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Thread: Does the Lambda relay always get hot?

  1. #11
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by DMC-81 View Post
    Dave, do you still offer the solid state Lambda relay? Does it still require the wiring change?
    I never made a Lambda relay for plug and play. It just takes one wire change to use the standard relay or one of my solid state standard relays.

    Yes the Lambda relay gets hot. Never knew why the design used a relay with two common output pins. I guess they were trying to fix an electrical noise problem. This was the second relay I replaced after the RPM relay because of the heating and the fact it is always on with the engine running.

    All you need to do is pull the center pin (red/purple wire) from the socket and connect that wire to the green/yellow wire on the pin above the center.
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  2. #12
    absotively posilutely bytes311's Avatar
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    Would the standard relay (with the wiring change) get just as hot as the Lambda relay?

  3. #13
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by bytes311 View Post
    Would the standard relay (with the wiring change) get just as hot as the Lambda relay?
    No. The heat is caused by the coil current in that relay. The standard relays use less current. I will look if I still have the OEM lambda relay and measure it.

    Edit:
    I found the OEM lambda relay. Tested and not as bad as I thought. I guess the smaller case makes it get hotter.
    61 ohms = 221 ma at 13.5 volts = 2.98 watts

    Standard relay
    86 ohms = 157 ma at 13.5 volts = 2.11 watts
    Last edited by Bitsyncmaster; 02-17-2019 at 07:43 PM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #14
    absotively posilutely bytes311's Avatar
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    Interesting! Thanks.

  5. #15
    Senior Member Chris 16409's Avatar
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    I rewired my Lambda relay socket according to Dave's directions and am using one of his standard solid state relays. I think it's a no brainer. The other plus is you eliminate the need to have a specialty Lambda relay. Any standard Bosch type relays will work to keep as spare.
    Chris Miles

    For Better or Worse I own a DeLorean!
    1983 Grey Manual, VIN #16409, Fresno, California

  6. #16
    absotively posilutely bytes311's Avatar
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    Quote Originally Posted by Chris 16409 View Post
    I rewired my Lambda relay socket according to Dave's directions and am using one of his standard solid state relays. I think it's a no brainer. The other plus is you eliminate the need to have a specialty Lambda relay. Any standard Bosch type relays will work to keep as spare.
    I agree, and it sounds simple enough.

  7. #17
    Senior Member Bitsyncmaster's Avatar
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    The second producer of heat in relays is the voltage drop due to the contact resistance and internal wiring of the load current. In the case of the lambda circuit I don't think there is much current and the OEM relay is rated at 15 amps on each output pin. Where that voltage drop is important is the higher current circuits like the fan relay. The fan relay load of 30 to 40 amps (OEM fans) can add another 5 watts or more of heating in the relay.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  8. #18
    Senior Member DMC-81's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    I never made a Lambda relay for plug and play. It just takes one wire change to use the standard relay or one of my solid state standard relays.

    Yes the Lambda relay gets hot. Never knew why the design used a relay with two common output pins. I guess they were trying to fix an electrical noise problem. This was the second relay I replaced after the RPM relay because of the heating and the fact it is always on with the engine running.

    All you need to do is pull the center pin (red/purple wire) from the socket and connect that wire to the green/yellow wire on the pin above the center.
    OK, cool. (Pun intended). I may do the simple wiring change and use a spare purple Bosch relay and see what kind of heating difference it makes. Then, I'll definitely opt for your solid state standard relays and keep my spare as the intended spare.

    I'm guessing that after the wiring change and by using the solid state relay the heating problem is mostly addressed?

    I just want to avoid cooking the plastic receptical and/or the wiring in the long term because of usage and warmer climate.

    Maybe then, I won't need an auxiliary fan to cool that area. The lambda relay got hot enough to heat the adjacent relays. Certainly not ideal.

    Quote Originally Posted by Chris 16409 View Post
    I rewired my Lambda relay socket according to Dave's directions and am using one of his standard solid state relays. I think it's a no brainer. The other plus is you eliminate the need to have a specialty Lambda relay. Any standard Bosch type relays will work to keep as spare.
    Great! Thanks for the review Chris.
    Dana

    1981 DeLorean DMC-12 (5 Speed, Gas Flap, Black Interior, Windshield Antenna, Dark Gray)
    Restored as "mostly correct, but with flaws corrected". Pictures and comments of my restoration are in the albums section on my profile.
    2006 Dodge Magnum R/T (D/D)
    2010 Camaro SS (Transformers Edition)

  9. #19
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by DMC-81 View Post
    OK, cool. (Pun intended)I'm guessing that after the wiring change and by using the solid state relay the heating problem is mostly addressed?
    My standard solid state relay draws 5 ma. so only 0.07 watts of power. And the voltage drop on the load is far less than any mechanical relays so it will stay at ambient temps for the lambda loads.

    I don't keep a lot of inventory of the headlight and standard (blower) relays because not many people get those. They use the same circuit boards as my fan relay with some component changes so there is no delayed operation. Headlight relays run the same power and load pins as the fan relay. The standard relays reverse the power and load pins internally in the relay. I wish all the relays would have used the same power and load pins.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #20
    Senior Member DMC-81's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    My standard solid state relay draws 5 ma. so only 0.07 watts of power. And the voltage drop on the load is far less than any mechanical relays so it will stay at ambient temps for the lambda loads.

    I don't keep a lot of inventory of the headlight and standard (blower) relays because not many people get those. They use the same circuit boards as my fan relay with some component changes so there is no delayed operation. Headlight relays run the same power and load pins as the fan relay. The standard relays reverse the power and load pins internally in the relay. I wish all the relays would have used the same power and load pins.
    Ok, perfect. I'll PM you when I'm ready for the relay.
    Dana

    1981 DeLorean DMC-12 (5 Speed, Gas Flap, Black Interior, Windshield Antenna, Dark Gray)
    Restored as "mostly correct, but with flaws corrected". Pictures and comments of my restoration are in the albums section on my profile.
    2006 Dodge Magnum R/T (D/D)
    2010 Camaro SS (Transformers Edition)

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