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EGR Temp Switch - Can't find??

ltmark

Member
Joined
Jan 20, 2010
Messages
13
Location
Diamond Bar, ca.
Corvette
1985 coupe, bright red
My EGR temp switch is bad. Rather than closing after the egr heats up, it is closed (or grounded) ALL THE TIME. Thus, I get a code 32. I can't find one any place...even the large Vette Sites? It is simply a small sensor that screws into the EGR valve (beneath the plenum) and then goes to the ECM.

Is there any other sensor that "closes permanently" after the engine heats up that I could splice in to? That is the final problem that I am having before re-registering my '85 after a few years off the road. I'm in Ca. so it has to pass smog! I thought of putting in a toggle switch so I could just flip it after the engine warms up so the EGR system will work properly, but I hate to mickey-mouse it to that point!.

The original temp switch center sensor will "screw-in", but it either remains open or closed depending how far I turn it in. It was originally set and then some sort of glue applied to keep it from screwing in or out.

Thanx for any help!
 
Sounded good! No Luck

I ordered the EGR temp switch and low an behold, they refunded the money and said "oops", we actually don't have any. For the last two days, I've done nothing but call every auto supplier out there. A lot of them have them on the site, but no one actually has the switch.

I'm hoping someone can come up with an intelligent work-a-round!

Here is the issue. The EGR temp switch is a simple open or closed switch. It screws into the EGR housing and after the car is started and warmed up (supposedly 176 degrees), it closes (thereby going to ground) and the ECM reads that signal along with 4 others in order to allow EGR into the intake manifold to cool the combustion for emission purposes. When it is either closed on startup or open when warm, code 32 is set!

Idea 1. put a toggle switch in the dash and simply flip it when the car is warm! would work but really Mickey Mouse!

Idea 2. buy a Aux fan temp switch (180 degree) just like the Aux. temp switch by # 8 cyl) and fashion a bracket that will hold it against the block. Then, when the block heats up, the switch goes to ground and all is well! Not nearly as Mickey Mouse as #1, but not real great either!

There are no other sensors that are simple on/off on the car. All are thermistors, etc.

Any thoughts out there??

Thanx
 
Did you check with JD in Bellflower?
 
Try Vette2Vette

Telephone:
1-815-673-6200

Contact Email: parts@vette2vette.net

FROM THE WEBSITE..........
************************************************
We have over 200,000 great used Corvette parts in stock in our indoor inventory, with additional Corvettes and parts arriving all the time. Our prices are fair and simple and we have a money back guarantee if you are not delighted. We specialize in dismantling 1984-2004 year Chevrolet Corvettes and also offer new parts shipped to your door at wholesale prices.
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I've never used them, and don't even know if they're still in business, but it can't hurt to try........
Ya just never know................
Andy :w
 
Itmark -

Did you figure out a solution for this switch? I have also been thinking about making a work-around fix.
 
The EGR switch is a mechanical bi-metal device. There is a thin strip of metal inside that changes its shape in relation to temperature. When the EGR opens, the hot gases heat up the sensor and it makes a ground connection.

Technically, a substitute device could be made from a thermistor with basic circuitry and the ECM would not know the difference. The circuit could use a simple op-amp configured as a voltage comparator. Your reference voltage would be 5VDC, then the thermistor would be the variable voltage (when set correctly) to activate the "EGR" at the right temperature. You can use the old switch housing to mount the thermistor in.

I've been meaning to make a circuit and tinker with it to dial it in, but have had no time lately. I estimate the cost to be about $10 in parts from RS.

I have an '87 Camaro that uses this type of EGR switch and bought one at CarQuest a couple years ago before they got scarce.
 
The EGR switch is a mechanical bi-metal device. There is a thin strip of metal inside that changes its shape in relation to temperature. When the EGR opens, the hot gases heat up the sensor and it makes a ground connection.

Technically, a substitute device could be made from a thermistor with basic circuitry and the ECM would not know the difference. The circuit could use a simple op-amp configured as a voltage comparator. Your reference voltage would be 5VDC, then the thermistor would be the variable voltage (when set correctly) to activate the "EGR" at the right temperature. You can use the old switch housing to mount the thermistor in.

I've been meaning to make a circuit and tinker with it to dial it in, but have had no time lately. I estimate the cost to be about $10 in parts from RS.

I have an '87 Camaro that uses this type of EGR switch and bought one at CarQuest a couple years ago before they got scarce.

So, the temp switch doesn't affect the operation of the EGR valve?

My EGR was bad, but never got a code 32. So, thought of pulling the switch to test it. But looks like I shouldn't bother.
 
Not sure if this is the correct item but will toss it out there. Rock Auto RockAuto Auto Parts
lists an EGR time delay switch, search under 85 Corvette, then use the Electrical-Switch & Relay tab. Hope that helps.
 
I see two options if you can't find the exact replacement part.
1. Build a custom switch using a fan switch as suggested above. I've seen smaller sized fan switches with pigtails at my local auto parts store. Then it is a trip to the hardware store to find the right fittings.
2. Use an adjustable thermocouple fan switch that has a sensor probe (around 1" long and has a stiff lead wire) that you could attach to the external EGR tube using a worm gear clamp. This option provides some adjustment on your part to find the right setting. I used one of these adjustable fan switches for a different purpose and found it pretty accurate when attached to a coolant inlet pipe then wrapped with high temperature foil tape.
I prefer option 1. Looks like a great Saturday morning project.
 
Itmark -

Did you figure out a solution for this switch? I have also been thinking about making a work-around fix.

You've actually confirmed that the SWITCH is bad? That the circuit stays OPEN (or CLOSED)???

If it stays OPEN, have you tested for a break in the lines - TO and FROM the switch?
 
So, the temp switch doesn't affect the operation of the EGR valve?.
Does not affect EGR operation

EGR temp switch in question only reports to the ECM that the EGR valve is operating correctly by sensing that Exh gas is flowing to the intake.
 
So, the temp switch doesn't affect the operation of the EGR valve?

My EGR was bad, but never got a code 32. So, thought of pulling the switch to test it. But looks like I shouldn't bother.
If the EGR temp. switch is not working correctly, this event will trigger the ECM code. If the actual EGR valve is not working, then the ECM WILL NOT know this, with the exception of possible detonation, which the ECM will detect, and retard timing.

The ECM is not smart enough to know these two events are related.
 
If the EGR temp. switch is not working correctly, this event will trigger the ECM code. If the actual EGR valve is not working, then the ECM WILL NOT know this, with the exception of possible detonation, which the ECM will detect, and retard timing.

The ECM is not smart enough to know these two events are related.
The purpose of the EGR switch is to alert the ECM that the EGR system is not working properly. If an EGR port is not flowing exhaust gas properly (defective EGR, plugged passage ...), then the external EGR pipe will not reach a hot enough temp to close the EGR switch.
 
The purpose of the EGR switch is to alert the ECM that the EGR system is not working properly. If an EGR port is not flowing exhaust gas properly (defective EGR, plugged passage ...), then the external EGR pipe will not reach a hot enough temp to close the EGR switch.
I concur.

When I was writing my post I was thinking in my head that if the EGR was stuck open, then the computer would not know this.

Thanks for clarifying. My brain was working faster than my fingers...
 
The purpose of the EGR switch is to alert the ECM that the EGR system is not working properly. If an EGR port is not flowing exhaust gas properly (defective EGR, plugged passage ...), then the external EGR pipe will not reach a hot enough temp to close the EGR switch.

My EGR tested bad as I couldn't pull a vacuum. But I never got a code 32 for some reason.
 
If the EGR temp. switch is not working correctly, this event will trigger the ECM code. If the actual EGR valve is not working, then the ECM WILL NOT know this, with the exception of possible detonation, which the ECM will detect, and retard timing.

The ECM is not smart enough to know these two events are related.

In my scans, I get knock counts on acceleration. I can hear stuff when accelerating sometimes that I'd guess is knock. I replaced the EGR since it was bad, and went to 93 octane instead of 87. But still get the knock. I've read bad plug wires can cause knock. I put on a universal set of Taylor wires, which I've read some bad reviews on. I may change the plug wires to see if that does anything.

I did an EGR test where I pulled a 10" vacuum or so on the EGR valve. And I start the car, and the vacuum goes to 0. Which I believe it is supposed to do that. As I was wanting to check and make sure the passage ways were clear. But I tried another test of trying to pull vacuum on the EGR while the car was running to see if I could get it to stumble to verify exhaust gas is flowing. But I couldn't pull a vacuum on the EGR, and I didn't notice any change in the engine. I think you should be able to pull a vacuum on the EGR valve with the car running. On another old GM car with an L03 TBI engine, I could pull a vacuum on the EGR valve while the car was running to get it to stumble.
 
The EGR design is a negative pressure EGR valve. I was having intermittent pinging. After reading a post from a L81 owner, it provided some hints that maybe my EGR was not 100%. The net of my labor and testing was that the EGR was acting "lazy". Worked just enough not to trigger any codes, but not enough to flow the proper volume of exhaust gas into the heads to cool them. Popped in an exact AC Delco EGR and the pinging stopped. Idle quality should suffer if you force open the EGR valve at idle. This is easy test to see if the EGR ports are plugged.
 

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