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Up-fixin Electric Quirks on 1986-88 Esprits w/ Bosch CIS K-Jetronic Injection
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24 ohms, connected to ECU pin 12 which goes to the LOW TEMP sensor. Pin 12 is grounded by the sensor until temp is greater than 25C which enables the choke function equivalent in the ECU
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Esprit Headlight Lift Module Failure
Preventing headlight lift motor current sensing module failure.
There are two MOSFET-s, which often overheat and fail.
As a countermeasure, add heat sinks to both. Apply heat conductive white goo before tightening the screws.
Add two strips of closed cell foam over the terminal blades to seal off the box against water intrusion.
??? Anyone has a x-reference for this component???
I think it may have been used on GM cars in the 80-s.
.
Preventing headlight lift motor current sensing module failure.
There are two MOSFET-s, which often overheat and fail.
As a countermeasure, add heat sinks to both. Apply heat conductive white goo before tightening the screws.
Add two strips of closed cell foam over the terminal blades to seal off the box against water intrusion.
??? Anyone has a x-reference for this component???
I think it may have been used on GM cars in the 80-s.
.
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Hey! Can't you read? :facepalm
The sticker in your photo says "REPLACE DO NOT REPAIR" :no:
rotfl rotfl rotfl
More seriously:
(Yes, I DO see water stains in the first pic)
You should post this in a separate Topic since it applies to ALL Stevens Esprits, BTW.)
The sticker in your photo says "REPLACE DO NOT REPAIR" :no:
rotfl rotfl rotfl
More seriously:
Where is this located again...and why would it get wet? :scratchhead:
(Yes, I DO see water stains in the first pic)
You should post this in a separate Topic since it applies to ALL Stevens Esprits, BTW.)
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1,338 Posts
I also have a spare (that's not for saleThose are MOSFETs, not thyristors. I have a spare good module if anyone needs one, to replace, not repair
) but note that its the same module fitted to the M100 Elan and over on the LEC forum somewhere it was discovered that this was fitted to several GM cars of the period (85 to 95) so they are still available, should you want to replace not repair
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Here ya go, NOTE: the sunbird/Fiero modules are NOT the ones you want, you want the 92/93 Firebird modules:So...tell me where the module located in the in M100, too (in case I want to grab it while no one is looking). >
JUST KIDDING... (maybe)
Lotus Elan Central
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3,248 Posts
Blinking Econ Light = Speed Sensing Module failure
Thank you Van for this insightful investigation and a repair procedure.
Fri Mar 17, 2017 7:36 am (PDT) .
Posted by:
"Van Overhouse" van_overhouse
For 86-88 MY cars with the Bosch CIS system the green ECON light should come on steady while off throttle and in overrun condition. In two cases now I've seen that the light blinks rather than remain on. I traced this back to a bad "Speed Sensing Module" which I replaced the first time. Now that I've seen the problem a second time I decided to try and fix the Module rather than buying a new one. The first step was to do some reverse engineering and generate a schematic for the Module. I've posted the schematic at Turbo List files/tech/electric .
What I found was that either the Module design has an error or the Lotus application is incorrect. Within the module there is a 750 ohm 1/4W resistor connected between pin #15 (V+ from RPM Relay) and terminal #31b going to the Thermal Time Switch. During warm up, terminal #31b is grounded by the Thermal Time Switch until the water temperature reaches 35C. During this period the 750 resistor has 14.5V across it which generates (14.5*14.5/750= 0.3W) watts which is greater than the resistor specification allows. Once up to temperature the ground is removed and the power drops to about .13 watts. This extra stress on the resistor eventually causes it to fail.
In addition, the 750 ohms is too large a resistor and current flowing through it and out to the thermal time switch is causing too much voltage drop. The voltage at the node with the 750 ohm (?), 27K and ITT diode is too low to turn on the BC547 transistor. Making the resistor smaller will raise this voltage to the acceptable level.
?What would be the smallest 1/4W resistor you could use to replace the 750 ohm (R= E*E/P).
So if you put in a 1W resistor that would be 316 ohms you're be fine.
I'd replace it with a 330 ohm, at least 1/2 W resistor.
After replacing the resistor, the relay module should not fail again.
If you have a blinking Econ light and want to quickly test if you have the same problem just disconnect the Thermal Time Switch connector once the engine is up to temperature. If the Econ light no longer blinks you most likely have the same problem. If you do have this problem you should fix it as it is also pulsing the air bypass valve which will wear it out prematurely. Don't throw away your old Speed Sensing Modules they are repairable and we may need them some day.
Module: It's the one with the black base and you should see the Bosch part number 0 280 230 103 on the case [back wall, above the coil]. I didn't replace the Ecap on the PC board since I tested the module on the bench. Probably should have replaced it with 35V or 50V cap. Hopefully, it doesn't come back to bite me.
After thinking about the error I believe it must be the Lotus application of the module that is incorrect. Also, I believe that pretty much every Lotus module out there has a "750 resistor problem".
The original resistor looks to be a ceramic thin film resistor and the failure mechanism for this type of resistor is when it overheats is for the resistance to increase (if it doesn't fail outright like a fuse).
Once the resistance becomes high enough, it will no longer overheat. In some cases the higher resistance is not sufficient to cause the circuit not to work. In other cases it is too high and the module fails with the blinking ECON light syndrome.
Thank you Van for this insightful investigation and a repair procedure.
Fri Mar 17, 2017 7:36 am (PDT) .
Posted by:
"Van Overhouse" van_overhouse
For 86-88 MY cars with the Bosch CIS system the green ECON light should come on steady while off throttle and in overrun condition. In two cases now I've seen that the light blinks rather than remain on. I traced this back to a bad "Speed Sensing Module" which I replaced the first time. Now that I've seen the problem a second time I decided to try and fix the Module rather than buying a new one. The first step was to do some reverse engineering and generate a schematic for the Module. I've posted the schematic at Turbo List files/tech/electric .
What I found was that either the Module design has an error or the Lotus application is incorrect. Within the module there is a 750 ohm 1/4W resistor connected between pin #15 (V+ from RPM Relay) and terminal #31b going to the Thermal Time Switch. During warm up, terminal #31b is grounded by the Thermal Time Switch until the water temperature reaches 35C. During this period the 750 resistor has 14.5V across it which generates (14.5*14.5/750= 0.3W) watts which is greater than the resistor specification allows. Once up to temperature the ground is removed and the power drops to about .13 watts. This extra stress on the resistor eventually causes it to fail.
In addition, the 750 ohms is too large a resistor and current flowing through it and out to the thermal time switch is causing too much voltage drop. The voltage at the node with the 750 ohm (?), 27K and ITT diode is too low to turn on the BC547 transistor. Making the resistor smaller will raise this voltage to the acceptable level.
?What would be the smallest 1/4W resistor you could use to replace the 750 ohm (R= E*E/P).
So if you put in a 1W resistor that would be 316 ohms you're be fine.
I'd replace it with a 330 ohm, at least 1/2 W resistor.
After replacing the resistor, the relay module should not fail again.
If you have a blinking Econ light and want to quickly test if you have the same problem just disconnect the Thermal Time Switch connector once the engine is up to temperature. If the Econ light no longer blinks you most likely have the same problem. If you do have this problem you should fix it as it is also pulsing the air bypass valve which will wear it out prematurely. Don't throw away your old Speed Sensing Modules they are repairable and we may need them some day.
Module: It's the one with the black base and you should see the Bosch part number 0 280 230 103 on the case [back wall, above the coil]. I didn't replace the Ecap on the PC board since I tested the module on the bench. Probably should have replaced it with 35V or 50V cap. Hopefully, it doesn't come back to bite me.
After thinking about the error I believe it must be the Lotus application of the module that is incorrect. Also, I believe that pretty much every Lotus module out there has a "750 resistor problem".
The original resistor looks to be a ceramic thin film resistor and the failure mechanism for this type of resistor is when it overheats is for the resistance to increase (if it doesn't fail outright like a fuse).
Once the resistance becomes high enough, it will no longer overheat. In some cases the higher resistance is not sufficient to cause the circuit not to work. In other cases it is too high and the module fails with the blinking ECON light syndrome.
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The other GM modules do NOT work in the Esprit. The look identical and they plug in but they will not function properly. You're throwing money away if you buy one. I have been down this path and tested out a bunch of them. If you need a module contact Sanj. He can repair them if the MOSFET is bad.
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330 Ohm, 1 W resistor installed
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Overspeed Module Problem
Hi John:
Yes, I believe there is an error in the [Overspeed Module] design. There is a "B" revision (B082M6374) which may correct the problem but I'm not sure since I dissected the "A" rev part.
The failure symptom is after driving the car and you park it hot and leave it for 10-20 minutes it will not start. If you wait for an hour or so and it cools down it will start.
The problem, I believe, is that humidity is collecting around R6 (2.2Meg ohms) and lowering its resistance. The specification for the TC4538 says that the maximum resistor value allowed is 1Meg (!). If you look at the bottom of the schematics you can see a note where I changed the value of R6 to 220K ohms and C4 to 1uf. Other values which result in the same time constant (R6 X C4=220ms) would also be OK. After replacing these parts I've never had the problem reoccur.
Van Overhouse
Hi John:
Yes, I believe there is an error in the [Overspeed Module] design. There is a "B" revision (B082M6374) which may correct the problem but I'm not sure since I dissected the "A" rev part.
The failure symptom is after driving the car and you park it hot and leave it for 10-20 minutes it will not start. If you wait for an hour or so and it cools down it will start.
The problem, I believe, is that humidity is collecting around R6 (2.2Meg ohms) and lowering its resistance. The specification for the TC4538 says that the maximum resistor value allowed is 1Meg (!). If you look at the bottom of the schematics you can see a note where I changed the value of R6 to 220K ohms and C4 to 1uf. Other values which result in the same time constant (R6 X C4=220ms) would also be OK. After replacing these parts I've never had the problem reoccur.
Van Overhouse
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C4 and R6 are soldered directly to the pins of the IC! Yikes!
If you try to de-solder them, you're may overheat the IC chip.
Solution:
Crush C4 to expose its conductors sticking up above the board and solder the new cap to them. Resistor can be replaced in the same way.
Note: Tantalum caps have polarity! The + leg is always longer.
"While you're there", replace the 22uF electrolytic cap (large, blue) with a fresh 50V rated part. After 15 years they can fail any minute and their 16V rating may cause a bad day for you.
If you try to de-solder them, you're may overheat the IC chip.
Solution:
Crush C4 to expose its conductors sticking up above the board and solder the new cap to them. Resistor can be replaced in the same way.
Note: Tantalum caps have polarity! The + leg is always longer.
"While you're there", replace the 22uF electrolytic cap (large, blue) with a fresh 50V rated part. After 15 years they can fail any minute and their 16V rating may cause a bad day for you.
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Re: posting #5 of this thread.
If you need a help with yours, talk to Sanj on this forum.
This mod applies to ALL Esprits/all model years.
If you need a help with yours, talk to Sanj on this forum.
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For cleaning contacts, switches, terminals use DeOxit.
Apply DeOxit sparingly to the contacts on each wafer and then switch the control through every position several times.
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3,248 Posts
ALUMINUM ELECTROLYTIC CAPACITOR FAILURES
There are electrolytic capacitors in every Engine Management Module/PC board on our 86, 87 and 88 Esprits.
Like all components, electrolytic capacitors eventually do wear-out. Unfortunately, their lives are relatively short (~15 years) compared to other components in the system. Capacitor is essentially an electro-chemical device, hence increased temperatures accelerate the chemical reaction rates within the capacitor. Environmental factors include temperature, humidity, atmospheric pressure and vibration. Electrical factors include operating voltage, ripple current and charge-discharge duty cycle. Among these factors, temperature (ambient temperature and internal heating due to ripple current) is the most critical to the life of aluminum electrolytic capacitors.
OEM capacitors are rated 16V, which (in real life) is inadequate.
Continuous application of excessive operating voltages will rapidly increase the leakage current. Internal heating and gas generation caused by increased leakage current may destroy the capacitor.
Other modules also have these dreadful caps inside. Replace them all.
The old OEM cap(s) should be replaced by modern electrolytic capacitors (rated 50V) of the same capacitance value.
![Circuit component Hardware programmer Electronic component Microcontroller Passive circuit component]()
Fuel By-pass Speed Sensing Module Relay
![Circuit component Passive circuit component Electronic component Hardware programmer Electronic device]()
RPM Module Relay
![Circuit component Passive circuit component Computer hardware Electronic component Audio equipment]()
There are electrolytic capacitors in every Engine Management Module/PC board on our 86, 87 and 88 Esprits.
Like all components, electrolytic capacitors eventually do wear-out. Unfortunately, their lives are relatively short (~15 years) compared to other components in the system. Capacitor is essentially an electro-chemical device, hence increased temperatures accelerate the chemical reaction rates within the capacitor. Environmental factors include temperature, humidity, atmospheric pressure and vibration. Electrical factors include operating voltage, ripple current and charge-discharge duty cycle. Among these factors, temperature (ambient temperature and internal heating due to ripple current) is the most critical to the life of aluminum electrolytic capacitors.
OEM capacitors are rated 16V, which (in real life) is inadequate.
Continuous application of excessive operating voltages will rapidly increase the leakage current. Internal heating and gas generation caused by increased leakage current may destroy the capacitor.
Other modules also have these dreadful caps inside. Replace them all.
The old OEM cap(s) should be replaced by modern electrolytic capacitors (rated 50V) of the same capacitance value.
Fuel By-pass Speed Sensing Module Relay
RPM Module Relay
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