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I am simply saying that the wiring diagram shows them as being maintained, there is no latching circuit shown. Lotus admit that what goes on in the Switch Pack module is not shown. What is shown is that the parking light relay contact controls the two headlight relay coils, which is why the headlights can only be on with the parking lights.
 

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Dumb question. The heater bypass you are are describing is mounted up front, bypassing just the heater matrix, dropping the vent temps about 5 deg.

Looking at the diagram, and not the car, it seems like it would not be that difficult to move the bypass back to the engine bay, and not run hot water through the side pods and/or the heater core.

What am I overlooking?
 

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Dumb question. The heater bypass you are are describing is mounted up front, bypassing just the heater matrix, dropping the vent temps about 5 deg.

Looking at the diagram, and not the car, it seems like it would not be that difficult to move the bypass back to the engine bay, and not run hot water through the side pods and/or the heater core.

What am I overlooking?
The heater core acts as part of the "emergency overheat system". In simple terms, the car will pump fluid through the heater core at 230 F. - if the car is turned off (as I understand it). There are mentions of this behavior on the board. Maybe in this thread.
 

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There is one possible disadvantage of bypassing in the engine bay which has never been mentioned as far as I know. Because the heater, coolant and oil lines run parallel, very close to each other in the sills, we don't know how much heat would be transferred from the coolant and oil lines to the bypassed heater lines. There could still be significant heat ending up in the heater core even though it has been bypassed. Now, I really don't know if this would happen, but it is a possibility to be considered until it is proven otherwise. The other issue that has been mentioned is that if there is a switched bypass, cold coolant would suddenly flow into a hot engine, which is not a good idea. However, if the 3 lines transfer heat to each other, this is a moot point.
Dumb question. The heater bypass you are are describing is mounted up front, bypassing just the heater matrix, dropping the vent temps about 5 deg.

Looking at the diagram, and not the car, it seems like it would not be that difficult to move the bypass back to the engine bay, and not run hot water through the side pods and/or the heater core.

What am I overlooking?
 

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Discussion Starter · #246 ·
My opinion (FWIW) on the conduction of heat through the adjoining hoses in the sill:

I don't think the radiation of heat from the radiator and oil cooler lines to the bypassed heater lines would be an issue as the water is sitting still in the heater lines. I also don't believe there will be measurable performance difference in AC vent temps as the radiator and oil lines bring the bulk of the heat to the sills.

There is some length of heater line (both hard line and rubber hose) that are separate from the other lines as the tubing gets near the heater core (where it exits the sills and is routed to the core). It would take a very long time for the heat to migrate to the core itself without flow. If you think about it in older cars where the heater core was either blocked (heater off) or flowing (heater valve on), these didn't have a problem with heat being conducted in from the the engine through the return line, so I don't believe there is an issue here for our cars.


Concerning bypassing in the engine bay:
Two reasons I didn't go that way
1) cold water shock from the heater core when the bypass is disengaged (lessened by bypassing up front)
2) less change to heat circuit flow rate by routing up front. You can toast things or change the inputs to the ECU by varying flow rate for various inlets into the engine. There is a post eariler in the thread about someone causing damage in a Ford-engined race car (not a Lotus) by eliminating a heater core with no restrictor.

I'm not sure either of these issues is a problem, in fact I seriously doubt there is a problem with the rear bypass at all. I was just unwilling to take the chance with my and other people's cars. You only install the bypass once and the delta in work from front to rear just wasn't worth the small savings in time to me.

If you wanted to do a engine bay bypass, I would use a restrictor in the bypass coolant line. I actually researched and bought one from a GM car back during the kit development days. I can do some testing to determine the restrictor size required if there is serious interest.

my .02
 

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Measure twice, cut once

Here's some free advice to anyone contemplating this procedure:

Pay particular attention to the passage in the instructions which stresses the importance of positioning the bypass valve as far to the passenger-side as possible.

Somehow, I completely forgot this part, and also forgot about the corrugated air tube which connects the evaporator to the cabin ventilation system :confused:. Imagine the "oh ****" moment whereupon completing installation of the valve, I realized I'd placed it directly above the opening in the evaporator and that the corrugated pipe could no longer be installed -eek-

In the end, I'd turned a two hour job into a two day job. I had to replace the input and output heater core hoses- this isn't someone you want to do. While not technically difficult, the spaces involved are so tight that there were at least a couple moments where I was sure I was going to have the whole thing flat-bedded to my dealer.

In the end, I got it done. Since I'd replaced the heater hoses, I had more latitude with respect to placement. I installed the valve on the far right (driver's side, near the vacuume reservoir) where there exists lots of space.

I'll test the effectiveness of the change later today.
 

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Holy Cow! It works!
I performed the bypass mod along with removal of the driver's-side footwell vent cover.
I drove 70 miles today in combined highway and city stop and go traffic. Humidity was ~100%. 40 miles of sunshine, 30 miles of thunderstorms, high 80's.
Half way through, I left the car parked in the hot sun for about 30 min.
The result (and many of you won't believe this): once it began to rain I had to turn the fan to "1" (too cold on 3), and even so the rear window fogged up- on the OUTSIDE!
The ride was cool the entire trip- the AC seemed (sorry, no thermometer with me) to retain its original cold temp the entire trip. In addition, during stops the temp likewise seemed rock solid.
Wish I had done this three years ago!
 

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I cannot find that EGR valve anywhere! Anyone have a part number or alternative?
 

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Discussion Starter · #251 ·
Source for Valve

Hi There!

It's actually a Heater Bypass valve, not an EGR. It was on late 90s Ford Ranger trucks (when they ask for engine size, just go with smallest). You should be able to pick it up at Advance, Autozone, or the like.

BTW - If anyone wants a kit, I still have one left I was holding for someone.:shrug:
$125.

Thanks!
Tony
 

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I found the heater bypass valve.

I'm looking for the vacuum switch. the one listed for the 1990 astro van.
 

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Discussion Starter · #253 ·
EGR Vacuum Solenoid

Sorry about that! Make sure your looking for the EGR vacuum solenoid, not the EGR valve itself.

RockAuto has it.

Airtex part #2F1120 $15.70
Standard Motor Parts makes it as well.

I've always been able to buy this over the couter at the chain stores. They usually only keep one in stock however....Good Luck!!

FYI - Here's some other applications for that solenoid (as listed by RockAuto):

CHEVROLET ASTRO (1987 - 1991)
CHEVROLET BLAZER (1987 - 1994)
CHEVROLET C1500 PICKUP (1988 - 1995)
CHEVROLET C1500 SUBURBAN (1992 - 1995)
CHEVROLET C2500 PICKUP (1988 - 1995)
CHEVROLET C2500 SUBURBAN (1992 - 1995)
CHEVROLET C3500 PICKUP (1988 - 1995)
CHEVROLET G10 SPORTVAN (1987 - 1991)
CHEVROLET G10 VAN (1987 - 1991)
CHEVROLET G20 SPORTVAN (1987 - 1991)
CHEVROLET G20 VAN (1987 - 1991)
CHEVROLET G30 VAN (1987 - 1991)
CHEVROLET K1500 PICKUP (1988 - 1995)
CHEVROLET K1500 SUBURBAN (1992 - 1995)
CHEVROLET K2500 PICKUP (1988 - 1995)
CHEVROLET K2500 SUBURBAN (1992 - 1995)
CHEVROLET K3500 PICKUP (1988 - 1995)
CHEVROLET P20 VAN 1987
CHEVROLET P30 VAN 1987
CHEVROLET R10 PICKUP 1987
CHEVROLET R10 SUBURBAN (1987 - 1988)
CHEVROLET R1500 SUBURBAN (1989 - 1991)
CHEVROLET R20 PICKUP (1987 - 1988)
CHEVROLET R20 SUBURBAN (1987 - 1988)
CHEVROLET R2500 SUBURBAN (1989 - 1991)
CHEVROLET R30 PICKUP (1987 - 1988)
CHEVROLET R3500 PICKUP (1989 - 1991)
CHEVROLET S10 BLAZER (1987 - 1988)
CHEVROLET S10 PICKUP (1987 - 1990)
CHEVROLET TAHOE 1995
CHEVROLET V10 PICKUP 1987
CHEVROLET V10 SUBURBAN (1987 - 1988)
CHEVROLET V1500 SUBURBAN (1989 - 1991)
CHEVROLET V20 PICKUP 1987
CHEVROLET V20 SUBURBAN (1987 - 1988)
CHEVROLET V2500 SUBURBAN (1989 - 1991)
CHEVROLET V30 PICKUP (1987 - 1988)
CHEVROLET V3500 PICKUP (1989 - 1991)
GMC C1500 PICKUP 1988
GMC C1500 PICKUP SIERRA (1989 - 1995)
GMC C1500 PICKUP SIERRA XC (1989 - 1995)
GMC C1500 SUBURBAN (1992 - 1995)
GMC C2500 PICKUP 1988
GMC C2500 PICKUP SIERRA (1989 - 1995)
GMC C2500 PICKUP SIERRA XC (1989 - 1995)
GMC C2500 SUBURBAN (1992 - 1995)
GMC C3500 PICKUP 1988
GMC C3500 PICKUP SIERRA (1989 - 1995)
GMC C3500 PICKUP SIERRA XC (1989 - 1995)
GMC G1500 VAN RALLY (1987 - 1991)
GMC G1500 VANDURA (1987 - 1991)
GMC G2500 VAN RALLY (1987 - 1991)
GMC G2500 VANDURA (1987 - 1991)
GMC G3500 VANDURA (1987 - 1991)
GMC JIMMY (1987 - 1991)
GMC K1500 PICKUP 1988
GMC K1500 PICKUP SIERRA (1989 - 1995)
GMC K1500 PICKUP SIERRA XC (1989 - 1995)
GMC K1500 SUBURBAN (1992 - 1995)
GMC K2500 PICKUP 1988
GMC K2500 PICKUP SIERRA (1989 - 1995)
GMC K2500 PICKUP SIERRA XC (1989 - 1995)
GMC K2500 SUBURBAN (1992 - 1995)
GMC K3500 PICKUP 1988
GMC K3500 PICKUP SIERRA (1989 - 1995)
GMC K3500 PICKUP SIERRA XC (1989 - 1995)
GMC P3500 VAN 1987
GMC R1500 PICKUP 1987
GMC R1500 SUBURBAN (1987 - 1991)
GMC R2500 PICKUP (1987 - 1989)
GMC R2500 SUBURBAN (1987 - 1991)
GMC R3500 PICKUP (1987 - 1991)
GMC S15 JIMMY (1987 - 1988)
GMC S15 PICKUP (1987 - 1990)
GMC SAFARI (1987 - 1991)
GMC SAFARI XT (1990 - 1991)
GMC V1500 PICKUP 1987
GMC V1500 SUBURBAN (1987 - 1991)
GMC V2500 PICKUP 1987
GMC V2500 SUBURBAN (1987 - 1991)
GMC V3500 PICKUP (1987 - 1991)
GMC YUKON (1992 - 1995)
 

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awsome. I'll go pick them up today.
 

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Discussion Starter · #255 ·
One more bypass kit available

Folx,
I have one last kit for sale (NOS):). $125 with standard switch or pot
 

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FYI - Here's some other applications for that solenoid (as listed by RockAuto):
So basically, every Chevy/GMC "truck" made in the last 20 years... :D
 

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Discussion Starter · #257 ·
Yep,

I'd consider this part "readily available":)
 

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Discussion Starter · #259 ·
Kit is gone!

Last kit sold. I can still get the potentiometers if someone needs them.
Thanks:clap:
 

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THANKS, TONY!!!!!

Tony,

A big thanks from the Lotus community for all your efforts!!!!

:up::up::up:
 
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