so ohms the sensor provided hot was not quite enough on some of the high compression 2.0 models to give them the fatness of air to fuel ratio when hot so the factory then suggested and produced the resistor to cure this problem make the idle and whole range better (richer)
I would suggest that if you have a cold running problem the resistor is not the solution |
Spoke |
Sep 22 2008, 09:58 AM
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#3
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Jerry Group: Members Posts: 6,978 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
If you need a 270 ohm resistor and can only find 220 ohm, you can use 2 resistors in series to achieve 270 like 220 + 47 = 267 ohms.
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So.Cal.914 |
Sep 22 2008, 10:12 AM
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#4
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"...And it has a front trunk too." Group: Members Posts: 6,588 Joined: 15-February 04 From: Low Desert, CA./ Hills of N.J. Member No.: 1,658 Region Association: None |
QUOTE What concerns me is that the word "ballast" is nowhere on the item. Are these what I want or do I need keep looking? Yup they look like a ballast or load resistor. At that value they don't need to be very large. (IMG:style_emoticons/default/smile.gif) |
jasons |
Sep 22 2008, 10:28 AM
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#5
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Jackstand Extraordinaire Group: Members Posts: 2,002 Joined: 19-August 04 From: Scottsdale, AZ Member No.: 2,573 Region Association: None |
FWIW My car had a lean idle hunt when fully warm with the 270. I ended up using a variable resistor to dial out the hunt. 270 wasn't enough, I think I ended up in the mid 300's. Now it idles rock steady when warm.
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Porsche Rescue |
Sep 22 2008, 10:40 AM
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#6
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Saving and Enjoying Old Porsches Group: Members Posts: 2,978 Joined: 31-December 02 From: Bend, Oregon Member No.: 64 Region Association: None |
I have another thread on the board asking advice. My problem is: Car starts hard and requires lots of throttle action to keep it going. It coughs and sputters until it is fully warm (5 minutes or more on the road) and then runs perfectly, good idle, good acceleration, good power.
I replaced head temp sensor (not necessary, but did it anyway). It is correct for ECU according to Anders chart. ECU is correct for '70 1.7. AAR is open cold, closed hot. I did complete resistance check on all circuits from the ECU plug as per Anders and all were on spec. That led me to the resistor as a last resort. Other ideas welcome and appreciated. |
So.Cal.914 |
Sep 22 2008, 10:47 AM
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#7
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"...And it has a front trunk too." Group: Members Posts: 6,588 Joined: 15-February 04 From: Low Desert, CA./ Hills of N.J. Member No.: 1,658 Region Association: None |
FWIW My car had a lean idle hunt when fully warm with the 270. I ended up using a variable resistor to dial out the hunt. 270 wasn't enough, I think I ended up in the mid 300's. Now it idles rock steady when warm. Useing a potentiometer was a cleaver out of the box solution. Good thinking. (IMG:style_emoticons/default/smile.gif) |
jasons |
Sep 22 2008, 10:52 AM
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#8
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Jackstand Extraordinaire Group: Members Posts: 2,002 Joined: 19-August 04 From: Scottsdale, AZ Member No.: 2,573 Region Association: None |
Useing a potentiometer was a cleaver out of the box solution. Good thinking. (IMG:style_emoticons/default/smile.gif) I can't take credit, I think I read someone here did it. The lean idle hunt was driving me nuts and that fixed it. And, the car sails through emissions in AZ. |
r_towle |
Sep 22 2008, 12:04 PM
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#9
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Custom Member Group: Members Posts: 24,574 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
go back to radio shack.
Buy a variable rate potentiometer (a trun style volume knob) 0-1k ohms rated. Drive and turn, gently each time. Use an ohm meter to test the setting each time you turn it. Once you are happy, go back to radio shack and buy one or several resistors (like you show above) put them inline to add up to the same value the potentiometer was reading when you were happy. remove the potentiometer and replace it with the resistors. Rich |
davep |
Sep 22 2008, 12:54 PM
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#10
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914 Historian Group: Benefactors Posts: 5,143 Joined: 13-October 03 From: Burford, ON, N0E 1A0 Member No.: 1,244 Region Association: Canada |
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tod914 |
Sep 22 2008, 01:03 PM
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#11
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Advanced Member Group: Members Posts: 3,755 Joined: 19-January 03 From: Lincoln Park, NJ Member No.: 170 |
Please let me know what your low idle solution is. I'm very curious myself.
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orange914 |
Sep 23 2008, 01:04 AM
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#12
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http://5starmediaworks.com/index.html Group: Members Posts: 3,371 Joined: 26-March 05 From: Ceres, California Member No.: 3,818 Region Association: Northern California |
i've got the real deal (fact. 2.0/039 ecu resister) from a 73 2.0.
$20 +whatever shipping is to ya mike |
Bleyseng |
Sep 23 2008, 09:29 AM
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#13
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Aircooled Baby! Group: Members Posts: 13,034 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
I have another thread on the board asking advice. My problem is: Car starts hard and requires lots of throttle action to keep it going. It coughs and sputters until it is fully warm (5 minutes or more on the road) and then runs perfectly, good idle, good acceleration, good power. I replaced head temp sensor (not necessary, but did it anyway). It is correct for ECU according to Anders chart. ECU is correct for '70 1.7. AAR is open cold, closed hot. I did complete resistance check on all circuits from the ECU plug as per Anders and all were on spec. That led me to the resistor as a last resort. Other ideas welcome and appreciated. My thoughts on hard cold starting are that the grounds/wiring are corroded so getting the proper electricity to the coil/dizzy is the problem. You must have fuel and good spark. changing the cold mix is a bandaid fix until you find the root cause. Look for a vacuum leak too. Poor manifold gaskets act like this as they seal when the get warmed up. |
mike_the_man |
Sep 23 2008, 05:35 PM
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#14
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I like stuff! Group: Members Posts: 1,338 Joined: 11-June 03 From: Regina, Saskatchewan, Canada Member No.: 809 |
What about the Cold Start Injector? I can't remember how cold it has to be for the injector to fire, but could that contribute? The more I think about it, the less likely that is. The cold start injector only fires when the starting is cranking, correct? I guess that's not likely it. Sorry for the pointless post! (IMG:style_emoticons/default/smile.gif)
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Porsche Rescue |
Sep 23 2008, 06:04 PM
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#15
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Saving and Enjoying Old Porsches Group: Members Posts: 2,978 Joined: 31-December 02 From: Bend, Oregon Member No.: 64 Region Association: None |
Hi Mike. You're right, only when cranking and less than 50 degrees I think. Thanks for the help anyway. I will muddle on. I have a back-up ECU which I may try just for kicks.
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orange914 |
Sep 23 2008, 10:35 PM
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#16
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http://5starmediaworks.com/index.html Group: Members Posts: 3,371 Joined: 26-March 05 From: Ceres, California Member No.: 3,818 Region Association: Northern California |
i always thought the resister richened up the full rpm range. from there you could set idle as long as off idle up is good... no???
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Porsche Rescue |
Sep 24 2008, 10:14 AM
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#17
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Saving and Enjoying Old Porsches Group: Members Posts: 2,978 Joined: 31-December 02 From: Bend, Oregon Member No.: 64 Region Association: None |
D-jet guru Brad Anders suggests the resistor as a last resort solution to my type of problem. He agrees with you that it richens the mixture over the entire range. He suggests a switch in the cockpit to delete the resistor from the circuit when the car is warm.
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Porsche Rescue |
Sep 30 2008, 10:08 AM
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#18
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Saving and Enjoying Old Porsches Group: Members Posts: 2,978 Joined: 31-December 02 From: Bend, Oregon Member No.: 64 Region Association: None |
changing the cold mix is a bandaid fix until you find the root cause. Look for a vacuum leak too. Poor manifold gaskets act like this as they seal when the get warmed up. [/quote] Thanks Geoff. I have been too busy lately to work on the car, but I am anxious to check the torque on the intake manifolds. This engine has less than 5K on a DIY rebuild by the PO (pretty competent guy I think). I can't find any vacuum leaks in the ususal places. Is it also possible that the heads could be "loose" as well, self-sealing with expansion when hot? |
davep |
Sep 30 2008, 01:27 PM
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#19
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914 Historian Group: Benefactors Posts: 5,143 Joined: 13-October 03 From: Burford, ON, N0E 1A0 Member No.: 1,244 Region Association: Canada |
To answer your original question of "ballast resistor" it is more of an application thing. It is the use of a resistor in a ballast situation. That really does not mean much in this instance. What this resistor does is shift the operation range.
The resistors you have are fine, but I don't think they are suited to the wattage very well. See the photo in the link I provided above of an original resistor. To use what you have, put two in parallel, in series with two more in parallel; thus using four resistors and quadrupling the wattage while keeping the resistance the same. Do the same with some 47 ohm resistors, and add them in series to get very close to the 270 ohm original. |
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