Dvlfflr Posted October 6, 2016 Share Posted October 6, 2016 Hey guys,new to the site. I've got an 88 Comanche that has been converted with 99 Cherokee. All running gear, interior and front end have been swapped. The PO didn't swap wiring harness for fuel sender or rear lights. My question is can I swap just the potentiometer on sending units and make my fuel gauge work correctly? I have a complete 2000 Dakota tank,sender that I could swap in but was looking for the easiest fix as my MJ tank is good. Link to comment Share on other sites More sharing options...
johnj92131 Posted October 6, 2016 Share Posted October 6, 2016 What instrument cluster is in your truck? A full 99 cluster and OBD II harness? Link to comment Share on other sites More sharing options...
Dvlfflr Posted October 6, 2016 Author Share Posted October 6, 2016 Yes John, it's all converted to 99 Cherokee dash gauge cluster and wiring. I was told by PO yesterday that he didn't swap the rear harness to run fuel sender and rear lights, I'm unsure if that is a simple plug and play or not. Was hoping to be able to maybe just swap the 99 resistor onto the 88 pump assembly Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 6, 2016 Share Posted October 6, 2016 The pots of the Renix (and HO) fuel sending units are spot welded to the housing so it would be difficult to swap in a different pot even if you could find one. The voltage polarity output and ohms rating (low resistance to high = empty-to-full reading or vice-versa) of the tank sender must also match closely what is required by your 99 fuel gauge for the gauge to read correctly. The Renix and HO sender pots are polarity opposites so one or the other might be close enough for accurate readings if the pot ohms are close enough. Either sending unit will fit in your MJ tank. The HO sender puts out 105 ohms for empty and 5 ohms for full. I don't know what the Renix pot value is; it's close to the HO's but of opposite polarity. Someone will probably chime in with the Renix values. So first thing you need to do is find out the resistance and polarity of the 99 XJ fuel sender pot (it's in the FSM) and match that as close as possible with either an HO or Renix sender. Clear as mud? :yes: EDIT: I just saw over on NAXJA that the 98 XJ sender ohms scale is the below. I have no idea if this is correct and/or if the 98 and 99 senders are the same. If this data is correct, the Renix sender is the correct polarity, but the ohms value will be off. How "off" this will show up on your gauge I don't know. Hook up your existing Renix sender to input your 99 dash fuel gauge and see how accurate it reads.......... Jeep sender, from FSM:With float in up position, resistanceshould be 20 ohms (+/- 5%). With float in downposition, resistance should be 270 ohms (+/- 5%) Link to comment Share on other sites More sharing options...
Eagle Posted October 6, 2016 Share Posted October 6, 2016 The pots of the Renix (and HO) fuel sending units are spot welded to the housing so it would be difficult to swap in a new pot. The voltage polarity output and ohms rating (low resistance to high = empty-to-full reading or vice-versa) of the tank sender must also match closely what is required by your 99 fuel gauge for the gauge to read correctly. The Renix and HO sender pots are polarity opposites so one or the other might be close enough for accurate readings if the pot ohms are close enough. Either sending unit will fit in your MJ tank. The HO sender puts out 105 ohms for empty and 5 ohms for full. I don't know what the Renix pot value is; it's close to the HO's but of opposite polarity. Someone will probably chime in with the Renix values. So first thing you need to do is find out the resistance and polarity of the 99 XJ fuel sender pot (it's in the FSM) and match that as close as possible with either an HO or Renix sender. Clear as mud? :yes: E... The Renix era sender was 0 ohms for empty and 88 ohms for full. Not perfect, but considering how inaccurate (or perhaps "imprecise") a factory fuel gauge is, I think it's something one could learn to live with. The real problem is the reversal of polarity. I've pondered ways to correct that, and the only way I can think of that would work would be to cut the two traces for the fuel gauge on the cluster printed circuit, and run wires from the cluster connector to the opposite terminals on the gauge. Link to comment Share on other sites More sharing options...
Dvlfflr Posted October 7, 2016 Author Share Posted October 7, 2016 Thanks guys, your right clear as mud! ill have to pull senders and check ohm readings, then find where PO cut wiring harness going to rear. Wheew lots of work sounds like! Link to comment Share on other sites More sharing options...
shelbyluvv Posted October 7, 2016 Share Posted October 7, 2016 What you are trying to explain makes zero sense. I did a 97+ swap and you HAVE to run the wiring for the XJ lights and pump. Unless he butchered the harness, the wiring is there. It is all in the harness. Link to comment Share on other sites More sharing options...
Dvlfflr Posted October 7, 2016 Author Share Posted October 7, 2016 Ok then, where can I find 99's wiring schematics or some good quality pics of the wiring harness and wire colors for this sender? Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 7, 2016 Share Posted October 7, 2016 Invest in an Electrical FSM. Link to comment Share on other sites More sharing options...
Dvlfflr Posted October 8, 2016 Author Share Posted October 8, 2016 In the works hornrod, got a buddy that has one. Link to comment Share on other sites More sharing options...
87MJTIM Posted October 8, 2016 Share Posted October 8, 2016 Ok then, where can I find 99's wiring schematics or some good quality pics of the wiring harness and wire colors for this sender? You can find a Factory Service Manual (FSM) on Morris4x4center.com Scroll to the bottom of the left side column for Knowledge Base. The second section in the center is Online Repair Manuals. In the pull down box, select Jeep Cherokee, the year 1996 - 2001. The categories have different sections to the FSM. Find the section you need and download the pdf. Link to comment Share on other sites More sharing options...
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