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Topic: Wacky pre OBD II antilock brake/transmission/cruise control mysteries (Read 291 times) previous topic - next topic
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Wacky pre OBD II antilock brake/transmission/cruise control mysteries
Perhaps someone has covered this but I thought I might share just in case. My tail lights on my 1990  were pretty rough so I thought I might save them away and install LED  super bright ones. They fit right in and really worked great. Then the weirdness started. Every time I used my turn signal the cruise control would drop out. It turns out the LEDs don't have enough resistance so the pre obd II sees it as a bulb failure and fail safes the the braking system including throwing an anti-lock brake fail warning. So, I went on Amazon and ordered some in line resistors and that problem went away. Since I was kind of focused on the braking/electrical issues I noticed another weird thing that probably had nothing to do with the new tail lights. I was trying to be safe by using my emergency flashers when I was climbing in the slow lane. When I had the flashers on my doghouse would get hot at the transmission area. So hot it would be uncomfortable near the passengers feet. No flashers - no overheating.  I read that pre obd II  Ford snow plow operators were having the same issue even though they were obviously operating during winter. What they determined was that the torque converter automatically unlocks if you touch the brakes.  In the early Fords they used the brake light circuit to signal the converter to unlock for a stop. They did not plan for people to drive around with their emergency blinkers on constantly.  So, every flash of the tail lights with the emergency blinkers was engaging and disengaging the torque converter. This, in the case of the snow plow drivers eventually toasted their transmissions. I quit using my emergency flashers climbing and have not had the hot doghouse syndrome since. Weird.
1990 26.5 MB
Re: Wacky pre OBD II antilock brake/transmission/cruise control mysteries
Reply #1 –
Quote from: Jagerbeast  - 
No flashers - no overheating.  I read that pre obd II  Ford snow plow operators were having the same issue even though they were obviously operating during winter. What they determined was that the torque converter automatically unlocks if you touch the brakes.  In the early Fords they used the brake light circuit to signal the converter to unlock for a stop. They did not plan for people to drive around with their emergency blinkers on constantly.  So, every flash of the tail lights with the emergency blinkers was engaging and disengaging the torque converter. This, in the case of the snow plow drivers eventually toasted their transmissions. I quit using my emergency flashers climbing and have not had the hot doghouse syndrome since. Weird.

Every brake light switch, on an OBDII vehicle, I have looked at has two sets of contacts, one to inform the computer that the brakes have been applied, the other to activate the brake lights. Your 1990 LD may have a single set of contacts so the switch powers the brake lights as well as informing the computer, causing the torque converter's clutch to unlock. This is done to allow the vehicle to come to a stop without stalling. Driving with the flashers on, pulling a long upgrade, could cook a transmission.

When installing LED tail lights, to prevent your vehicle's computer from indicating a burnt bulb, the fix is to use a CAN bus LED, one that has a built-in resistor.  The added on resistors are fine too, just a lot more work to install.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Wacky pre OBD II antilock brake/transmission/cruise control mysteries
Reply #2 –
Hi Jager. Those LED tail lights don't have as much current draw as light bulbs, so the resistors should be installed in parallel to provide some current draw to satisfy the cruise control. I've never heard of complications with the transmission, so as Larry said, the resistors must be necessary.  Thanks Larry for the CAN Buss idea.  RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Wacky pre OBD II antilock brake/transmission/cruise control mysteries
Reply #3 –
I have been considering changing out the headlights, running lights, brake lights, and turn signals to led units.  I have used the m4 product bulbs for the interior lights.  I am not familiar with the can buss type lights, but they do refer to them on the m4led website.    Does anyone have a recommendation for replacement leds manufacturers?
 
Re: Wacky pre OBD II antilock brake/transmission/cruise control mysteries
Reply #4 –

I was unable to find any tail lights with built in resistors that matched my old style round ones. Adding the resistors was no big deal because I had to totally rewire a complete rat's nest of previous repairs and modifications. It was a mess.  In retrospect, I probably would have just cleaned and rehabbed the old tail lights but even the sockets and inner light cavity were rusty and gnarly. The Chinese super bright tail lights are  fantastic now that all the mysteries are worked out and the back-up lights are like aircraft landing lights.   These are the resistors I used:                                                                                                  Amazon.com: 4Pcs Aaron 50W 6ohm Load Resistors - Fix LED Bulb Fast Hyper... 
The resistors have the downside of getting HOT if energized for long so that's another thing to consider. Don't want to start any unplanned campfires back there!  I think good working stock tail lights are less of a hassle and a better way to go unless your old LD originals are too far gone.

As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
1990 26.5 MB
Re: Wacky pre OBD II antilock brake/transmission/cruise control mysteries
Reply #5 –
Quote from: Jagerbeast  - 
The Chinese super bright tail lights are  fantastic now that all the mysteries are worked out and the back-up lights are like aircraft landing lights.  These are the resistors I used:                                                                                                  Amazon.com: 4Pcs Aaron 50W 6ohm Load Resistors - Fix LED Bulb Fast Hyper... 
The resistors have the downside of getting HOT if energized for long so that's another thing to consider. Don't want to start any unplanned campfires back there!  I think good working stock tail lights are less of a hassle and a better way to go unless your old LD originals are too far gone.

One cure for rapidly flashing tail lights, after changing to LEDs, is to switch the signal flasher to an electronic flasher that doesn't care what the tail light electrical load is.  This will eliminate the rapid flashing.
Search for electronic flasher, as opposed to an electro-mechanical flasher.
I believe your 1990 MB, on an E350 chassis, uses a two pole flasher.
Amazon.com: Bussmann 552 Electronic Flasher: Automotive

Larry

As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Wacky pre OBD II antilock brake/transmission/cruise control mysteries
Reply #6 –

I used these lights for my friends 2001 MB. Round LED Truck and Trailer Lights - 4” LED Brake/Turn/Tail Lights - 3-Pin...
In White for reverse lights. Without that rubber grommet: Round LED Truck and Trailer Lights - 4” LED Brake/Turn/Tail Lights - 3-Pin...
Stainless steel mounting flange: ST Series Stainless Steel Flange Mounts | Super Bright LEDs
3 pin connectors for all six lights:  Right Angle 3-Pin Plug for Trailer Lights and Truck Lights | Super Bright LEDs
Newer Ford Flasher, load independent, 3 pin 1999-2001 and more: Amazon.com: Grote 44892 3 Pin Flasher (North American (JSO) Pinout): Gateway

Larry's previous post  2 pin for older Fords was correct

And while you are at it, new license plate lights (2)  :  1-1/2” Round LED License Plate Light w/ 4 SMD LEDs w/ Chrome Housing | Super...

No need to waste power with those load resistors (fire hazards). Installation was awkward with the connectors that stuck out too far. Holes had to be cut in just the right places, sealed, and a closed cell polyethylene pad cut to fit behind the light to keep them pushed out against the flanges. (the new fixtures are thin). The MidBath had access from inside the storage compartments; other floor plans may be more difficult. I had trouble with the flanges not quite fitting inside the holes in the Fiberglas molded end cap, so I had to file down the edges of the trim rings to fit.   RonB

As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Wacky pre OBD II antilock brake/transmission/cruise control mysteries
Reply #7 –
I really like that chrome ring. I think I'll order those because AZ sun is not kind to rubber. Those lights look almost identical, including the connectors, to the ones I got from Amazon. I had the same problem of them being  a leeetle bit to large for the opening. I wasn't really having problems with rapid flashing, it was just that it would give me an abs warning light and also the cruise control would quit every time I used the turn signals.  Since I was rewiring everything I made sure to isolate the resistors near the underside of the bumper away from any wood. I definitely would not use them if they didn't take care of the  early obd computer issues.
1990 26.5 MB