TahoeFerrari Posted July 11, 2005 Share Posted July 11, 2005 Car is '87 3-door EA82 spfi. Mechanical speedometer reads high (pegs) as soon as I get to about 10mph! Odometer and trip counter update correctly. I've not done anything with it yet. I'd like to know what I'm dealing with before tearing the instrument panel out. Does anyone know what causes this and how to fix? Or do I need another instrument cluster?? Quote Link to comment Share on other sites More sharing options...
TahoeFerrari Posted July 12, 2005 Author Share Posted July 12, 2005 push Quote Link to comment Share on other sites More sharing options...
All_talk Posted July 12, 2005 Share Posted July 12, 2005 The EA82 cars seem to have some issues with slow reacting and sticking speed-O heads. My RX is a bit slow, I haven't tore into it yet to see if there is a fix, nor have I heard of anyone who has. Replacment with a know good/low mile head might be best, for now I drive by the tach most of the time. Gary Quote Link to comment Share on other sites More sharing options...
TahoeFerrari Posted July 23, 2005 Author Share Posted July 23, 2005 I finally bit the bullet and took the instrument cluster apart to get to the speedo. Found the cause of the problem. Some grease from the speedo cable had worked its way up into the speedo head. The grease had filled the air gap between the spinning armature (attached to the cable) and rotor (attached to the speed indicating needle) and so the grease was acting as a torque transmission medium and actually "dragging" the rotor to cause the high readings (I think that normally the spinning armature moves the rotor across the airgap by magnetism). Kind of hard to explain unless you've seen it, but cleaning out the grease corrected the problem. Not a repair for the faint at heart - you've got to disassemble the speedo to do this!! It took me two tries and 4-5 hours to get it right. But it would have taken me about that much time to drive 80 miles round trip to my nearest JY, plus the cost of gas, maybe $20 for a different head that might or might not work (if I could find the right one), and then the time to swap the units, so I'd call it a push. In addition the odo still reads the same so my little book of milage vs. maint. items is still accurate without adding/subtracting some fudge factor. While doing all of this, I noticed something that has me a bit puzzled. On the left side of the odometer shaft (to the right of the 100Ks digit when looking at the speedo from the back) is a set of gears and a cam that operates a micro switch which has two wires that exit the instrument cluster through the printed circuit board. The colors of the wires are lt. green and blue/green stripe. I cannot find these wires on any diagrams I have (but I don't have a FSM). Anyone know what this is for?? The car is my '87 3-door spfi. Quote Link to comment Share on other sites More sharing options...
MilesFox Posted July 23, 2005 Share Posted July 23, 2005 i have seen this on an 87 carb cluster. i think it trips at a set mileage to throw the check engine light, to remind you of routine maintenance schedule as far as grease in the speedo head, check the seal where the cable meets the tranny, as when the seal goes bad it will draw diff oil up through the cable. without checking the seal its likely this will occur again Quote Link to comment Share on other sites More sharing options...
Petersubaru Posted July 23, 2005 Share Posted July 23, 2005 my old 86 did that 3 yrs after it was new... Car is '87 3-door EA82 spfi. Mechanical speedometer reads high (pegs) as soon as I get to about 10mph! Odometer and trip counter update correctly. I've not done anything with it yet. I'd like to know what I'm dealing with before tearing the instrument panel out. Does anyone know what causes this and how to fix? Or do I need another instrument cluster?? Quote Link to comment Share on other sites More sharing options...
All_talk Posted July 25, 2005 Share Posted July 25, 2005 About the micro switch... I know the carb cars have a EGR light that is triggered by mileage, not sure about the FI cars. Gary Quote Link to comment Share on other sites More sharing options...
hooziewhatsit Posted July 25, 2005 Share Posted July 25, 2005 About the micro switch... I know the carb cars have a EGR light that is triggered by mileage, not sure about the FI cars. Gary my 85 EA82T wagon had this switch, but I don't think my other two spfi cars have it. Quote Link to comment Share on other sites More sharing options...
NorthWet Posted July 25, 2005 Share Posted July 25, 2005 RE: the micro-switch - the digi-dash that I have taken apart has a similar arrangement, and it seems to be used for determining speed electronically. I suspect that its use on the non-digis is for cruise control, etc. Quote Link to comment Share on other sites More sharing options...
All_talk Posted July 25, 2005 Share Posted July 25, 2005 The FI cars (with ECU), do have a Vehicle Speed Sensor (VSS) in the speed-O head. It could be a simple pulse from a micro switch but I would think it would need at least a few pulses per second even at low speed to have enough resolution. Could the switch in question provide that kind of frequency? I figured the VSS was optical but I really dont know. If I remember correctly the EGR light mileage interval on the carbed cars is 60,000 miles. Gary Quote Link to comment Share on other sites More sharing options...
hooziewhatsit Posted July 25, 2005 Share Posted July 25, 2005 The FI cars (with ECU), do have a Vehicle Speed Sensor (VSS) in the speed-O head. It could be a simple pulse from a micro switch but I would think it would need at least a few pulses per second even at low speed to have enough resolution. Could the switch in question provide that kind of frequency? I figured the VSS was optical but I really dont know. If I remember correctly the EGR light mileage interval on the carbed cars is 60,000 miles. Gary when I had my digi-dash apart, I found the optical sensor they use for the speed signal. There is a small disk with a lot of tiny slots in the outer edge driven by the speedo cable. An opto-isolator 'shoots' through the gaps and creates pulses for the gauge. Quote Link to comment Share on other sites More sharing options...
All_talk Posted July 25, 2005 Share Posted July 25, 2005 when I had my digi-dash apart, I found the optical sensor they use for the speed signal. There is a small disk with a lot of tiny slots in the outer edge driven by the speedo cable. An opto-isolator 'shoots' through the gaps and creates pulses for the gauge. Thats exactly what I was expecting for the VSS. I'm betting the micro switch on the odometer is for the EGR light trip or something similar. Gary Quote Link to comment Share on other sites More sharing options...
NorthWet Posted July 25, 2005 Share Posted July 25, 2005 Yep, VSS it was a slotted opti-sensor. I shouldn't post while not quite awake. Quote Link to comment Share on other sites More sharing options...
TahoeFerrari Posted July 26, 2005 Author Share Posted July 26, 2005 Re: microswitch Yes, I think you are all right about it being some kind of milage trigger - this is a CA car from day 1 and the micro switch is tripped by a cam that looks like is geared about 2:1 from the odometer shaft - that is 1 pulse every 2 miles which could never be used for VSS. You have also pretty much answered my next question: "What does VSS look like". I've access to 2 same-year donor cars (both GL-10s with digi instruments) as my 3-door and I'm going to try to retrofit my 3-door with cruise from one of them, but my '87 has analog instruments. My only real concern is the VSS part of it all. Quote Link to comment Share on other sites More sharing options...
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